DSC 2920 CE Operator's Manual · If you are conducting a subambient test on the DSC, cold could...

TA INSTRUMENTS DSC 2920 CE i

DSC 2920 CE

Differential Scanning Calorimeter

Operator’s Manual

PN 815008.001 Rev. E (Text and Binder)PN 815008.002 Rev. E (Text Only)Issued November 1998

TA Instruments

Thermal Analysis & Rheology

A SU B S I D I A R Y O F WATERS C O R P O R A T I O N

TA INSTRUMENTS DSC 2920 CEii

© 1997, 1998 by TA Instruments109 Lukens DriveNew Castle, DE 19720

Notice

The material contained in this manual is believedadequate for the intended use of this instrument.If the instrument or procedures are used forpurposes other than those specified herein,confirmation of their suitability must be obtainedfrom TA Instruments. Otherwise, TA Instru-ments does not guarantee any results andassumes no obligation or liability. This publica-tion is not a license to operate under or arecommendation to infringe upon any processpatents.

TA Instruments Operating Software and Instru-ment, Data Analysis, and Utility Software andtheir associated manuals are proprietary andcopyrighted by TA Instruments, Inc. Purchasersare granted a license to use these softwareprograms on the instrument and controller withwhich they were purchased. These programsmay not be duplicated by the purchaser withoutthe prior written consent of TA Instruments.Each licensed program shall remain the exclusiveproperty of TA Instruments, and no rights orlicenses are granted to the purchaser other thanas specified above.

TA INSTRUMENTS DSC 2920 CE iii

Table of Contents

Notes, Cautions, and Warnings...............ix

Helplines ......................................................x

Safety............................................................xi

CE Compliance .......................................xi

Instrument Symbols................................xii

Electrical Safety ....................................xiii

Handling Liquid Nitrogen ......................xiv

Chemical Safety .....................................xv

Thermal Safety .....................................xvi

Lifting the Instrument............................xvi

Using This Manual .................................xvii

CHAPTER 1: Introducing theDSC 2920 CE........................................... 1-1

Introduction................................................. 1-3

Components .......................................... 1-4

The 2920 CE Instrument ............................. 1-5

2920 CE Display ................................... 1-6

2920 CE Keypad .................................. 1-7HEATER Switch ........................... 1-9POWER Switch ............................. 1-9

TA INSTRUMENTS DSC 2920 CEi v

Table of Contents(continued)

Standard DSC Cell .............................1-10

Dual Sample DSC Cell .......................1-11

Accessories........................................1-12Sample Encapsulating Press ........1-12DSC Autosampler ........................1-13Accessories forSubambient Operation ..................1-13

Heat Exchanger ....................1-13LNCA ...................................1-13RCS .......................................1-14DSC Cooling Can ..................1-15

Specifications ............................................1-16

CHAPTER 2: Installingthe DSC 2920 CE ........................................... 2-1

Unpacking/Repacking the 2920 CE ................... 2-3

Unpacking the 2920 CE .............................. 2-3

Repacking the 2920 CE .............................. 2-6

Installing the Instrument .................................... 2-7

Inspecting the System ................................. 2-7

Choosing a Location.................................... 2-8

Connecting Cables and Gas Lines .............. 2-9

GPIB Cable .......................................... 2-9Purge, Vacuum, andCooling Gas Lines...............................2-12

TA INSTRUMENTS DSC 2920 CE v


PURGE Line ...............................2-12VACUUM Line...........................2-13COOLING GAS Line ..................2-13

Power Cable .......................................2-14

Installing the Standard andDual Sample DSC Cells ..................................2-16

Installations for Subambient Operation ............2-20

Installing the DSC Cooling Can ................2-21

Starting the 2920 CE ..................................2-23

Shutting Down the 2920 CE ............................2-25

CHAPTER 3: Running Experiments......... 3-1

Overview ....................................................... 3-3

Before You Begin ....................................... 3-3

Calibrating the DSC........................................... 3-4

Baseline Slope andOffset Calibration ........................................ 3-5

Cell Constant Calibration ............................ 3-6

Temperature Calibration ............................. 3-7

Crosstalk Calibration ................................... 3-7

Running a DSC Experiment .............................. 3-8

Experimental Procedure .............................. 3-8

TA INSTRUMENTS DSC 2920 CEv i


Preparing Samples .................................... 3-9

Determining Sample Size...................... 3-9Physical Characteristics .....................3-10

Selecting Sample Pans .................3-11Sample Pan Material .............3-11Sample Pan Configuration .....3-13

Nonhermetic Pans ..........3-13Hermetic Pans ................3-13Open Pans ......................3-14SFI Pans .........................3-14

Encapsulating the Sample .............3-15Preparing NonhermeticSample Pans ..........................3-16Preparing HermeticSample Pans ..........................3-19

Setting Up an Experiment .........................3-22

Setting Up Accessories ......................3-24

Loading the Sample ............................3-27

Starting an Experiment .......................3-28

Stopping an Experiment ......................3-28

Subambient Experiments ...........................3-30

DSC Cooling Can ...............................3-30

Applications..................................3-30Operation ......................................3-31

Quench-CoolingBetween Runs .......................3-31Starting a Run BelowAmbient Temperature ...........3-32

TA INSTRUMENTS DSC 2920 CE vii


CHAPTER 4: Technical Reference....4-1

Description of the DSC 2920 CE ................ 4-3

DSC Standard and DualSample Cells ......................................... 4-4

Principles of Operation ............................... 4-6

Cell Block Heating ............................... 4-6

Sample and ReferenceThermocouples ..................................... 4-7

DSC Applications ........................................ 4-8

Sample Types ....................................... 4-8

Status Codes ............................................... 4-9

Guidelines for Quantitative Studies ...........4-13

Specific Heat Experiments .................4-13

CHAPTER 5: Maintenance andDiagnostics................................................5-1

Overview ....................................................5-3

Routine Maintenance ..................................5-4

Inspection .............................................5-4

Cleaning the Instrument .......................5-4

Cleaning a Contaminated Cell ..............5-5

TA INSTRUMENTS DSC 2920 CEviii


Cleaning DSC Pans.............................. 5-6

Sample Encapsulating Press.................5-7

Diagnosing Power Problems .......................5-8

Fuses .................................................... 5-8

Furnace Power Check .....................5-9

Heater Indicator Light ........................5-10

Power Failures ...................................5-11

DSC 2920 CE Test Functions ...................5-12

The Confidence Test ..........................5-12

Replacement Parts ....................................5-15

APPENDIX A: SampleEncapsulating Press...............................A-1

APPENDIX B: OrderingInformation ............................................... B-1

APPENDIX C: ModulatedDSCTM Option .......................................... C-1

INDEX ....................................................... I-1

DSC 2920 CE Pressure Cell .............PDSC-1

DSC 2920 CE 1600°C DTA Cell .......DTA-1

TA INSTRUMENTS DSC 2920 CE ix

Notes, Cautions,and Warnings

This manual uses NOTES, CAUTIONS, andWARNINGS to emphasize important and criticalinstructions.

A WARNING indicates a procedure that may behazardous to the operator or to the environ-ment if not followed correctly.

A CAUTION emphasizes a procedure that maydamage equipment or cause loss of data if notfollowed correctly.

A NOTE highlights important information aboutequipment or procedures.

!WARNING

uuuuu CAUTION:

NOTE:

TA INSTRUMENTS DSC 2920 CEx

Helplines

To TA Instruments

For Technical Assistance......... (302) 427-4070

To Order Instruments andSupplies.................................... (302) 427-4040

For Service Inquiries ................ (302) 427-4050

Sales ......................................... (302) 427-4000

TA INSTRUMENTS DSC 2920 CE xi

SafetyThis equipment has been designed to complywith the following standards on safety:• IEC 1010-1/1990 + A1/1992 + A2/1995• IEC 1010-2-010/1992 + A1/1996• EN 61010-1/1993 + A2/1995• EN 61010-2-010/1994• UL 3101-1, First Edition.

CE Compliance

In order to comply with the ElectromagneticCompatibility standards of the European CouncilDirective 89/336/EEC (EMC Directive) andDirective 73/23/EEC on safety as amended by93/68/EEC, the following specifications apply tothe DSC 2920 CE instrument:

• Safety:EN 61010-1/1993 + A2/1995 InstallationCategory IIEN 61010-2-010/1994

• Emissions:EN 55022: 1995, Class B (30–1000 MHz)radiatedEN 55022: 1995, Class B (0.15–30 MHz)conducted

• Immunity:EN 50082-1: 1992 ElectromagneticCompatibility—Generic immunity standardPart 1. Residential, commercial, and lightindustry.— IEC 801-2: 1991, 8 kV air discharge.— IEC 801-3: 27–500MHz, 3V/m. No

response above 10µW (55 nV) heatflow (∆E

t) and 0.01°C sample

temperature.— IEC 801-4: 1988 Fast transients com-

mon mode 1kV AC power.

TA INSTRUMENTS DSC 2920 CEx i i

Safety(continued)

Instrument Symbols

The following labels are displayed on the DSC2920 CE instrument for your protection:

Symbol Explanation

This symbol, whichappears on the metal belljar and the heat exchangerouter can of the DSC2920 CE, indicates that ahot surface may bepresent. Take care not totouch these areas or allowany material that may meltor burn to come in contactwith these hot surfaces.

Please heed the warning labels and take thenecessary precautions when dealing with thoseparts of the instrument. The DSC 2920 CEOperator's Manual contains cautions andwarnings that must be followed for your ownsafety.

TA INSTRUMENTS DSC 2920 CE xiii

!WARNING

Safety(continued)

Electrical Safety

The hold-down thumbscrews that hold the DSCcell in place enable the AC power interlock forthe cell. You cannot run experiments withoutthem. If they are not fully in place, the instru-ment will not be able to apply power to the celland will not operate.

You must unplug the instrument before doing anymaintenance or repair work; voltages exceeding110 volts AC are present in this system.

High voltages are present in this instrument. Ifyou are not trained in electrical procedures, donot remove the cabinet covers. Maintenanceand repair of internal parts must be performedonly by TA Instruments or other qualifiedservice personnel.

An isolation transformer should be used whentroub leshoot ing .*

After transport or storage in humid conditions, thisequipment could fail to meet all the safety requirements ofthe safety standards indicated. Refer to the NOTE onpages 2-8 to 2-9 for the method of drying out theequipment before use.

* Test equipment may connect the instrument toground, rendering the Isolation Transformer ineffec-tive. There are low voltage circuits in this equipmentthat are referenced to hazardous voltages.

!WARNING

!WARNING

TA INSTRUMENTS DSC 2920 CEx i v

Safety(continued)

Handling Liquid Nitrogen

The DSC 2920 CE uses the cryogenic (low-temperature) agent, liquid nitrogen, for cooling.Owing to its low temperature –195°C (–319°F),liquid nitrogen will burn the skin. When you workwith liquid nitrogen, use the following precau-tions:

Liquid nitrogen evaporates rapidly at roomtemperature. Be certain that areas whereliquid nitrogen is used are well ventilated toprevent displacement of oxygen in the air.

1. Wear goggles or a face shield, gloves largeenough to be removed easily, and a rubberapron. For extra protection, wear hightopped,sturdy shoes, and leave your pant legsoutside the shoe tops.

2. Transfer the liquid slowly to prevent thermalshock to the equipment. Use containers thathave satisfactory low-temperature proper-ties. Ensure that closed containers havevents to relieve pressure.

3. The purity of liquid nitrogen decreases as thenitrogen evaporates. If much of the liquid ina container has evaporated, analyze theremaining liquid before using it for anypurpose for which high oxygen content couldbe dangerous.

!WARNING

TA INSTRUMENTS DSC 2920 CE xv

Safety(continued)

IF A PERSON IS BURNED BY LIQUIDNITROGEN . . .

1. IMMEDIATELY flood the area (skin oreyes) with large quantities of cool water, andthen apply cold compresses.

2. If the skin is blistered or if there is a chanceof eye infection, take the person to a doctorIMMEDIATELY.

Chemical Safety

Do not use hydrogen or any other explosive gaswith the DSC 2920 CE.

Use of chlorine gas will damage the cell.

Cell life will be shortened if an oxidizing atmosphere isused above 450°C for extended periods.

If you are using samples that may emit harmful gases,vent the gases by placing the DSC near an exhaust. Thevacuum fitting can be used to directly connect to the cellenvironment.

If oxygen is used as a purge gas, the cell must be free ofany combustible contaminants in order to avoid anenergetic reaction. We recommend that the cell be�cleaned� in an air atmosphere, as described on page 5-5for cleaning a contaminated cell, prior to operating with anoxygen-rich atmosphere.

!WARNING

!WARNING

uuuuu CAUTION:

uuuuu CAUTION:

!WARNING

TA INSTRUMENTS DSC 2920 CExv i

Safety(continued)

Thermal Safety

The cell surfaces and metal bell jar can be hotenough to burn the skin during a sample run.Allow the cell surfaces to cool to ambienttemperature before you touch them.

If you are conducting a subambient test on theDSC, cold could also cause injury. After runningany type of experiment, you must allow the DSCcell to return to room temperature before youtouch the inner cell surfaces.

Lifting the Instrument

The DSC 2920 CE is a fairly heavy instrument.In order to avoid injury, particularly to the back,please follow this advice:

Use two people to lift and/or carry the instru-ment. The instrument is too heavy for oneperson to handle safely.

!WARNING

TA INSTRUMENTS DSC 2920 CE xvii

Using This Manual

Chapter 1 Describes the DSC 2920CE and its specifications.

Chapter 2 Describes how to connectthe DSC 2920 CE to therest of your system andinstall the various celltypes.

Chapter 3 Describes how to runDSC and Dual Sampleexperiments.

Chapter 4 Provides technical infor-mation, principles ofoperation for the cells, andguidelines.

Chapter 5 Describes instrumentmaintenance proceduresand the confidence testcodes.

Appendix A Explains how to changethe Sample EncapsulatingPress dies.

Appendix B Lists worldwide TAInstruments offices thatyou can contact to placeorders, receive technicalassistance, and requestservice.

TA INSTRUMENTS DSC 2920 CExviii

Using This Manual(continued)

Appendix C Tells you how to use theModulated DSCTM option.

Index Lists the page numbers ofimportant topics for yourreference.

TA INSTRUMENTS DSC 2920 CE xix

Potential Asphyxiant

Liquid nitrogen can cause rapid suffocation withoutwarning.

Store and use in an area with adequate ventilation.

Do not vent LNCA container in confined spaces.

Do not enter confined spaces where nitrogen gasmay be present unless the area is well ventilated.

The warning shown above applies to the use of liquid nitrogen.Oxygen depletion sensors are sometimes utilized where liquidnitrogen is in use. Please refer to the �Safety� section of the TAInstruments Liquid Nitrogen Cooling Accessory manual for moredetailed instructions regarding the use of the LNCA.

!WARNING

TA INSTRUMENTS DSC 2920 CEx x

TA INSTRUMENTS DSC 2920 CE 1�1

CHAPTER 1: Introducing theDSC 2920 CE

Introduction................................................. 1-3

Components .......................................... 1-4

The 2920 CE Instrument ............................. 1-5

2920 CE Display ................................... 1-62920 CE Keypad .................................. 1-7

HEATER Switch ........................... 1-9POWER Switch ............................. 1-9

Standard DSC Cell .............................1-10Dual Sample DSC Cell .......................1-11

Accessories........................................1-12Sample Encapsulating Press ........1-12DSC Autosampler ........................1-13Accessories forSubambient Operation ..................1-13

Heat Exchanger ....................1-13LNCA ...................................1-13RCS .......................................1-14DSC Cooling Can ..................1-15

Specifications ............................................1-16

Introducing the DSC 2920 CE

1�2 TA INSTRUMENTS DSC 2920 CE


Introduction

The Differential Scanning Calorimeter (DSC)2920 CE determines the temperature and heatflow associated with material transitions as afunction of time and temperature. It also provi-des quantitative and qualitative data on endo-thermic (heat absorption) and exothermic (heatevolution) processes of materials during physicaltransitions that are caused by phase changes,melting, oxidation, and other heat-relatedchanges. This information helps the scientist orengineer identify processing and end-use perfor-mance.

The DSC 2920 CE instrument works in conjunc-tion with a controller and associated software tomake up a thermal analysis system.

Your controller is a computer that performs thefollowing functions:

• Provides an interface between you and theanalysis instruments

• Enables you to set up experiments and enterconstants

• Stores experimental data• Runs data analysis programs.

Introduction



ComponentsThe DSC 2920 CE (see Figure 1.1) has twomajor parts: the 2920 CE instrument, whichcontains the system electronics, and the cell,which contains its own thermocouples (tempera-ture sensor) for monitoring differential heat flowand temperature. Two interchangeable cell typesare available:

• Standard DSC Cell• Dual Sample DSC Cell

Figure 1.1 identifies the parts of the instrument.

Figure 1.1DSC 2920 CE

M e t a lBell Jar


The 2920 CEInstrument

The DSC 2920 CE contains the electronics andsoftware needed to perform experiments andstore experimental results. The battery-backed-up RAM in the instrument saves parameters vitalto system operations if power is interrupted. Alsocontained in the instrument is a GPIB interfacefor communication with the controller.

The keypad on the front of the DSC 2920 CEenables you to start and stop experiments. Thedisplay above the keypad provides realtimeinformation about the experiment.

The DSC 2920 CE also contains several hook-ups for other components and accessories in thethermal analysis system, including:

• Gas purge• Cool-down line• Vacuum• LNCA (Liquid Nitrogen Cooling Accessory)• Gas Switching Accessory• EVENT relay• GPIB• Power cable.

The 2920 CE Instrument



Figure 1.2DSC 2920 CEDisplay and Keypad

2920 CE Display

The DSC 2920 CE display is the lighted areaabove the keypad (see Figure 1.2). It containstwo rows of 20 characters each.

During normal operation, the display is seg-mented into three areas. The left eight charac-ters on the upper line show the instrument status;the right nine characters show the sampletemperature; and the bottom line is a realtimesignal display. Status codes are described in theTechnical Reference chapter of this manual.

DSC 2920 CE Differential Scanning Calorimeter

Standby 23.25°CHtFlow 0.012 mW



Table 1.1DSC 2920 CE KeypadFunction Keys

(table continued)

NOTE :

2920 CE Keypad

The instrument keypad (see Figure 1.2) containsthe keys found in Table 1.1 and the HEATERand POWER switches:

Experiment information and instrument con-stants are entered from the controller key-board, not the instrument keypad.

Key/Function Explanation

SCROLL Scrolls the realtime signalsshown on the bottom lineof the display. For moreinformation on theprogress of the experi-ment, refer to the statusand signal displays on thecontroller.

START Initiates the experimentafter the method ischecked against the celltype. This is the samefunction as Start on thecontroller.

STOP If an experiment isrunning, this key ends themethod normally, asthough it had run tocompletion; i.e., themethod-end conditionsselected go into effect,and the data that has beengenerated is saved. Thisis the same function asStop on the controller.



Table 1.1DSC 2920 CEKeypad Function Keys(continued)

If an experiment is notrunning (the instrument isin a stand-by or method-end state), STOP haltsany activity (air cool,LNCA auto-fill, etc.).

REJECT If an experiment isrunning, SCROLL-STOP ends the method

(Hold down normally, as though itSCROLL and had run to completion;press STOP) i.e., the method-end

conditions go into effect,and the data that has beengenerated is discarded.This is the same functionas Reject on the control-ler.

NOTE: The SCROLL key operatesnormally (scrolls therealtime signals) until theSTOP key is pressed.

If an experiment is notrunning, SCROLL-STOPworks like the STOP key.


HEATER SwitchThe HEATER switch (see Figure 1.2) turns thepower to the instrument heater on and off. Theswitch should be in the ON (1) position beforeyou start an experiment.

The heater light will glow whenever the powercontrol circuits are enabled. This occurs wheneither a method is running or an end of methodfunction (return to temp range or auto-samplerload window) is selected and active. (See"Heater Indicator Light" in Chapter 5 for moreinformat ion . )

POWER SwitchThe POWER switch (see Figure 1.2) turns thepower to the DSC 2920 CE on and off.

NOTE:




Standard DSC Cell

The standard DSC Cell (Figure 1.3) is used tomeasure differential heat flow. The sample and areference are placed in pans that sit on raisedplatforms on a constantan disk, and heat istransferred through the disk up into the sampleand reference. The differential heat flow ismonitored by thermocouple wires welded to thedisk.

Figure 1.3DSC 2920 CE withStandard DSC Cell

In this manual, the il lustrations for the DSC Celldepict a glass bell jar. However, a metal belljar is used in the CE version.

NOTE:


Dual Sample DSC Cell

The Dual Sample DSC (DSDSC) Cell (Figure1.4) is a cell which is capable of analyzing twosamples simultaneously. It performs all of thesame functions as the standard cell on the twosamples placed inside. Inside the cell, the twosamples sit on raised platforms on a constantandisk. Heat is transferred through the disk to thesamples and reference.

Figure 1.4Top View ofDual Sample DSC Cell



1�12 TA Instruments DSC 2920 CE

Accessories

Sample Encapsulating Press

The TA Instruments Sample EncapsulatingPress (Figure 1.7) is used to prepare encapsu-lated samples for DSC experiments. It comeswith two sets of dies, one for hermetic and onefor non-hermetic sealing.

Figure 1.5SampleEncapsulatingPress

TA Instruments DSC 2920 CE 1�13

DSC Autosampler

The DSC Autosampler automatically loadssample and reference pans to the DSC, allowsthe programmed experiment to finish, thenunloads the pans and begins the next experiment.

Accessories forSubambient Operation

The DSC 2920 CE can be operated at below-ambient temperatures using one of the coolingaccessories such as the Liquid Nitrogen CoolingAccessory (LNCA), the Refrigerated CoolingSystem (RCS), or the DSC Cooling Can.

Heat Exchanger

The heat exchanger works in conjunction withthe LNCA to cool down samples on the 2920CE. The heat exchanger fits over the standardand dual sample DSC cells.

LNCAThe LNCA provides automatic and continuousprogrammed sample cooling within the range of–150°C to 725°C when used with the DSC heatexchanger installed on the DSC Cell (refer tothe LNCA Operator’s Manual for installation).Heaters vaporize the liquid nitrogen in the LNCAtank. The cool gas is forced up and mixed withliquid nitrogen. The gas/liquid mix is delivered tothe heat exchanger to cool the cell.

Accessories



Refrigerated Cooling System (RCS)

The Refrigerated Cooling System (RCS), whichis used to cool DSC experiments, consists of atwo-stage, cascade, vapor compression refrig-eration system with an attached cooling head.The cooling head fits over the RCS-DSC cell foruse with the DSC 2920 CE. The RCS can beused for experiments requiring cooling within anoperating range of–70°C to 400°C. The maxi-mum rate of cooling depends on the temperaturerange of your experiment.

Figure 1.6Refrigerated CoolingSystem


DSC Cooling Can

The DSC Cooling Can fits over the standardDSC Cell and has a reservoir into which you canplace coolant to quench cool the cell.

Figure 1.7DSC Cooling Can

Accessories

Open-top Bell Jar

Aluminum Spacer

Cooling Can

Split O-ringDSC Cell



Specifications

Tables 1.2 through 1.4 contain the technicalspecifications for the DSC 2920 CE and its celltypes.

Dimensions Depth 45.5 cm (18 in.)Width 58.5 cm (23 in.)Height 49.5 cm (19.5 in.)

Weight(approx.) 22 kg (48 lb)

Power 120 volts AC +10%50/60 Hz1000 VA

Room 15°C to 30°Coperatingtemperature

Insulation All electrical insulationrating between hazardous

components and SELV(Separated Extra LowVoltage) circuits havebeen designed to meet therequirements of reinforcedinsulation as defined byIEC-950 and specifiedinIEC-1010.

* Only values with tolerances or limits are guaran-teed data. Values without tolerances are forinformation only.

Table 1.2DSC 2920 CE Specifications*


Table 1.3Standard DSCCell Specifications

Dimensions Depth 24 cm (9.5 in.)Width 13.5 cm (5.3 in)Height 18.8 cm (7.4 in.)

Weight 1.7 kg (3.5 lb)(approx.)

Temperature Room temperature to 725°Crange (inert atmosphere above

600oC) as supplied; to–150oC with the LNCA andDSC Cooling Can; –70°C to–400°C with RCS.

Cell life will be shortened if anoxidizing atmosphere is usedabove 450°C for extendedperiods.

Cooling rate Dependent on accessoryused and temperature range

Sample size 0.5 to 100 mg (nominal)

Sample volume 10 mm3 in hermetic pans

Sample pans Various open or hermeti-cally sealed

Atmosphere Atmospheric to 266 Pa (2torr); preheated dynamicgas purge (200 ml/minmaximum)

Purge gases Recommended: air, argon,helium, nitrogen, or oxygen

Typical flow 25–50 mL/minrate

(table continued)

Specifications

uuuuu CAUTION:



Cell volume 2 cm3

Temperature +0.1°Crepeatability

Differential CHROMEL®*-constantanthermocouples (Type E)

Sample CHROMEL-ALUMEL®*(Type K)

thermocouple

Control Platenel II**thermocouple

Calorimetric 0.2 µW (rms)sensitivity

Constant + 2.5% from –100°C tocalorimetric to500oCsensitivity

Calorimetric 1% (based on metalprecision samples)

Baseline noise 0.1 µW (rms)

* CHROMEL® and ALUMEL® areregistered trademarks of HoskinsManufacturing Company.

** Platinel is a registered trademark ofEngelhard Industries.

Table 1.3Standard DSCCell Specifications(continued)


Table 1.4Dual SampleCell Specifications

Dimensions Depth 24 cm (9.5 in.)Width 13.5 cm (5.3 in)Height 18.8 cm (7.4 in.)

Weight 1.7 kg (3.5 lb)(approx.)

Other specifications similar to those of thestandard DSC cell. Performance depends onpressure and atmosphere selected. Subambi-ent baseline performance of the dual samplecell may not be comparable to that of thestandard DSC cell.




CHAPTER 2: Installing theDSC 2920 CE

Unpacking/Repacking the 2920 CE ................... 2-3

Unpacking the 2920 CE .............................. 2-3

Repacking the 2920 CE............................... 2-6

Installing the Instrument .................................... 2-7

Inspecting the System .................................. 2-7

Choosing a Location ................................... 2-8

Connecting Cables and Gas Lines ............... 2-9

GPIB Cable .......................................... 2-9Purge, Vacuum, andCooling Gas Lines .............................. 2-12

PURGE Line ................................ 2-12VACUUM Line ........................... 2-13COOLING GAS Line .................. 2-13

Power Cable ....................................... 2-14

Installing the Standard andDual Sample DSC Cells .................................. 2-16

Installations for Subambient Operation ........... 2-20

Installing the DSC Cooling Can ................ 2-21

Starting the 2920 CE ....................................... 2-23

Shutting Down the 2920 CE ............................ 2-25

Installing the 2920 CE



Unpacking/Repackingthe 2920 CE

These instructions are also found as separate unpackinginstructions in the shipping box.

You may wish to retain all of the shippinghardware, the plywood, and boxes from theinstrument for reuse if you want to repack andship your instrument.

Unpacking the 2920 CE

Have an assistant help you unpack this unit. Do not attemptto do this alone.

Figure 2.1Shipping Boxes

NOTE:

Unpacking/Repacking the 2920 CE

!WARNING



1. Open the shipping carton and remove theaccessory box.

2. Remove the cardboard packing insert.

3. Stand at one end of the box with yourassistant facing you at the other end. Liftyour end of the unit out of the box as yourassistant lifts his/her end.

4. Place the unit on a lab bench with one sidehanging over the edge of the bench (seeFigure 2.2). Someone must be holding ontothe unit at all times while it is in thisposition.

Figure 2.2Removing the PlywoodBoard

5. While your assistant holds the unit, use awrench to remove the two nuts and washersfrom the bottom. Then lift and rotate the unitso that the other end hangs over the edge ofthe bench. Someone must hold onto the unitat all times while it is in this position.


While your assistant holds the unit, removethe two nuts and washers from the other side.

6. Have your assistant lift the entire unit whileyou slide the plywood board out from underit.

7. Slide the unit completely onto the lab bench.Have your assistant hold one side up whileyou unscrew and remove the black rubbershipping feet from the bottom. Then rotatethe unit and remove the shipping feet fromthe other side in the same manner.

8. Have your assistant lift one side of the unitwhile you use a wrench to install two mount-ing feet (see Figure 2.3). Rotate the unit andinstall the two remaining mounting feet in thesame manner.

Figure 2.3 Installingthe Mounting Feet

Unpacking/Repacking the 2920 CE



Repacking the 2920 CE

To pack and ship your instrument, use thehardware retained during unpacking and reversethe instructions found on pages 2-3 to 2-5.


Installingthe Instrument

Before shipment, the DSC 2920 CE is inspectedboth electrically and mechanically so that it isready for operation after it has been installed.Installation involves the following procedures,described in this chapter:

• Inspecting the system for shipping damageand missing parts

• Connecting the instrument to a PC-basedcontroller

• Connecting the gas and vacuum lines,accessories, and power cable

• Installing the desired cell type.

If you wish to have your DSC 2920 CE installedby a TA Instruments Service Representative, callfor an installation appointment when you receiveyour instrument.

Inspectingthe System

When you receive your DSC 2920 CE, look overthe instrument and shipping container carefullyfor signs of shipping damage, and check the partsreceived against the enclosed shipping list.

• If the instrument is damaged, notify thecarrier and TA Instruments immediately.

• If the instrument is intact but parts aremissing, contact TA Instruments.

The address for the TA Instruments officenearest you can be found in Appendix B of thismanual.

Installing the Instrument



Near

Away from

In

On

Choosinga Location

Because of the sensitivity of DSC experiments, itis important to choose a location for the instru-ment using the following guidelines. The DSC2920 CE should be:

. . . a temperature-controlled area(15°C to 30°C is recommended).

. . . a clean environment.

. . . an area with ample working and ventilationspace. (Refer to the technical specificationsin Chapter 1 for the instrument’s dimen-sions.)

. . . a stable, heat-resistant, and fire-resistantwork surface.

. . . a power outlet (120 Vac, 50 or 60 Hz, 15amps). A step up/down line transformermay be required if the unit is operatedfrom a higher or lower line voltage.

. . . your TA Instruments controller.

. . . a compressed lab air and purge gas supplyfor use during cooling, subambient, andhigh temperature experiments.

. . . dusty environments.

. . . exposure to direct sunlight.

. . . direct air drafts (fans, room air ducts).

. . . poorly ventilated areas.

. . . flammable materials

Drying out the instrument may be needed, if it has beenexposed to humid conditions. Certain ceramic materialsused in this equipment may absorb moisure, causingleakage currents to exceed those specified in the appli-cable standards (see page xi) until the moisture iseliminated. It is important to be certain that the instru-ment ground is adequately connected to the facilitiesground for safe operation.

(continued)

NOTE:


Run the following method to dry out the instrument (referto �Running Experiments� for further information).

1 Ramp at 10°C/min to 400°C2 Isothermal for 30 min.

Connecting Cablesand Gas Lines

To connect the cables and gas lines, you willneed access to the DSC 2920 CE’s rear panel.All directional descriptions are written on theassumption that you are facing the back of theinstrument.

Connect all cables before connecting the power cords tooutlets. Tighten thumbscrews on all computer cables.

Whenever plugging or unplugging power cords, handlethem by the plugs, not by the cords.

Protect power and communications cable paths. Do notcreate tripping hazards by laying cables across accessways.

GPIB Cable

To connect the GPIB cable, follow these direc-tions:

1. Locate the GPIB connector on the right rearof the DSC 2920 CE (see Figure 2.4).

2. Connect the GPIB cable to the connector.The GPIB cable is the only cable that fitsinto the connector.


ttttt CAUTION:

!WARNING

NOTE:(continued)

NOTE:



Cooling AccessoryConnector

ReadyLight

ResetButton

AddressDial

PowerCord

GPIBConnector

3. Tighten the hold-down screws on theconnector.

4. Connect the other end of the GPIB cable tothe controller or to the GPIB cable of anotherTA Instruments instrument connected to thecontroller.

Figure 2.4DSC 2920 CEConnector Panel

5. Select a unique address from 1 to 9 (one thatis not used by any other instruments con-nected to your controller). Then use theaddress selector dial on the DSC 2920 CEconnector panel to set the desired address .Figure 2.5 shows an instrument address of 7.

If you change the address after the instru-ment is powered on, you must press theReset button on the instrument to enter thenew address. Wait 30 seconds after releasingthe Reset button; the green Ready lightshould begin to glow steadily. Then reconfig-ure the instrument with the controller tobring the instrument back online.


Figure 2.5Address Selector Dial(Showing an Address of 7)

If you have a multi-instrument system, each instrumentmust have a different address.

If you change the address after the DSC ispowered on, you must press the DSC’s Resetbutton to enter the new address. Wait until theinstrument completes its startup displays, thenreconfigure the instrument with the controller tobring the instrument back online.

The instrument�s GPIB address is displayed during startupand can also be viewed on the instrument�s status display.


NOTE:

NOTE:



Purge, Vacuum,and Cooling Gas Lines

PURGE Line

The PURGE typically is used to control theenvironment around the sample.

1. Locate the PURGE fitting on the right side ofthe DSC 2920 CE back (see Figure 2.6).

Figure 2.6PURGE andVACUUM Fittings

2. Make sure your purge source is regulatedbetween 5 and 30 psi and connected toa flowmeter to regulate flow up to200 mL/min.

Use of any explosive gas as a purge gas is dangerous and isnot recommended for the DSC 2920 CE.!WARNING


If oxygen is used as a purge gas, the cell must be free of anycombustible contaminants in order to avoid an energeticreaction. We recommend that the cell be �cleaned� in an airatmosphere, as described on page 5-5 for cleaning acontaminated cell, prior to operating with an oxygen-richatmosphere.

Use of corrosive gases will shorten the life of theinstrument and cell.

3. Connect a ¼-inch I.D. flexible tubing purgeline to the PURGE fitting.

VACUUM Line

The VACUUM line is used to help minimize thebuild-up of moisture in the cell during coolingexperiments and to remove gases evolved fromsamples during experiments.

1. Locate the VACUUM fitting on theright side of the DSC 2920 CE back (seeFigure 2.6).

2. Connect a ¼-inch I.D. flexible tubingvacuum line to the VACUUM fitting.

To minimize moisture build-up during subambient experi-ments, supply a dry nitrogen purge to the vacuum line usinga rate of 100�150 mL/min.

COOLING GAS Line

The COOLING GAS line is used to cool theinstrument to ambient temperature.

To prevent vibration of the bell jar, use a split O-ring when you use cooling gas with the standardDSC Cell. A split O-ring is provided with theDSC Cooling Can. If you do not have a split O-ring, you can order one from TA Instruments or


ttttt CAUTION:

!WARNING

NOTE:



modify the one that comes with the DSC Cell.By cutting a small (1 cm) section out of the DSCcell O-ring before placing it under the bell jar,you can prevent possible vibration when usingthe cooling gas with the DSC.

Connect the COOLING GAS line as follows:

1. Locate the COOLING GAS fitting, a ¼-inchcompression fitting on the left side of theDSC 2920 CE back, marked with a 120 psimaximum warning label (see Figure 2.7).

Figure 2.7COOLINGGAS Fitting

2. Make sure your cooling gas source isregulated between 20 and 120 psi.

The COOLING GAS line feeds into a pressure-regulatedvalve that is set to 15 psi. The source pressure settingshould not go below this value.

3. Connect a compressed air line to the COOL-ING GAS fitting.

Power Cable

The DSC 2920 CE accessory kit contains aferrite-loaded power cord. This provides the DSCprotection against electromagnetic interference(EMI). To ensure best test results, the ferrite-

ttttt CAUTION:


loaded power cord must be used with the DSCinstrument.

Connect all other cables and gas lines before connecting thepower cable to a wall outlet.

1. Make sure the DSC 2920 CE POWERswitch (see Figure 2.8) is in the OFF (0)position.

Figure 2.8DSC 2920 CEPOWER Switch

2. Plug the power cable into the DSC 2920 CE.

Before plugging the DSC 2920 CE power cable intothe wall outlet, make sure the instrument is compatiblewith the line voltage. Check the label on the back of theunit to verify the voltage.

3. Plug the power cable into the wall outlet orstep down/up transformer.

The DSC 2920 CE instrument requires the use of special-ized cells. Non�DSC 2920 CE cells are not compatible withthe DSC 2920 CE instrument.


NOTE:

ttttt CAUTION:

NOTE:




Installing theStandard andDual SampleDSC Cells

To install the standard and dual sample DSCcells on the DSC 2920 CE, follow the instruc-tions found in this section. Both cells are in-stalled using the identical procedures. Whenunpacking a cell from its original container,remove and discard all packing material, such astape and polyethylene film.

1. Remove the metal bell jar from the cell youare about to install (see Figure 2.9).

Figure 2.9Standard DSC Cell

DressCan

MetalBell Jar


2. Locate the alignment guides on the instru-ment base as shown in Figure 2.10 below.

Figure 2.10DSC 2920 CECell Base Connectors

3. Slide the DSC Cell onto the instrumentfollowing the alignment guides (see Figure2.11) until the connectors plug into theinstrument.

Air Cool Port

Installing the Standard and Dual Sample Cells



Figure 2.11Sliding the Cellonto the 2920 CE

When the cell is fully mated with the connectors,you will see the following message displayed:

Establishing contact with cell.

Then this message will be displayed:

Contact complete.DSC Standard.

The display then returns to normal.


4. Install the two hold-down thumbscrewsshipped in the DSC 2920 CE accessory kit(see Figure 2.12). Tighten them slowly andevenly with your fingers (do not use a tool)to ensure proper pneumatic connection to thecell.

Tightening down the thumbscrews engages a powerinterlock in the instrument base. No power is supplied to thecell without them. They must be in place to run theinstrument.

Figure 2.12DSC Cell withThumbscrewsin Place

5. Install the O-ring, making sure that it fitsproperly into the groove.

6. Place the bell jar over the cell.

!WARNING

Installing the Standard and Dual Sample Cells



Installations for Subambient Operation(Standard and DualSample DSC Cells Only)

The standard and dual sample DSC cells can beoperated at subambient conditions using any oneof the following cooling accessories:

• Liquid Nitrogen Cooling Accessory (LNCA)with the DSC Heat Exchanger

• DSC Cooling Can.• Refrigerated Cooling System (RCS).

This section describes how to install the CoolingCan on the DSC 2920 CE. Procedures forinstalling the LNCA and the RCS with the DSC2920 CE can be found in the literature accompa-nying those accessories.


Installing the DSC Cooling Can

The DSC Cooling Can is a metal can that fitsover the DSC Cell. Coolant is placed in areservoir in the top of the can. An open-top belljar, an aluminum spacer, and a split O-ring areincluded with the accessory. To install thecooling can, follow these steps:

1. Remove the bell jar from the DSC Cell.Remove the original O-ring, and replace itwith the split O-ring shipped with the DSCCooling Can.

Figure 2.13Installing the DSCCooling Can

Aluminum Spacer

Split O-ring

Open-top Bell Jar

Cooling Can

DSC Cell

Installations for Subambient Operation



3. Place the aluminum spacer on top of the cellas shown in Figure 2.13.

4. Place the DSC Cooling Can over the DSCCell.

5. Place the open-top bell jar over the DSCCoolingCan.

When running subambient experiments, use a dry nitrogenpurge through the vacuum port (~100�150 mL/min) anda dry gas through the purge port to eliminate moisturebuild-up.

NOTE:


Starting the 2920 CE

1. Check all connections between the DSC2920 CE and the controller. Make sure eachcomponent is plugged into the correctconnector.

2. Press the instrument POWER switch to theON (1) position. The first screen to appearwill display the results of the internal confi-dence test, which is run each time you poweron the unit.

The HEATER and POWER indicator lamps may flickerunder low AC voltage conditions.

3. Watch the instrument display during theconfidence test for any error messages thatmay be indicated. If an error occurs, make anote of the test number in which the erroroccurred, and call TA Instruments forservice.

After the confidence test, the screen will brieflydisplay the system status, indicating the amountof data storage memory available and the GPIBaddress. Next follows the copyright display, thecell identification (if a cell is installed), and thenthe standby display, shown in Figure 2.14.

NOTE:

Starting the 2920 CE



Figure 2.14DSC 2920 CEStandby Display

Instruments should warm up for at least 30 minutesbefore performing expeirments.

4. Bring the instrument online with the TAcontroller.


NOTE:

Standby 23.25°C

HtFlow 0.012 mW


Shutting Downthe 2920 CE

Turning the system and its components on andoff frequently is discouraged. When you finishrunning an experiment on your instrument andwish to use the thermal analysis system for someother task, leave the instrument on; it will notinterfere with whatever else you wish to do.

If your system will not be used for longer thanfive days, we suggest that you turn it off. Topower down your instrument for any reason,simply press the POWER and HEATER switchesto the OFF (0) position.

Shutting Down the 2920 CE




CHAPTER 3: Running Experiments

Overview.....................................................3-3

Before You Begin .................................3-3

Calibrating the DSC ....................................3-4

Baseline Slope andOffset Calibration .................................3-5

Cell Constant Calibration .....................3-6

Temperature Calibration.......................3-7

Crosstalk Calibration ............................3-7

Running a DSC Experiment ........................3-8

Experimental Procedure ........................3-8

Preparing Samples ................................3-9

Determining Sample Size ...............3-9Physical Characteristics ...............3-10Selecting Sample Pans ..................3-11

Sample Pan Material .............3-11Sample Pan Configuration .....3-13

Nonhermetic Pans ...........3-13Hermetic Pans .................3-13Open Pans .......................3-14SFI Pans ..........................3-14

Encapsulating the Sample.............3-15Preparing NonhermeticSample Pans ..........................3-16Preparing HermeticSample Pans ..........................3-19

Running Experiments


Setting Up an Experiment .........................3-22

Setting Up Accessories .......................3-24

Loading the Sample ............................ 3-26

Starting an Experiment .......................3-28

Stopping an Experiment .....................3-28

Subambient Experiments ...........................3-29

DSC Cooling Can ...............................3-29

Applications.................................. 3-29Operation ...................................... 3-30

Quench-CoolingBetween Runs ........................ 3-30Starting a Run BelowAmbient Temperature ............ 3-31


OverviewThis chapter gives instructions on how to runexperiments with the DSC 2920 CE and both ofthe cell types:

• Differential Scanning Calorimeter (DSC)• Dual Sample Differential Scanning

Calorimeter (DSDSC)

To obtain accurate results, follow the procedurescarefully, and check the calibration periodically(e.g., once a week).

Only the instructions necessary for runningexperiments are given in this chapter; explana-tions of terminology and how the instrumentoperates are given in Chapter 4.

Before You Begin

Before you set up an experiment, ensure that thedesired cell, the DSC 2920 CE, and the TAcontroller have been installed properly. Makesure you have:

• Made all necessary cable connections fromthe DSC 2920 CE to the TA controller

• Connected all gas lines• Installed the desired cell onto the DSC 2920

CE (see Chapter 2)• Powered up each unit• Installed all appropriate options• Configured the instrument online with the

controller• Become familiar with controller operations• Calibrated the cell, if necessary (refer to the

following section on calibration).

Overview

Running Experiments


Calibrating the DSC

To obtain accurate experimental results youshould calibrate each standard DSC and dualsample DSC when you first install it. Thecalibration will be stored in the cell’s memoryand automatically entered when the cell isinstalled. Therefore, you can easily change cellson the 2920 CE without recalibrating each time.Once the initial calibrations are done, you cansave the resulting data files and reuse them whenneeded. For the best results, however, you shouldrecalibrate periodically.

Perform calibration runs that encompass thetemperature range you plan to use in yourexperiments. If you change the general tempera-ture range of your experiments later, you maywish to recalibrate within the new range.

For precise experimental results you will need togenerate a new calibration file whenever youchange one of the following parameters:

• Ramp rate (selected in the thermal method)• Purge gas• Cooling technique (LNCA, RCS, or DSC

Cooling Can)• First use of the cell.

However, an acceptable alternative is to use aprevious calibration, if the conditions are suffi-ciently similar to those of the experiments youplan to run. Calibration is performed in theinstrument’s calibration mode, which is accessedthrough the controller.


Calibration consists of several different types ofprocedures specific to each cell, which aredescribed briefly here. For more details onperforming each type of calibration, refer to theinstructions in the calibration program.

Baseline Slope andOffset Calibration

The baseline slope and offset calibration needs tobe performed separately for each cell. Thiscalibration involves heating an empty cellthrough the entire temperature range expected insubsequent experiments. The results may looksimilar to Figure 3.1 below. This figure showstwo example heat flow curves for an emptystandard DSC cell run from 25°C to 400°C.Ideally, the heat flow signal should be zero, sincethere is no sample in the cell, and it should haveminimum slope. The calibration program is usedto calculate the slope and offset values needed toflatten the baseline and zero the heat flow signal.

Figure 3.1Baseline SlopeCalibration

Calibrating the DSC

Running Experiments


Cell Constant Calibration

This calibration is based on a run in which acalibration material (e.g., indium) is heatedthrough its melting point. The calculated heat offusion is compared to the theoretical value. Thecell constant is the ratio between these twovalues. The onset slope, or thermal resistance, isa measure of the temperature rise of the samplethermocouple during a melt. In a perfect system,a calibration material melts at a constant tem-perature. However, in a system in which thethermocouple is not located in the sample, as thesample melts and draws more heat, a temperaturedifference develops between the sample and thesample thermocouple. The thermal resistancebetween these two points is calculated as theonset slope of the heat flow versus temperaturecurve on the front of the melting peak. The onsetvalue is used for kinetic and purity calculationsto correct for this thermal resistance.

In calibration of the DSDSC, the cell constantcalibration is performed in two experiments. Inthe first experiment the calibration material isplaced on sample side A, and sample side B isleft vacant. In the second experiment, thisarrangement is reversed, so that the standard isplaced on sample side B, and sample side A isleft vacant.


Temperature Calibration

Temperature calibration is based on a run inwhich a temperature calibration material (e.g.,indium) is heated through its melting point. Therecorded melting point of this material is com-pared to the known melting point, and thedifference is calculated for temperature calibra-tion. The same file used for the cell constantcalibration can be used for this calibration.

In addition, you can use up to four other calibra-tion materials to calibrate temperature. If you useone pair of known and observed points, the entirecurve is offset, or shifted, to the actual meltingpoint. If you use multiple materials, the tempera-ture is corrected by a cubic spline fit. Themultiple-point temperature calibration is moreaccurate than the one-point calibration.

Crosstalk Calibration

Crosstalk calibration is an additional calibrationprocedure that is necessary when the dual sampleDSC cell is used. This calibration uses the cellconstant data to calculate and eliminate anysignal cross-over occurring between the twosample sides of the dual sample DSC cell.

Calibrating the DSC

Running Experiments


Running aDSC Experiment

Experimental Procedure

All of your DSC experiments will have thefollowing general outline. In some cases, not allof these steps will be performed.

• Selecting and preparing a sample. Thisinvolves preparing a sample of theappropriate size and weight, selecting the pantype and material, and encapsulating thesample in the pan.

• Loading the sample pan (and a similarlyprepared empty reference pan) into the cell.

• Entering experiment information through theTA controller (sample and instrumentinformation).

• Creating and selecting the thermal method onthe controller.

• Attaching and setting up external accessoriesas required (e.g., purge gas, LNCA).

• Starting the experiment.


Preparing Samples

Determining Sample Size

Normally, sample weight in DSC experiments isin the range of 5 to 20 milligrams. If puritydeterminations are to be performed, sample sizesof 1 to 3 milligrams are recommended. Refer toTable 3.1 to guide you in selecting the samplesize and heating rates for your experiment.

Type of Sample SizeHeatingMeasurement (mg) Rate

(oC/min)

Glass transition 10 to 20 10 to 20

Melting point 2 to 10 5 to 10

Kinetics 5 to 10 5 to 20(Borchardt& Daniels)

Kinetics * 0.5 to 20(ASTM)

Heat capacity 10 to 70 20+

Purity 1 to 3 0.5 to 1

Crystallinity 5 to 10 5 to 10or oxidativestability

* Mass is inversely proportional to theheating rate. Use larger masses at slowerrates, smaller masses at higher rates.

+ Except for Modulated DSCTM, seeAppendix C.

Table 3.1DeterminingSample Size

Running a DSC Experiment

Running Experiments


Physical Characteristics

When making quantitative measurements orverifying reproducibility, it is important to ensuregood thermal contact between the sample andsample pan. The physical characteristics of thesample affect the quality of this contact.

When using powdered or granular samples,spread them evenly across the bottom of the panto minimize thermal gradients. For solid samples,select the side of your sample with the flattestsurface for contact with the pan. Afterencapsulating the sample, ensure that the panbottom is flat. If it is not, flatten the pan bottomby pressing it on a flat surface.

The contact between the pan and the raised sampleplatform on the constantan disc is as important as thecontact between the sample and sample pan.

NOTE:



Selecting Sample Pans

DSC samples must be in sample pans for analy-sis. Use the following guidelines to select asample pan material and configuration that meetthe temperature and pressure range, composition,and reactivity requirements of your experiment.

Sample Pan Material

Aluminum pans can be used in most experiments,unless the sample material reacts with aluminumor the temperature is expected to go beyond thatallowable for aluminum pans (600°C). Manyother sample pan materials are available forexperiments with special requirements. Forexample, you may wish to choose a particularpan material to improve the thermal conductanceto the sample. Sample pans made of platinum,copper, or gold are commonly used when thesample reacts with aluminum or has a transitionin the 600°C to 725oC region; sample pans madeof graphite are used when alloying or otherundesirable sample-pan interactions occur. Themany pan materials available enable you to studya wide variety of sample materials over thetemperature and pressure ranges of the standardand dual sample cells.

The maximum operating temperature for the DSC Cell is725oC (600oC in an oxidizing atmosphere). The maxi-mum operating temperature for the aluminum samplepans supplied with the cell is 600oC. To operate attemperatures above 600oC, use gold, platinum, copper,or graphite pans.


ttttt CAUTION:

ttttt CAUTION:

Running Experiments


Table 3.2 provides guidelines for one of the mostimportant factors in the selection of a sample panmetal: the temperature range you plan to use inthe experiment.

Table 3.2TA InstrumentsDSC Sample PanTemperature Ranges

Usable TemperatureSample Pan Range (°C)

Aluminum –180 to 600Copper –180 to 725Gold –180 to 725Platinum –180 to 725Graphite –180 to 725Aluminum (SFI)* –180 to 600Aluminum –180 to 600

(hermetic to300 kPa [3 atm]internal pressure)

Alodined aluminum –180 to 200(hermetic to300 kPa [3 atm]internal pressure)

Gold –180 to 725(hermetic to600 kPa [6 atm]internal pressure)

*SFI = solid fat index


Sample Pan Configuration

Once you have selected the sample pan materialto be used, you must determine the appropriatesample pan configuration. Depending on therequirements of the experiment, samples can becontained in:

• Nonhermetic pans• Hermetic pans• Open pans (sample pans without lids).

Nonhermetic Pans

Most samples can be run in nonhermeticallycrimped aluminum sample pans. These pansprovide better thermal contact between sample,pan, and constantan disc than open pans; reducethermal gradients in the sample; minimize samplespills; and enable you to retain the sample forfurther study.

Hermetic Pans

Hermetically sealed sample pans have the sameadvantages as the nonhermetic pans, plus theyhave an airtight seal that can resist higherinternal pressures (see Table 3.2). These pans areused for studies of: volatile liquids, materialsthat sublime, aqueous solutions above 100oC,and materials in a self-generated atmosphere.Because of its larger mass, a hermetic pan causesa slight loss of resolution compared with anonhermetic pan; however, only the system timeconstant is affected, not the calorimetricaccuracy.


Running Experiments


As a hermetically sealed sample is heated, theevolution of gaseous products causes the con-tainer pressure to increase. The sample containergradually deforms and may eventually leak. Thecontainer deformation does have some effect onthe baseline as the container area contacting theconstantan disc changes.

Avoid heating to temperatures that could cause thesample container to leak. Sample leakage could damagethe constantan disc. A hermetically sealed container canwithstand at least 300 kPa (3 atmospheres) of internalpressure. Some seals may contain higher pressures, andsuitable precautions should be taken. Gold pans canwithstand 600 kPa (6 atmospheres) of internalpressure.

Open Pans

Open pans (sample pans without lids) are usedwhen contact with the cell atmosphere or reactionof the sample with a gas is required. You canalso use hermetic pans as open pans by putting apinhole in the lid before sealing.

SFI Pans

SFI pans (so named because they were firstdeveloped for the solid fat index test) are idealfor waxy or oily substances. They contain aplatform on which the substance sits, whichprevents the substance from “wicking” up thesides of the pan. This design maintains a constantsurface area during the experiment, which isespecially important in oxidative studies, inwhich increased surface area could result infaster oxidation.

ttttt CAUTION:


Encapsulating the Sample

The Sample Encapsulating Press is used toseal both nonhermetic and hermetic sample pans.Refer to Table 3.3 as a general guidefor selectingthe encapsulating method for your experiment.

Table 3.3Selecting anEncapsulatingMethod

Sample Type MeasurementEncapsulatingPan

Solid Tg or Tm Nonhermetic,(nonvolatile) hermetic,

open

oxidative SFI or openstability

Cp Nonhermetic

Solid Cp Hermetic(volatile)

Liquid crystallization Hermetic,T

g or T

mSFI, or open

Cp Hermetic

oxidative SFI or open

Aqueous Cp, Tm, Tg Alodinedaluminumhermetic


Running Experiments


Preparing Nonhermetic Sample Pans

Before using the Sample Encapsulating Press,ensure that it is set up for nonhermetic crimping(see Appendix A).

Practice making a few nonhermetic sample pansto become familiar with this procedure beforeencapsulating your samples. If you have justchanged the die (from hermetic to nonhermetic),make a few sample pans to ensure that the diehas been installed properly.

1. If quantitative work will be done, weigh thesample pan and lid.

When doing quantitative work, use tweezers to handle thesample pan and lid. Touching them with your fingers couldleave residue that could affect your results.

2. Place the sample in the pan. If you are usinga powder or granular sample, spread itevenly in the pan.

3. Place a lid on the pan.

• If the sample is small or thin, powder, orgranular, align the lid with the pan (seeFigure 3.2).

• If the sample is large or bulky, invert thelid and place it in the pan.

Pans used with inverted lids should not be crimped.

NOTE:

NOTE:


Figure 3.2Placing the CoverOver the Pan

4. Place the sample pan in the well of the lowercrimping die.

5. Pull the Sample Press lever forward until thehandle hits the stop.

6. Raise the lever and remove the pan withtweezers.

Figure 3.3NonhermeticallySealed Sample


SAMPLEALIGNED COVER

PAN BEFORECRIMPING

PAN AFTERCRIMPING

Running Experiments


7. Inspect the pan. The bottom of the panshould be smooth, and the sides shouldappear rolled down. If there is a ridge on thebottom of the pan, loosen the lower dieholder thumbscrew, lower the bottom dieholder about ¼-turn by turning it clockwise,and repeat the process from step 4. Adjustthe bottom die holder until you obtain a flatpan bottom. Then, lock the bottom die holderin place by tightening the lower die holderthumbscrew.

Large or bulky samples may rupture the pan lid. If the lidruptures, lower the bottom die holder. Slight deformationof the lid is acceptable.

8. For quantitative work, weigh the crimpedsample pan and lid (containing the sample)and determine the sample weight by subtract-ing the weight of the empty sample pan andlid (step 1).

9. Prepare an empty nonhermetic pan and lid(follow steps 3 through 7) for use as thereference pan.

It is important that the same care be taken in preparingthe reference pan as in preparing the sample pan. The panbottom should be flat.

NOTE:

NOTE:


Preparing Hermetic Sample Pans

Before using the Sample Encapsulating Press,ensure that it is set up for hermetic crimping (seeAppendix C).

Practice making a few hermetic sample pans tobecome familiar with this procedure beforeencapsulating your samples. If you have justchanged the die (from nonhermetic to hermetic),make a few hermetic sample pans to ensure thatthe die has been installed properly.

To prepare a hermetic sample pan:

1. For quantitative work, weigh the sample panand lid.

When doing quantitative work, use tweezers to handle thesample pan and lid. Touching them with your fingers couldleave residue that could affect your results.

2. Carefully place the sample in the pan. Do notallow the sample to spill onto the lip of thepan. Place the hermetic lid on the pan, andplace the pan in the lower die in the SamplePress.

When using solid samples in hermetic pans forquantitative calorimetric measurements, invert the coverto improve sample�pan contact and minimize deadvolume. This is especially important for purity analyses.

NOTE:

NOTE:


Running Experiments


3. Place the flat side of the preforming toolagainst the upper die and hold it in place.With your other hand, pull the Sample Presslever forward until the preforming tool hitsthe stop.

4. Raise the lever and remove the preformingtool.

5. Lower the lever again with a steady motionuntil the handle hits the stop. Raise the leverand remove the pan with tweezers.

6. Inspect the pan. The bottom of the panshould be smooth. There should be a smooth,complete seal around the circumference ofthe pan (as opposed to the rolled downappearance of a nonhermetic pan), indicatinga tight seal.

7. For quantitative work, weigh the pan todetermine the sample weight.

8. Prepare an empty hermetic pan and lid foruse as the reference pan.

It is important that the same care be taken in preparingthe reference pan as in preparing the sample pan. The panbottom should be flat.

NOTE:


Figure 3.4HermeticallySealed Sample


Running Experiments


Setting Upan Experiment

Once you have prepared the sample, the next stepin your experiment is to enter the needed infor-mation in the TA controller. All of the controllerfunctions described in this section are accessedthrough the Instrument Control screen. Refer tothe Thermal SolutionsUser Reference Guide tolearn how to perform the following steps.

1. Select the Instrument.

2. Select the Instrument Mode.

3. Enter Sample Information.

4. Enter Instrument Information.

The instrument parameters that you set willbe stored in the cell’s memory and will beretrieved each time that the cell is used.

5. Create and Select Thermal Methods

The first time you use your DSC 2920 CEyou will need to create at least one thermalmethod to control experiments. Each methodis made of several segments, or individualinstructions (e.g., Equilibrate, Ramp), thatcontrol the state of the instrument.



For calorimetric measurements, start pro-gramming well below the onset temperatureof the transition you wish to measure. Thisallows time for the heating rate to stabilize atthe set rate and the sample and referenceplatforms to equilibrate. Allow at least 2minutes for temperature stabilization.

The maximum operating temperature for the DSC Cell is725oC (600oC in an oxidizingatmosphere). The maximum operatingtemperature for the aluminum sample pans suppliedwith the cell is 600oC. To operate at temperaturesabove 600oC, use gold, platinum, copper, or graphite(carbon) pans in a non-oxidizing atmosphere.


ttttt CAUTION:

ttttt CAUTION:

Running Experiments


Setting Up Accessories

If your experiment requires additional accesso-ries, such as a purge gas, RCS, or the LNCA,ensure that they are turned on, and make anynecessary adjustments before you start yourexperiment. Ensure that the system can achievethe temperatures in all segments of the method(e.g., if subambient temperatures are required,make sure your cooling device is properlyinstalled and filled). Use the following table as aguide in checking your DSC accessories.

Table 3.4DSC AccessoryAdjustments

ExternalEquipment Check or Adjustment

Air cool Ensure that the air supplyline valve from the airsource is open.

Ensure that the pressure isbetween 20 and 120 psi.

Purge gas Make sure the correct gasis connected to the 2920CE instrument.

Ensure that your supplyof purge gas is sufficientfor the needs of theexperiment.

Set the purge gas flowrate.

(table continued)



NOTE:

Table 3.4 (continued)

ExternalEquipment Check/Adjustment

LNCA Fill the LNCA tank withliquid nitrogen (see yourLNCA Operator’sManual).

Make sure the LNCA isconnected to the DSC2920 CE.

Turn on the LNCA.

Operation of the LNCA with theDSC 2920 CE is completelyautomatic as long as the powerto the LNCA is on.

Refrigerated Install the RCS CoolingCooling Head over the cell, andSystem turn on the RCS.

DSC Cooling Install the DSC CoolingCan Can over the cell, and

fill with the desiredcoolant.

Gas Switching Make sure the powerAccessory switch is on.

Make sure the necessarygas source(s) are properlyconnected.

Running Experiments


Loading the Sample

Once the sample pan has been prepared and thesample information has been recorded, you areready to load the sample pan into the DSC Cell.

If the cell has just been used, the bell jar and the compo-nents of the cell could be very hot. As a safe-operatingpractice, always use the tweezers to handle the cell coveror silver lid.

With the DSC Cell installed on the DSC 2920CE, load the sample pan into the cell as follows:

1. Remove the bell jar, cell cover, and silver lidfrom the cell.

2. Carefully place the sample pan(s) andreference inside the cell.

a. Single Sample Cell: Place the samplepan on the front, raised platform and thereference pan on the rear platform.Centering the pans within the grid willensure that they are centered on theplatforms (see Figure 3.5).

Figure 3.5DSC Standard CellPan Positions

NOTE:


b. Dual Sample Cell:Place the two samplesand an empty reference pan on the raisedplatforms shown in Figure 3.6. SampleA should be placed on the left platformand Sample B on the right. Be sure toplace the samples directly over theplatforms at an equal distance from oneanother.

Figure 3.6Loading Two Samples

3. Replace the silver lid, cell cover, and bell jar.


Running Experiments


!WARNING

Starting an Experiment

Before you start the experiment, ensure that theDSC 2920 CE is online with the controller andyou have entered all necessary experimentalparameters.

Tightening down the thumbscrews engages a powerinterlock in the instrument base. No power is suppliedto the cell without them. They must be in place to runthe instrument.

Start the experiment by pressing the START keyon the instrument keypad or Start on the DSCInstrument Control program. The instrument willrun your method to completion.

Stopping an Experiment

If for some reason you need to discontinue theexperiment, you can stop it at any point bypressing either the STOP key on the DSC 2920CE keypad or Stop on the DSC InstrumentControl program. Another function that stops theexperiment is Reject. However, the Rejectfunction discards all of the data from the experi-ment; the Stop function saves any data collectedup to the point at which the experiment wasstopped.

The REJECT function discards all experiment data.ttttt CAUTION:


SubambientExperiments

Subambient experiments can be performed withthe DSC 2920 CE using the Liquid NitrogenCooling Accessory (LNCA), the RefrigeratedCooling System (RCS), and the DSC CoolingCan. Please consult the manuals that come withthe LNCA and RCS for operation instructions.Instructions for operating the DSC Cooling Canare given below.

DSC Cooling Can

The DSC Cooling Can fits over the standard anddual sample DSC cells. Its function is to coolthe DSC cell more rapidly than the air coolfunction and to provide subambient operation.The reservoir is filled with coolant as needed toreach the desired temperature. An open-top belljar and a split O-ring are also included with theaccessory.

Installation instructions for the DSC CoolingCan are given in Chapter 2.

ApplicationsThe DSC Cooling Can is used:

• To quench-cool (rapid-cool) betweenanalyses. The DSC cell can be quench-cooled from 700°C to ambient in 3 minutes.

• To cool to a subambient temperature beforea thermal program is started.

Subambient Experiments

Running Experiments


OperationThis section contains the steps needed to use theDSC Cooling Can.

Quench-Cooling Between Runs

1. Carefully remove the DSC cell cover (it maybe hot). Place the DSC Cooling Can(without the insulation disc) over the cell.Pour in the coolant, typically liquid nitro-gen, using the open-top bell jar to minimizefrost build-up on the can and DSC cell.

Follow the safety procedures in the front of this manualwhen handling liquid nitrogen.

2. When the cell cools to ambient, remove theopen top bell jar and the DSC Cooling Can,and place the sample and reference in thecell.

3. Replace the DSC Cooling Can and open topbell jar, if you want to cool the sample andreference further.

4. Remove the Cooling Can when the desiredtemperature is reached.

5. Replace the cell cover and bell jar.

6. Start a temperature ramp without using theEquilibrate segment.

To prevent frost from forming or moisture from condens-ing on the constantan disc, do not remove the silver lidwhen the cell temperature is below ambient.

!WARNING

NOTE :


Starting a Run Below AmbientTemperature

1. Connect both the air cool and vacuum portsto one source of dry nitrogen using approxi-mately 150 cc/min flow.

2. Place the sample and reference in the cell atambient temperature and install the silverlid. Do not install the cell cover.

3. Place the DSC Cooling Can over the cell,and pour in the coolant using the open-topbell jar to minimize frost.

4. When the starting temperature is reached,remove the DSC Cooling Can and open topbell jar, then place the cell cover andstandard bell jar over the cell. Do notremove the silver lid.

5. Wait for the sample temperature to reach aminimum.

6. Start a temperature ramp without using theEquilibrate segment.

Subambient Experiments

Running Experiments



CHAPTER 4: Technical Reference

Description of the DSC 2920 CE ................ 4-3

DSC Standard and DualSample Cells ......................................... 4-4

Principles of Operation ............................... 4-6

Cell Block Heating ............................... 4-6

Sample and ReferenceThermocouples ..................................... 4-7

DSC Applications ........................................ 4-8

Sample Types ....................................... 4-8

Status Codes ............................................... 4-9

Guidelines for Quantitative Studies ...........4-13

Specific Heat Experiments .................4-13

Technical Reference



Description ofthe DSC 2920 CE

A complete DSC 2920 CE system consists ofthe instrument; a DSC, Dual Sample DSC, orPressure DSC cell; and a controller. Both thetemperatures and the heat exchanges associatedwith transitions in materials can be easily andrapidly measured by the system. The measure-ments provide quantitative and qualitative datarelative to physical or chemical changes of amaterial involving endothermic (heat absorption)or exothermic (heat evolution) processes.

The electrical connection formed between thecell and the DSC 2920 CE provides power to thecell, enables the instrument to recognize thecell type, and allows transmission of thermo-couple signals from the cell to the instrument.If a cell is not properly secured to the instrument,a spring-loaded interlock switch disconnectspower.

Description of the DSC 2920 CE

Technical Reference


DSC Standardand Dual Sample Cells

The standard and dual sample DSC cells (Figure4.1) both use a constantan (thermoelectric) discas a primary heat-transfer element. A silverheating block, capped with a vented silver lid,encloses the constantan disc. The selectedsample(s) and an inert reference are placed inpans that sit on raised portions of the disc. Heatis transferred through the constantan disc to boththe sample(s) and the reference pans. Differ-ential heat flow to the sample(s) and referenceare monitored by the CHROMEL®*-constantanarea thermocouples. The thermocouples areformed at the junctions of the constantan discand the CHROMEL® wafers welded to theunderside of the two raised portions of the disc.CHROMEL® and ALUMEL®* wires areconnected to the CHROMEL® wafers at thethermocouple junctions to measure sampletemperature. The ALUMEL® wire welded tothe reference wafer is for thermal balance.

Purge gas, entering the heating block through aninlet in the DSC cell’s base plate, is preheated toblock temperature by circulation before enteringthe sample chamber through the purge gas inlet.Gas exits through the vent hole in the silver lid.

Vacuum and air cooling ports on the DSC 2920CE lead to openings in the cell but not directly tothe sample chamber. A bell jar, placed over thecell and sealed with an O-ring, protects theoperator from evolved gases and permits cellevacuation.

* CHROMEL® and ALUMEL® are registeredtrademarks of Hoskins Manufacturing Company


Figure 4.1DSC Cell Cross-Section

Description of the DSC 2920 CE

MetalBell Jar

Technical Reference


Principlesof Operation

If a sample and an inert reference are heated ata known rate in a controlled environment, theincreases in sample and reference temperatureswill be about the same (depending on specificheat differences), unless a heat-related changetakes place in the sample. If this change takesplace, the sample temperature either evolves orabsorbs heat. In DSC, the temperature differ-ence between sample and reference from such aheat change is directly related to the differentialheat flow.

Cell Block Heating

The DSC 2920 CE controls the cell temperatureby heating a silver block with a resistive woundheater and monitoring its temperature with aclosely coupled control thermocouple. Theappropriate amount of power supplied to theheater is determined by the difference betweenthe temperature measured by the control thermo-couple and the set point temperature (thetemperature the system is attempting to reach).

Heat from the block then flows radially throughthe constantan disc toward the sample andreference platforms. The primary means of heattransfer to the sample and reference is throughthe disc, although some heat is transferredfrom the lid and walls of the cell through theatmosphere.

The DSC cell uses a Platinel II* control thermo-couple.

* Platinel II is a registered trademark of EnglehardIndustries.


Sample andReference Thermocouples

The thermocouples are connected in seriesopposition (back-to-back) so that if the sample(T

s) and reference (T

r) temperatures are the

same, the resulting electrical potential is zero. Ifthe sample temperature is higher than thereference, the output electrical potential is onepolarity; if the sample temperature is lower, thepolarity is reversed.

The DSC 2920 CE measures the differentialvoltage between the thermocouples at thesample and reference platforms. This voltage islinearized/converted to µW for the DSC by theE-curve.

The sample platform (the front platform) alsohas an ALUMEL®* lead wire forming aCHROMEL®*-ALUMEL® thermocouplejunction. The output from this thermocouple ismonitored on the T-axis after suitable coldjunction compensation.

Thus, the ∆q signal is determined byCHROMEL®-constantan thermocouples, andthe sample temperature is measured with aCHROMEL®-ALUMEL® thermocouple. TheDSC cell baseline is very reproducible, and thecell output can be compensated to obtain a levelbaseline over the cell temperature range with theDSC Calibration program.

* CHROMEL® and ALUMEL® are registeredtrademarks of Hoskins Manufacturing Company

Principles of Operation

Technical Reference


DSC Applications

The DSC can be applied to a broad range ofmaterials characterization, including thermaltransitions in polymers:

• Glass transitions, crystallization, and meltingtransitions

• Curing reactions and kinetics of thermosets• Oxidative stability of lubricants and polymers• Purity of pharmaceuticals and organics• Specific heat capacity of materials• Catalyst efficiency.

Sample TypesThe DSC 2920 CE can be used to analyzevirtually any material that can be put into a DSCsample pan. The most important consideration isthat the sample must make good thermal contactwith the pan. Samples of solids and liquids in anyof the following forms can be analyzed:

• Films• Fibers• Powders• Solutions• Composites.


Status Codes

Status codes are character strings that arecontinuously shown at the top left of the DSC2920 CE display. These codes tell you whatsegment in the method is currently being per-formed by the instrument.

Table 4.1Status Codes

Code Meaning

Air Cool The cell is being cooled byusing an Air Cool segmentor the Switch Air Coolfunction.

Autofill The LNCA is beingrefilled from a low-pressure bulk storagetank.

Calib The DSC 2920 CE isrunning in calibrationmode.

Cold The instrument heatercannot supply heat fastenough to keep up withthe thermal program. Thismay be caused by a largeballistic jump in theprogram, a faulty heater,or a faulty control thermo-couple signal.

(table continued)

Status Codes

Technical Reference


Table 4.1(continued)

Code Meaning

Complete The thermal method hasfinished.

Cooling The heater is cooling, asspecified by a Rampsegment.

Equilib The temperature is beingequilibrated to the desiredset point.

Err n An error has occurred.The instrument displaywill give the error codenumber (n, a two- orthree-digit code); thecontroller screen will alsoshow the complete errormessage and provide help.

Heating The heater temperature isincreasing, as specified bya Ramp segment.

Holding Thermal experimentconditions are holding; theprogram is suspended.Choose Start to continuethe run.

(table continued)



Code Meaning

Hot The temperature isbeyond the set point, andthe instrument cannotremove heat fast enoughto follow the thermalprogram. This is usuallycaused by a large ballisticjump to a lower tempera-ture or by a cooling rampbeing run without theLNCA.

Initial The temperature is beingequilibrated to the desiredset point. When thetemperature has reachedequilibrium, the status willchange to “Ready.”

Iso The thermal program isholding the currenttemperature isothermally.

Iso-track The instrument is holdingthe sample at a constanttemperature as specifiedby the Iso-track segment.

Jumping The heater is jumpingballistically to the set pointtemperature.

(table continued)

Status Codes

Technical Reference


Table 4.1Status Codes (cont'd)

Code Meaning

No Power No power is beingmeasured at the heater.Check the heater switchand cell hold-downscrews.

Ready The system has equili-brated at the initialtemperature and is readyto begin the next segment.Choose Start to continuethe method.

Reject The experiment has beenterminated and the dataerased.

Repeat The method is executing arepeat loop that does notinvolve temperaturecontrol segments.

Stand by The method and method-end operations arecomplete.

Temp oC The heater is in standbymode, and the experimenthas been terminated.

Temp * Temperature calibration isin effect. The heater is instandby mode, and theexperiment has beenterminated.


Guidelines forQuantitative Studies

You can obtain ∆H and specific heat data fromDSC experiments by following the procedures inthis section. You can also calculate specific heatusing the Modulated DSCTM option (refer toAppendix C for details).

Specific HeatExperiments

If you wish to calculate specific heat, followthese guidelines when running the sample:

1. Create a baseline profile:

a. Load the cell with empty sample andreference pans. Include lids if yourexperiment will use sealed pans, but donot crimp the sample pan (you will needto reuse it).

b. Create a method that holds isothermallyat the desired starting temperature for 5minutes, heats at the desired heat rate,and then holds at the limit temperaturefor 2 minutes.

c. Start the run. Deflection from the initialequilibrium point may be upward ordownward, depending on the specificheat difference between the sample andreference pans.

Guidelines for Quantitative Studies

Technical Reference


2. Repeat the run under identical conditionswith a weighed sample in the same samplepan used for the baseline profile. Do notadjust the baseline slope or perform a signalzero offset between the runs.

3. Plot the thermograms obtained with the dataanalysis program, using common limits andintervals in both plots.

4. Calculate the specific heat from the differ-ence between the sample and blank curvesat any desired temperature (see Figure 4.2).

Figure 4.2Specific Heatof Sapphire

∆∆∆∆∆H = 18.5 mW

Cp Hr m 60 ∆∆∆∆∆HE =

∆∆∆∆∆H = 23.5 mW


5. Substitute the difference into the followingequation:

60 E ∆H Hr m

where E = cell calibration coefficient at thetemperature of interest(dimensionless)

Hr = heating rate, in oC/minute

∆H = difference in y-axis deflectionbetween sample and blankcurves at the temperature ofinterest, in µW

m = sample mass, in mg

Cp = specific heat, in J/goC

The quantity 60E /Hr is constant under a givenset of experimental conditions. It converts the ymeasurement directly into units of specific heatin J/goC. For greatest accuracy, determine thevalue of this constant (as an entity) by running astandard material of known specific heat underconditions identical to those of the unknownsample. Then substitute the values of H, m, andCp for the standard into the above equation at thetemperature of interest.

A sapphire (Al2O3) standard is provided in theaccessory kit for this purpose. Table 4.2 (pages4-16 to 4-19) shows its respective specific heatvalues.

[ ]Cp =


Technical Reference


The values in the table were determined byGinnings and Furukawa of the National Bureauof Standards on aluminum oxide in the form ofsynthetic sapphire (corundum). The sapphirepieces passed a #10 sieve but were retained by a#40 sieve, and had 99.98 to 99.99 percent purityby weight. Specific heat values below theexperimental range were obtained by extrapola-tion of a Debye equation fitted to the ex-perimental value at the lowest temperature.

Table 4.2Aluminum OxideSpecific Heat*

Cp °C K J/g°C

–183.15 90 0.0949–173.15 100 0.1261–163.15 110 0.1603–153.15 120 0.1968–143.15 130 0.2349–133.15 140 0.2739–123.15 150 0.3134–113.15 160 0.3526–103.15 170 0.3913 –93.15 180 0.4291 –83.15 190 0.4659 –73.15 200 0.5014 –63.15 210 0.5356 –53.15 220 0.5684

* Taken from D.A. Ditmars, et al, J.Res. Nat. Bur. Stand., Vol 87, No.2, pages 159–163 (1982). This is apublic domain publication.

(table continued)


Table 4.2(continued)*

°C K J/g°C

–43.15 230 0.5996–33.15 240 0.6294–23.15 250 0.6579–13.15 260 0.6848 –3.15 270 0.7103 0.00 273.15 0.7180 6.85 280 0.7343 16.85 290 0.7572 26.85 300 0.7788 36.85 310 0.7994 46.85 320 0.8188 56.85 330 0.8373 66.85 340 0.8548 76.85 350 0.8713 86.85 360 0.8871 96.85 370 0.9020106.85 380 0.9161116.85 390 0.9296126.85 400 0.9423136.85 410 0.9545146.85 420 0.9660156.85 430 0.9770166.85 440 0.9875176.85 450 0.9975186.85 460 1.0070196.85 470 1.0161206.85 480 1.0247216.85 490 1.0330

* Taken from D.A. Ditmars, et al, J.Res. Nat. Bur. Stand., Vol 87, No.2,pages 159–163 (1982). This is apublic domain publication.

(table continued)


Cp

Technical Reference


Table 4.2Aluminum Oxide SpecificHeat (cont'd)*

°C K J/g°C

226.85 500 1.0409236.85 510 1.0484246.85 520 1.0557256.85 530 1.0627266.85 540 1.0692276.85 550 1.0756286.85 560 1.0817296.85 570 1.0876306.85 580 1.0932316.85 590 1.0987326.85 600 1.1038336.85 610 1.1089346.85 620 1.1137356.85 630 1.1183366.85 640 1.1228376.85 650 1.1271386.85 660 1.1313396.85 670 1.1353406.85 680 1.1393416.85 690 1.1431426.85 700 1.1467446.85 720 1.1538466.85 740 1.1604486.85 760 1.1667506.85 780 1.1726526.85 800 1.1783546.85 820 1.1837566.85 840 1.1888

* Taken from D.A. Ditmars, et.als., J.Res. Nat. Bur. Stand., Vol 87, No.2, pages 159–163 (1982). This is apublic domain publication.

(table continued)

Cp


Table 4.2(continued)*

°C K J/g°C

586.85 860 1.1937606.85 880 1.1985626.85 900 1.2030646.85 920 1.2074666.85 940 1.2117686.85 960 1.2159706.85 980 1.2198726.85 1000 1.2237746.85 1020 1.2275766.85 1040 1.2312786.85 1060 1.2348806.85 1080 1.2383826.85 1100 1.2417846.85 1120 1.2451866.85 1140 1.2484886.85 1160 1.2516906.85 1180 1.2548926.85 1200 1.2578976.85 1250 1.26531026.85 1300 1.27241076.85 1350 1.27921126.85 1400 1.28561176.85 1450 1.29171226.85 1500 1.29751276.85 1550 1.30281326.85 1600 1.30791376.85 1650 1.3128

* Taken from D.A. Ditmars, et al, J.Res. Nat. Bur. Stand., Vol 87, No.2,pages 159–163 (1982). This is apublic domain publication.


Cp

Cp

Technical Reference


TA Instruments DSC 2920 CE 5–1

CHAPTER 5: Maintenanceand Diagnostics

Overview ....................................................5-3

Routine Maintenance ..................................5-4

Inspection .............................................5-4

Cleaning the Instrument .......................5-4

Cleaning a Contaminated Cell ..............5-5

Cleaning DSC Pans ..............................5-6

Sample Encapsulating Press.................5-7

Diagnosing Power Problems .......................5-8

Fuses ....................................................5-8

Furnace Power Check .....................5-9

Heater Indicator Light ........................ 5-10

Power Failures ................................... 5-11

DSC 2920 CE Test Functions ................... 5-12

The Confidence Test .......................... 5-12

Replacement Parts .................................... 5-15

Maintenance and Diagnostics

5–2 TA Instruments DSC 2920 CE


OverviewThe procedures described in this section are thecustomer�s responsibility. Any further main-tenance should be performed by a representativeof TA Instruments or other qualified servicepersonnel.

Because of the high voltages in this instru-ment, untrained personnel must not attemptto test or repair any electrical circuits.

!WARNING

Overview



RoutineMaintenance

InspectionExamine the instrument periodically for goodcondition as follows:

� Ensure that the furnace area is clean. Anysample spillage or residue should be removedbefore the next experiment.

� Keep the cell connector on the DSC 2920CE free of dust, debris, and moisture.

Cleaningthe Instrument

You can clean the DSC 2920 CE keypad asoften as you like. The keypad is covered with asilk-screened Mylar* overlay that is reasonablywater resistant but not waterproof or resistant tostrong solvents or abrasives.

A household liquid glass cleaner and a papertowel are best for cleaning the instrumentkeypad. Wet the towel, not the keypad, with theglass cleaner, and then wipe off the keypad anddisplay.

* Mylar is a registered trademark of theDu Pont Company.


Cleaning aContaminated Cell

A poor baseline is often the sign of a contami-nated cell. DSC cells must be cleaned properlyto maintain satisfactory operation. Scraping thecontamination off is not recommended, becausethe constantan disc is very thin (about 0.1 mm, or0.004 inches), and if the disc deforms, thebaseline may be affected. Scraping can causesevere damage to the cell if it is not donecarefully.

If your baseline performance begins to deterio-rate, try the following recommended cleaningprocedure.

� Begin cleaning by heating the cell with an airpurge to 50°C above the highest operatingtemperature or 600°C, whichever is lower,without pans or bell jar. Use a heating rateof 20°C per minute.

� After cool-down, lightly brush out the cellwith a small fiberglass eraser (included in theDSC accessory kit).

� Run the method again and compare thebaselines. If there is a marked improvementbut the baseline is still unacceptable, thecontaminant probably oxidized and reducedto an inert ash. Run the method again andcheck for further improvement.

� Once the baseline is acceptable, return tonormal operation.

If the constantan disc looks clean and is not bentor cracked, but the baseline problem remains, itis probably not due to contamination; the cellmay need to be replaced (contact your TAInstruments service representative).

Routine Maintenance



Cleaning DSC Pans

The aluminum, gold, and copper pans and thehigh pressure capsules provided for use with TAInstruments DSC systems are manufactured tohigh quality standards, including cleaning toremove contaminants that might be present fromthe manufacturing process. For most applica-tions, these pans can be used as received;however, if the pans are used for high sensitivityexperiments (e.g., oxidative stability), an addi-tional cleaning process is recommended beforeuse. This procedure is taken from Appendix Aof ASTM standard E1858 Test Method forOxidative Induction Time of Hydrocarbons byDifferential Scanning Calorimeters.

Follow the steps below to clean the TA Instru-ments DSC sample pans:

1. Place 200 pans in a 250 mL Erlenmeyerflask that has been fitted with a glassstopper.

2. Add approximately 150 mL of reagent gradexylene (enough to cover the pans).

3. Swirl the flask, containing the pans andxylene, for 0.5 to 2.0 min.

4. Let the flask stand for 1.0 min.

5. Decant the xylene out of the flask.

6. Repeat steps 1 through 5.

7. Add approximately 150 mL of reagent gradeacetone after the second xylene wash.


8. Swirl the flask, containing the pans andacetone, for 0.5 to 2.0 min.

9. Let the flask stand for 1.0 min.

10. Decant the acetone out of the flask.

11. Repeat steps 7 through 10.

12. Rotate the flask�so that no pans adhere tothe bottom or side of the flask�as you flownitrogen at 150 to 200 mL/min over the wetpans to drive off the excess solvent. Thisshould take approximately 5 to 6 min.

13. Return the cleaned pans to their storagecontainer and record the date they werecleaned.

SampleEncapsulating Press

The only maintenance needed for the SampleEncapsulating Press is an occasional drop of lightmachine oil on the cam. Also, make sure the diesare free of material that could scratch theirsurfaces and impair the seal.

Routine Maintenance



Diagnosing Power Problems

FusesThe DSC 2920 CE contains several internalfuses; however, they are not user serviceable. Ifany of the internal fuses blows, a hazard mayexist. Call your TA Instruments service repre-sentative.

The only fuses that you should service yourselfare the external fuses, located on theinstrument�s rear panel. Both are housed insafety-approved fuse carriers, labeled F1 and F2(see Figure 5.1). Replace these fuses with thesame type and rating only.

Figure 5.1Fuse Locations

Always unplug the instrument before youexamine or replace the fuses.

Fuse 1 Fuse 2

!WARNING


Fuse F1 is in the circuit between the POWERswitch and the instrument control circuits. Allpower for internal operations and instrumentfunctions, except heater power, passes throughthis fuse. If this fuse blows, you will get noresponse from the instrument when you attemptto turn it on.

Fuse F2 is in the circuit between the mainelectrical input and the POWER switch. Thisfuse protects all internal components, includingthe furnace. If this fuse blows, you will get noresponse from the instrument when you attemptto turn it on.

Furnace Power Check

Furnace power is always checked at the begin-ning of a method. Power supplied to the furnaceis switched by a computer-controlled relay aswell as by the HEATER switch located on theinstrument�s front panel. The HEATER switchmust be ON (1) to start a method.

The light in the HEATER switch will glow onlyafter an experiment is initiated.The heaterswitch will continue to glow, even if it isswitched to the OFF (0) position, until the ''StandBy'' status code is displayed.

NOTE:




HeaterIndicator Light

The indicator light in the HEATER switch on thefront panel of the DSC 2920 CE glows when-ever the power control circuitry is enabled. If thelight does not come on when the method isstarted, the indicator light may be defective or ahardware problem may exist in the DSC 2920CE (call your TA Instruments Service Represen-tative).

The heater light may also remain on after amethod has terminated. This can happen underthe following two conditions:

1. If the DSC 2920 CE is configured for autosampling and the cell furnace is beingactively returned to the load temperaturewindow after the completion of a method.

2. If the method-end condition �Return totemperature range� function is chosen; seethe Thermal SolutionsUser ReferenceGuide for further details.

Pressing the instrument STOP key after thecompletion of a method manually overrides thepost-experiment heater power conditions.

� If an LNCA is connected to the DSC 2920CE, STOP terminates any active autofilloperation and also turns off the heatexchanger jacket heater.

� If the instrument has an Autosampler andthe cell temperature is actively returning tothe load window, two depressions of theSTOP key may be required. The firstdepression aborts the return to thetemperature load window. The seconddepression disables any active LNCAfunctions.


PowerFailures

A power failure caused by a temporary drop inline voltage results in one of two responses bythe DSC 2920 CE:

� If the drop is fairly large and of long duration(20 milliseconds or more), the system willreset and go into its power-up sequencewhen power resumes.

� If the drop is small or of short duration, thesystem may halt, and you may see �ERRF02� on the display. This message meansthat the system has detected a power failureand has shut down. The instrument will notrestart until reset. To reset, press the Resetbutton on the DSC 2920 CE back panel.

If �ERR F02� appears at startup and remainseven after you have tried to restart the instru-ment, the detection circuitry itself is probably atfault. Do not try to repair it yourself; call yourTA Instruments service representative.

The DSC 2920 CE is designed for a nominal linevoltage of 120 volts AC (± 10%), 50 or 60 Hz. Itshould not be operated outside this range. Lowline voltage may result in poor instrumentoperation; high line voltage may damage theinstrument.




DSC 2920 CE Test Functions

The DSC 2920 CE has three levels of test anddiagnostic functions:

� The confidence test that is run every timethe instrument is started.

� Cycling test functions that continuously testspecific functions.

� A manufacturing verifier test mode thatcoordinates and logs the results of a se-quence of confidence tests and drift runs.

These test functions are always present in theinstrument. They are designed to aid manufac-turing and service personnel in checking andrepairing the instrument.

The Confidence Test

The DSC 2920 CE confidence test is run eachtime the instrument is turned on or reset. Theconfidence test checks most of the computer andinterface components in the system.

When the confidence test is running, the numberof the test currently being performed is shown onthe display. The test number appears as a two-digit hex number on the lower right of thedisplay. This number is changed as each newtest is started. Most of the tests are very brief,so their test numbers may not be apparent.


The length of time required to run the confidencetest depends on the options installed. A standardDSC 2920 CE system takes about 4 seconds.The longest tests are the DRAM tests, whichtake about 2 seconds.

After the tests are completed, a series of sign-onmessages are displayed. The system then startsrunning, and the Ready light on the back of theinstrument glows. If a cell is plugged into theinstrument, the cell type is read and displayed.

If an error is detected, an error message isposted on the bottom line of the display. Nonfatalerrors are displayed for 3 seconds, and then theconfidence test continues. A fatal error occurswhen a circuit essential to the operation of theinstrument has failed the confidence test; theinstrument cannot reliably perform any furtherfunctions. The system stops when the fatal erroris posted, and the ready light remains off.

Table 5.1 summarizes the primary confidencetests and the error codes for the DSC 2920 CE.If any errors occur during the confidence test,call your TA Instruments service representative.

DSC 2920 CE Test Functions



Table 5.1DSC 2920 CEConfidence Test

Test Area Being TestedNumber

� CPU logic30 CMOS RAM4n Program memory5n CPU board I/O functions6n DRAM data storage

memory70 GPIB test82 Keypad testAn Analog board testsBn Interface board testsD0 Saved memory checksum


Replacement PartsTable 5.2List of DSC2920 CE Parts

Part Number Description

900660.903 1 DSC accessory kit815401.901 1 DSC Standard Cell, new

replacement815201.901 1 DSC Dual Sample Cell,

new replacement910824.001 1 DSC cleaning brush900639.901 1 DSC cover915033.901 1 DSC hold-down shoul-

der thumbscrew withretainer ring

815008.001 1 DSC operator�s manual205220.021 1 fuse, 1.25 amp ceramic205220.041 1 fuse, 12.00 amp900682.001 1 O-ring, Silicon, split for

DSC Cooling Can900786.901 200 pan bottoms, alumi-

num crimp900779.901 200 pan covers, aluminum

crimp900635.000 1 silver lid for DSC, flat

with hole259538.000 1 stainless steel needle-

point tweezer202515.000 1 standard, sapphire

specific heat

(table continued)

Replacement Parts





900902.901 1 standard, vial of indiummetal

008837.001 1 gas ring lapping tool281050.001 1 O-ring for pneumatic

connections270726.001 Conductive O-ring815025.001 Metal bell enclosure

TA INSTRUMENTS DSC 2920 CE A�1

The Sample Encapsulating Press

Appendix A: The Sample EncapsulatingPress

Introduction

The Sample Encapsulating Press is used to sealsamples in hermetic and nonhermetic samplepans. Two dies come with the press: one forhermetic sealing and one for nonhermetic sealing.This appendix explains how to change these dies.

Instructions for sealing samples with the SampleEncapsulating Press are given in Chapter 3 ofthis manual.

Figure A.1Sample Encapsulating PressWith Nonhermetic Dies Installed

Appendix A

A�2 TA INSTRUMENTS DSC 2920 CE

Setting Up the Pressfor Nonhermetic Sealing

The Sample Encapsulating Press is shipped withthe upper nonhermetic die installed. To set upthe press to make nonhermetic sample pans(when the die is set up for hermetic pans),proceed as follows:

l. Remove the hermetic die set:

a. Loosen the thumbscrew on the column ofthe Sample Press (see Figure A.1).

b. Lower the lower die holder by turningthe base screw on the bottom of the presscounterclockwise.

Figure A.2Lowering the Base Screw

c. Lift the lower hermetic die and remove itfrom the die holder.



2. Place the lower nonhermetic die (Figure A.3)into the lower die holder (large end up).

Figure A.3The Nonhermetic Dies

3. Place the upper nonhermetic die around theplunger of the upper hermetic die (visiblewhen the lever is lowered).

4. Push the upper nonhermetic die upwardagainst the spring-loaded plunger and lock itin place by tightening the setscrew (FigureA.4) with a 0.050" hex wrench.

SETSCREW

Appendix A


Figure A.4Lower Die Setscrew

5. Adjust the height of the upper and lowerdies:

a. Pull the Sample Press lever all the waydown (until it rests on the column).

b. Turn the screw on the underside of thepress clockwise as far as it will go.Then turn the screw back about ¼ turnand tighten the lower die holder thumb-screw to lock the lower die holder inplace. When the press is adjustedproperly, the upper and lower dies justtouch. The height of the bottom die mayneed adjusting based on the sampleheight.

LOWER DIESETSCREW



c. Make a few sample pans (see Chapter 3)to check the die setting. A good nonher-metic pan will have a flat bottom, andthe sides of the pan will appear rolleddown (see Table A.1).

Table A.1Specifications for Nonhermetic Pans

Uniform foldingof lid aroundcircumference

Flat surfaceon the bottomof the pan; noridge aroundcircumference

No visible gapsbetweenlid and pan

Appendix A


Setting Upthe Press forHermetic Pans

l. Remove the nonhermetic die set:

a. Lower the lever until you can see thesetscrew on the upper nonhermetic die.If necessary, turn the upper die to accessthe lower die setscrew. Loosen thesetscrew (Figure A.4) with a 0.050" hexwrench, raise the lever, and remove theupper die.

b. Loosen the thumbscrew on the column ofthe Sample Press (see Figure A.1).

c. Lift the lower nonhermetic die andremove it from the die holder.

2. Place the lower hermetic die (Figure A.5)into the lower die holder, either end up.

Figure A.5The Hermetic Dies



3. Check the spring tension of the upperhermetic die (this is the die that remains inthe press when the nonhermetic die is re-moved) by pushing up on the center plunger.If the plunger does not move, adjust thespring tension as follows:

a. Lower the Sample Press lever. Raise thelower die holder until it contacts theupper die holder, then unscrew the holder¼ turn. (Loosen the thumb-screw beforeunscrewing the lower dieholder.)

b. Keep the lever down and unscrew theupper die setscrew, letting the die comein contact with the lower die. (Theupper die is spring loaded and will snapdown to contact the lower die.)

c. Tighten the setscrew on the upper die.

d. Check the tension again. Continue toadjust until you can move the upper dieplunger.

4. Adjust the setting of the upper and lowerdies:

a. Pull the lever down all the way (until itrests on the column).

b. Turn the screw on the underside of thepress clockwise as far as it will go.Then turn the screw back about ¼-turnand tighten the lower die holder thumb-screw to lock the lower die holder inplace.

Appendix A


c. Make a few sample pans to check the diesetting (see Chapter 3 for instructions).A good hermetic pan will have a flatbottom, with a complete seal around thecircumference of the pan, and the sidesof the pan will appear flat and smooth(see Figure A.6).

Figure A.6Properly SealedHermetic Pan

TA Instruments DSC 2920 CE B�1

Appendix B: Ordering Information

United States:TA Instruments, Inc.109 Lukens DriveNew Castle, DE 19720Telephone: (302) 427-4000 or (302) 427-4040Fax: (302) 427-4001

HELPLINE—U.S.A.For technical assistance with current orpotential thermal analysis applications,please call the Thermal Analysis Help Deskat (302) 427-4070.

SERVICE—U.S.A.For instrument service and repairs,please call (302) 427-4050.

TA Instruments Ltd.Europe HouseBilton CentreCleeve RoadLeatherhead, Surrey KT22 7UQEnglandTelephone: 44-1-372-360363Fax: 44-1-372-360135

TA Instruments GmbHSiemenstrasse 163755 AlzenauGermanyTelephone: 49-6023-30044Fax: 49-6023-30823

(continued on next page)

Appendix B

B�2 TA Instruments DSC 2920 CE

TA Instruments BeneluxOttergemsesteenweg 461B-9000 GentBelgiumTelephone: 32-9-220-79-89Fax: 32-9-220-8321

TA Instruments JapanNo. 5 Koike Bldg.1-3-12 KitashinagawaShinagawa-Ku, Tokyo 140JapanTelephone: 813/3450-0981Fax: 813/3450-1322

TA Instruments FranceB.P. 60878056 Saint-Quentin-YvelinesCedexFranceTelephone: 33.1.30.48.94.60Fax: 33.1.30.48.94.51

TA Instruments SpainWaters Cromatografía, S.A.División TA InstrumentsAvda. Europa, 21. Pta. Baja28108 AlcobendasMadrid, SpainTelephone: 34-91-661 8448Fax: 34-91-661 0855

Printed in U.S.A.

TA INSTRUMENTS DSC 2920 CE C�1

Modulated DSCTM Option

Appendix C: ModulatedDSCTM Option

Introduction to Modulated DSC ..................C-5

Option Installation .......................................C-7

Choosing When to UseMDSC vs. DSC ..........................................C-8

Background...........................................C-8

Limitations of Traditional DSC ............C-8

Analysis of ComplexTransitions .....................................C-9Need for IncreasedSensitivity.....................................C-10Need for IncreasedResolution....................................C-10

Principles of Operation .............................C-12

Overview ............................................C-12

Signal Deconvolution ................................C-17

How Signals are Generated ................C-17

Visual Interpretation ofModulated Heat Flow .........................C-18

Obtaining Multiple Heating RateInformation.........................................C-20

Appendix C

C�2 TA INSTRUMENTS DSC 2920 CE

Using MDSC.............................................C-22

Selecting MDSC Modeand Signals .........................................C-22

The Modulate Segment .......................C-27

Selecting ModulationAmplitude.....................................C-29Selecting ModulationPeriod...........................................C-22

Signal Time Delays ...............C-33Selecting Heating Rate .................C-33

Special Considerations in CreatingMDSC Methods ..................................C-34

Ramp Start Temperature..............C-34Ramp Final Temperature .............C-36

Isothermal MDSC...............................C-36

Cooling...............................................C-37

Cooling Devices ...........................C-37Sine Wave Distortion ...................C-38

Signal Control.....................................C-39

Sampling Interval (Data Rate) ............C-40

Calibrating with MDSC ............................C-41

DSC Calibration. ................................C-41

Proceudre for Measuring MDSCHeat Capacity CalibrationConstant [K(Cp)*] ..............................C-41

TA INSTRUMENTS DSC 2920 CE C�3


Calibrant ......................................C-42Modulation Conditions .................C-42Temperature of Measurement ......C-42Calibration and MeasurementProcedure .....................................C-42

Measuring Heat Capacity ...................C-52

Guidelines for RunningMDSC Experiments ..................................C-54

Background.........................................C-54

General SamplePreparation .........................................C-55

General MDSC OperatingParameters ..........................................C-56

Example MDSC Experiment ..............C-59

Experimental Conditions ..............C-59Observations ................................C-61

Applications ..............................................C-64

Separation of OverlappingReversing and NonreversingThermal Transitions ...........................C-62

Increased Sensitivity forDetection of Glass Transitions ...........C-65

Direct Measurement ofHeat Capacity .....................................C-67

Isothermal Cure Evaluation ................C-68

Direct Measurement ofThermal Conductivity .........................C-69

Appendix C

C�4 TA INSTRUMENTS DSC 2920 CE

Specific MDSC OperatingParameters for DifferentTransitions or Properties ...........................C-71

Glass Transitions ................................C-71

Polymer Melting (IntialCrystallinity) .......................................C-72

Nonreversing Transitions....................C-74

Heat Capacity &Thermal Conductivity .........................C-74

TA INSTRUMENTS DSC 2920 CE C–5


Introduction toModulated DSCTM *

This appendix describes how to use the Modu-lated DSC (MDSC) option for the DSC 2910and DSC 2920 CE.

MDSC is used to study the same materialproperties as conventional DSC including:transition temperatures, melting and crystalliza-tion, and heat capacity. However, MDSC alsoprovides unique capabilities that increase theamount of information that can be obtained froma single DSC experiment, thereby improving thequality of interpretation. These capabilitiesinclude:

� Measurement of heat capacity and heat flowin a single experiment

� Separation of complex transitions into moreeasily interpreted components

� Increased sensitivity for detection of weaktransitions

� Increased resolution of transitions withoutloss of sensitivity

� Increased accuracy in the measurement ofpolymer crystallinity

� Direct determination of thermal conductivity.

* Modulated DSCTM and MDSCTM are terms whichdescribe proprietary technology invented by Dr.Mike Reading of ICI Paints (Slough UK) andpatented by TA Instruments (U.S. Patent Nos. B15,224,775; 5,248,199; 5,335,993; 5,346,306).

Appendix C

C–6 TA INSTRUMENTS DSC 2920 CE

The MDSC� option includes special enhance-ments to the TA controller software and theDSC 2910 and DSC 2920 CE software.

Although MDSC experiments can be performedwith compressed air, optimum performance ofthe MDSC experiment often requires the use ofeither the Refrigerated Cooling System (RCS) orthe Liquid Nitrogen Cooling Accessory (LNCA).



Option InstallationThe Modulated DSC option is field installable byqualified service personnel (see separate installa-tion procedure included with the MDSCTM kit).The following are required:

� Version 1.0 or higher DSC 2920 CE or 2910Software (included in kit)

� Compatible version of controller operatingsoftware

� MDSC software option key (included in kit)

Installation of the LNCA Heat Exchanger andRefrigerated Cooling System (RCS) are coveredin their respective manuals.

A DSC instrument with MDSC capabilityproperly installed can be identified by the�MDSC Installed� message on the instrumentdisplay screen following the confidence test, andby the letters �MDSC� in the instrument identifi-cation string on the configuration screen of thecontroller (e.g., �2920 CE MDSC V1.0A�).

The MDSC option is not compatible withthe DSC 910, the DSDSC 912, the DSC 10instrument, the 1090 controller, or the9900 controller.

Appendix C


Choosing When toUse MDSCTM vs. DSC

Background

Traditional DSC is a well-accepted technique foranalyzing thermal transitions in materials. Itprovides information on the temperature at whichtransitions occur as well as quantitative measure-ment of the heat associated with the event.MDSC is an extension of DSC that provides thesame information as DSC plus new informationthat permits unique insight into the structure andbehavior of materials.

The need for extending the capabilities oftraditional DSC, via MDSC, is obvious from areview of the limitations of traditional DSC.MDSC overcomes all of these limitations and istherefore the technique of choice when they areobserved in traditional DSC experiments.

Limitations ofTraditional DSC

Problems associated with DSC measurementsfall into three general categories. In order ofimportance these are: analysis of complextransitions; need for increased sensitivity; andneed for increased resolution.



Analysis ofComplex Transitions

Most transitions are complex due to the fact thatthey involve multiple processes. Exampleswould include the enthalpic relaxation that occursat the glass transition, and crystallization ofamorphous or metastable crystalline structuresprior to or during melting. Enthalpic relaxation isan endothermic process that can vary in magni-tude depending on the thermal history of thematerial. Under some circumstances it canmake the glass transition appear to be a meltingtransition. Simultaneous crystallization andmelting make it nearly impossible to determinethe real crystallinity of the sample prior to theDSC experiment. These problems are com-pounded further when analyzing blends ofmaterials.

This significant limitation in traditional DSC isdue to the fact that DSC measures only the sumof all thermal events in the sample. Whenmultiple transitions occur in the same tempera-ture range, results are often confusing andmisinterpreted. MDSC� eliminates this prob-lem by separating the total heat flow signal intoits heat capacity and kinetic components. This isdiscussed later in this appendix.

Appendix C


Need for IncreasedSensitivity

The ability of DSC to detect weak transitions isdependent on both short-term (seconds) noise inthe heat flow signal and long-term (minutes)variations in the shape of the heat flow baseline.However, since short-term noise can be effec-tively eliminated by signal averaging, the reallimitation for reproducibly detecting weaktransitions is variation in baseline linearity.Because of the need to use different materials inthe construction of DSC cells and because ofchanges in the thermal properties of thesematerials and the purge gas, all commercial DSCinstruments have varying degrees of baselinecamber.

MDSC eliminates this problem by using the ratioof two signals to calculate real changes in thesample heat capacity rather than just the abso-lute value of the heat flow signal. This is furtherillustrated in the section on Principles of Opera-tion.

Need for Increased Resolution

High resolution, or the ability to separate transi-tions that are only a few degrees apart requiresthe use of small samples and low heating rates.However, the size of the heat flow signaldecreases with reduced sample size and heatingrate. This means that any improvement inresolution results in a reduction in sensitivity andvice versa. DSC results are always a compro-mise between sensitivity and resolution.



MDSC� solves this problem by having effec-tively two heating rates. The average heatingrate can be as low as needed to achieve thedesired resolution while the instantaneousheating rate can be as high as needed to createa large heat flow signal.

Appendix C



Overview

The schematic diagram for the 2920 CE heatflux DSC cell is shown in Figure C.1. Thesample and a reference sit on raised platformsformed in the thermoelectric (constantan) disk,which serves as the primary means of heattransfer from the temperature programmedfurnace.

Figure C.1Heat FluxDSC Schematic

Traditionally, the temperature of the furnace israised or lowered in a linear fashion, and theresultant differential heat flow to the sample andreference is monitored by area thermocouplesfixed to the underside of the disk platforms.



These thermocouples are connected in seriesand measure the differential heat flow using thethermal equivalent of Ohm�s Law:

dQ = ∆Tdt RD

where: dQ/dt = heat flow∆T = temperature difference between

reference and sampleRD = thermal resistance of constantan

disc

In Modulated DSC�, the same heat flux DSCcell is used, but a sinusoidal temperature oscilla-tion (modulation) is overlaid on the conventionallinear temperature ramp, (Figure C.2). Theresulting heating rate is sometimes faster thanthe underlying linear heating rate, and sometimesslower than the underlying rate, (Figure C.3).The actual variations in heating rate depend onthree experimental variables. They are theunderlying heating rate, the amplitude of modula-tion, and the period (frequency) of modulation.

Figure C.2Oscillation Overlaid

Appendix C


Figure C.3Resulting Heating Rate

To appreciate the impact those variables canhave on the heat flow results obtained, thegeneral equation describing calorimetric responseneeds to be examined. One way to mathemati-cally represent DSC heat flow is:

dQ/dt = Cp (dT/dt) + f(t,T)

where: dQ/dt = heat flowdT/dt = heating rateCp = sample heat capacityt = timef(t,T) = function of time and

temperature whichgovern the kineticresponse of any physi-cal or chemical transi-tion observed in DSC.



This equation shows that the total DSC heat flowis comprised of two components- one which isheating rate dependent [Cp (dT/dt)], and anotherwhich is dependent only on absolute temperature[f(t,T)]. In other words, there is one component(heat capacity component) which directly followsthe modulated heating rate and one componentwhich does not follow heating rate (kineticcomponent). MDSC� measures the total heatflow and separates it into these two components.

A typical �raw� MDSC experimental heat flowcurve is shown in Figure C.4. The deconvolutedresults are shown in Figure C.5. Deconvolutionis performed in real time by Discrete FourierTransformation software which resides in theDSC instrument.

Figure C.4Typical �Raw� MDSCHeat Flow Curve

Appendix C


Figure C.5Deconvoluted Results



SignalDeconvolution

How Signalsare Generated

Signal deconvolution is the process of separatingthe raw data signals (Modulated Temperatureand Modulated Heat Flow) into the average andamplitude (total change in temperature and heatflow values). In MDSC, this signal separation isaccomplished by a mathematical techniqueknown as Discrete Fourier Transformation*.

The DFT technique is used to determine themeasured amplitude of the sample temperatureand heat flow modulation by comparing the rawmodulated data to a reference sine wave of thesame frequency.

The DFT software in the DSC instrumentcontinually measures the amplitude of the sinewave modulation in the raw sample temperatureand raw heat flow signals. Using these ampli-tudes, the Heat Capacity signal is calculated bythe following equation:

Cp = KCp * (Qamp/Tamp) * (Period/2π)

* For a description of the Discreet Fourier Transfor-mation technique, see Press, W.H.; Flannetry, B.P.;Teukolsky, S.A.; and Vetterling, W.T., NumericalRecipes, The Art of Scientific Computing, 1986,Cambridge University Press, Cambridge, pp. 386-390.

Appendix C


where:C

p= Heat Capacity (mJ/°C)

KCp = Heat Capacity CalibrationConstant

Qamp = Heat Flow Amplitude (mW)Tamp = Temperature Amplitude

(°C)Period = Modulation Period (sec)

Given the Heat Capacity signal (Cp), the Revers-ing Heat Flow is calculated by multiplying -Cp bythe programmed (underlying) heating rate. Theminus sign simply inverts the heat flow signal sothat endothermic peaks are plotted in the down-ward direction. The deconvoluted Temperatureand Total Heat Flow signals are computed overone complete cycle of the respective rawmodulated signal. The Nonreversing Heat Flowis computed as the difference between the TotalHeat Flow and the Reversing Heat Flow.

Visual Interpretationof Modulated Heat Flow

Inspection of the Modulated Heat Flow trace inFigure C.4 (see page C-15) and the resultantdeconvoluted signals in Figure C.5 (see page C-16), reveal visually how the deconvolutionprocess works.

It is evident that the Reversing Heat Flow signal(Figure C.5) is proportional to the amplitude ofthe heat flow oscillations (Figure C.4), and thatthe Nonreversing Heat Flow is proportional tothe baseline shift of the oscillations. As the heatcapacity of the PET sample increases throughthe glass transition at 25 min (75°C), the ampli-tude widens in Figure C.4 which results in an



increase in the Reversing Heat Flow (FigureC.5). During the recrystallization peak at 35 min(125°C), the amplitude remains essentiallyconstant, but the baseline of the Modulated HeatFlow shifts up during the transition. Therefore,this transition does not involve a change in theheat capacity of the material, and is manifestedas a peak in the Nonreversing Heat Flow.

Appendix C


Obtaining MultipleHeating Rate Information

It is often helpful to plot the raw Modulated HeatFlow signal (Figure C.4 on page C-15) alongwith the deconvoluted signals (Figure C.5). Byobserving the modulation �envelope� (FigureC.6), you can usually see the transitions that areobserved in the deconvoluted signals.

Figure C.6Quenched PolyethyleneTerephthalate HeatFlow Envelope

The envelope is defined by two boundary curves,one of which passes through all of the modula-tion peak maxima, and another which passesthrough all of the peak minima. The modulationenvelope boundaries correspond to

Heat flow at slowest rate

Heat flow at fastest rate

Heat flow at average rate



the total DSC heat flow at the slowest andfastest heating rates during each modulationcycle. The upper boundary is the heat flowcorresponding to the slowest instantaneousheating rate, which may be a slow heating rate,isothermal or even a negative heating (cooling)rate. The lower boundary corresponds to thefastest instantaneous heating rate, which nor-mally shows the highest heat flow sensitivity.The midpoint of the envelope (the average heatflow) corresponds to the underlying or pro-grammed ramp heating rate.

Analysis of the curves shown in Figures C.4 andC.5 near the glass transition illustrates theseheating rate effects. Figure C.4 shows that theslowest heating rate during the glass transitionwas approximately 0.5°C/min and the fastestrate was approximately 9.5°C/min. Examinationof Figure C.5 indicates that the nonreversingrelaxation peak is clearly visible and is approxi-mately the same size in all three curves. How-ever, the baseline shift due to the change in heatcapacity is virtually nonexistent in the upper(slowest rate) curve but is very pronounced inthe lower (fastest rate) curve. This result is asexpected since the upper curve is associatedwith a very slow heating rate (0.5°C/min) andthe lower curve results from a relatively fastheating rate (9.5°C/min).

Just as the first derivative of a linear temperatureincrease corresponds to the linear heating rate,the first derivative of the Modulated Tempera-ture (Figure C.4) corresponds to the ModulatedHeating Rate. Using this signal as a guide forselecting Modulated Heat Flow data points at aconstant instantaneous heating rate, it is possibleto create a total heat flow curve that corre

Appendix C


sponds to any heating rate between the slowestand fastest rates during each modulation.Transition temperatures correspond to theunderlying heating rate. This approach permitsthe observation of heat flows at multiple heatingrates from a single DSC scan. For example, ifthe lowest heating rate is zero degrees perminute, then the top of this signal should look likethe nonreversing signal (kinetics component)because the heat capacity term goes to zerowhen the heating rate goes to zero.

Using MDSCTM

This section describes how to use MDSC foranalyzing materials. However, specific recom-mendations on analysis conditions for differenttypes of transitions are covered beginning onpage C-68. Before analyzing actual samples, theMDSC unit should be calibrated as described inthe calibration section.

Selecting MDSCMode and Signals

In order to use MDSC, you must select theMDSC mode of operation. This is accomplishedby the following sequence of commands:

1. Select Parameters/Mode found on theThermal Solutions�Instrument ControlMain Menu.

2. Select �Modulated� mode from the drop-down list. See the Thermal Solutions UserReference Guide for further details.



Immediately after selecting the MDSC� mode,a list of possible signals will be displayed. Up toa maximum of eleven signals can be selected tobe saved. The names, units and definitions foreach signal are shown in Table C.1.

Table C.1MDSC Signals

Name Default DefinitionUnits

Time min Time since run start

Temperature* °C Averagesample temperature

Heat Flow* mW Total heat flow (sameas DSC)

Modulated °C Measured sampleTemperature* temperature

Modulated mW Measured heat flowHeat Flow*

Reference radians Modulation sine waveSine Angle* angle

(table continued)

Appendix C


Table C.1(continued)

Name Default DefinitionUnits

Rev Heat mW Deconvoluted heatFlow* capacity component

of the total heat flow

Nonrev mW Kinetic component of Heat the total heat flow Flow*

Heat mJ/°C DeconvolutedCapacity* heat capacity

Temperature °C Amplitude ofAmplitude* temperature

modulation

Heat Flow mW Amplitude of theAmplitude* heat flow modulation

The asterisk (*) following each signal name(except Time) in Table C.1 is not intended as afootnote reference, but is actually part of thesignal name. The asterisk in the name denotesthat the signal is from a Modulated DSCTM

experiment. The asterisk was added to helpdistinguish MDSC experimental output signalsfrom any other signals which may be labeledwith the same or similar names.

The order of the signals shown in Table C.1 isthe order in which data will be stored in the datafile. If fewer than eleven signals are selectedfor storage, the selected n-signals will be shiftedupwards in the table so that the stored signals



run consecutively from 1 to n (e.g., if Nonre-versing Heat Flow is not selected, then HeatCapacity will move to �Sig8/Sig-F�).

At least three signals (Time, Temperature andSignal A) are always stored. Thus, the numberof signals stored ranges from 3 to 11. Switchingto a non-MDSC� instrument mode will changethe number of signals to the standard number forthat mode. Switching back to DSC Modulatedmode will restore the last selection of storedMDSC signals.

In DSC Modulated mode six signals are selectedby default (Time, Temperature, ModulatedTemperature, Modulated Heat Flow, and Refer-ence Sine Angle). Selecting fewer signals willreduce the size of the resultant data file. Select-ing more signals will increase it. Unselectedsignals are not saved on disk or stored in theinstrument RAM memory. Unselected signalscannot be retrieved after run completion. Atfirst, it may seem that storing all signals all thetime is the best approach. Unfortunately, doingso will result in the creation of very large datafiles and the rapid consumption of disk storagespace.

When selecting which signals to store in theMDSC data file it is important to consider thefuture usage of the file. Frequently, to getmaximum utility from the DSC scan, it is neces-sary to evaluate the data in ways that were notanticipated at the time of the experiment.

Appendix C


Also it is sometimes useful to go back to old datafiles and reanalyze them for new information.Signals that seem to be of no value initially (suchas the Reference Sine Angle) may be needed forsubsequent data analysis applications.

The Modulated Temperature, Modulated HeatFlow and Reference Sine Angle signals are thebasic �raw� data signals from the MDSC�experiment and are required for future deconvo-lution of the data. If it is likely that the data willbe analyzed again in the future using a newdeconvolution process, then these three signalsmust be stored in the data file. They cannot beregenerated in post-processing of the data.

Programmed modulation amplitude and fre-quency are not stored in MDSC data files sincethese parameters can change during methodexecution. However, the measured Tempera-ture Amplitude can be stored. If the ReferenceSine Angle is stored, then the modulation periodat any point in time can be computed from thissignal.

For the majority of samples, there will not be aneed to reanalyze the file with a new type ofdata analysis program. Therefore, the storage ofthe following signals is recommended to providecomplete information in the smallest possible file:

� Time� Temperature� Heat Flow� Reversing Heat Flow� Nonreversing Heat Flow� Heat Capacity.



The Modulate Segment

The �Modulate� segment is used to createMDSC� methods. This segment permits theentry of modulation amplitude and period (fre-quency) parameters for use with subsequentramp or isothermal segments. The modulatesegment will automatically appear in the methodeditor segment list when DSC Modulated modeis selected, and disappear when a different modeis selected. The modulate segment has thefollowing format:

Modulate ± <amplitude>°C every<period> seconds

where:

<amplitude> is the peak modulationtemperature amplitude(0.0 to 10.0°C)

<period> is the modulation cycletime (10.0 to 100.0seconds)

For example:

Modulate ±0.500 °C every 40 seconds

Modulate segments execute immediately whenencountered in a method, and simply set themodulation parameters to the new valuesprovided. The last values set are used for allsubsequent ramp and isothermal segments untilnew values are set with another modulatesegment.

Appendix C


Modulation is not performed during set-up typesegments (i.e., jump, equilibrate and initial temp).If no modulate segment has been encountered inthe method before a ramp or isothermal segment,then modulation will remain off. Once turned onby a modulate segment, modulation can beturned back off by inserting a modulate segmentwith a modulation amplitude of zero.

Normal DSC ramps and isothermal periods canbe interleaved with MDSC� ramps and isother-mal periods by turning the modulation on and offwith the modulate segment, as described above.Note, however, that all of the selected MDSCoutput signals are still generated whenever theinstrument is in DSC Modulated mode, even ifmodulation is not enabled in the method. Whenthe modulation amplitude is set to zero, theReversing Heat Flow, Heat Capacity, Tempera-ture Amplitude, and Heat Flow Amplitude signalsare all stored as zero. The Heat Flow, Nonre-versing Heat Flow and Modulated Heat Flow arestored as conventional heat flow.

A typical MDSC method would include thefollowing segments. Actual parameters wouldbe selected based on transitions in the material(see page C-52 for information on selectingexperimental parameters).

1. Equilibrate at 0°C2. Modulate ±1°C every 60 seconds3. Isothermal for 5 minutes4. Ramp 5°C/min to 280°C.



SelectingModulation Amplitude

The purpose of the amplitude parameter in themodulate segment is to select the magnitude ofthe temperature modulation sine wave. Morespecifically, the temperature modulation ampli-tude is the maximum positive or negative tem-perature excursion in degrees from the underly-ing temperature profile during one modulationcycle. The modulation amplitude can be variedfrom 0 to ±10°C.

The temperature modulation imposed on theunderlying temperature profile will produce anaccompanying modulation in the underlyingheating/cooling rate. It is temperature modula-tion and the resultant heat flow oscillation thatare deconvoluted by the MDSC� software toproduce the Reversing Heat Flow, NonreversingHeat Flow and Heat Capacity signals.

The selection of a proper temperature modula-tion amplitude depends on the measurement tobe made. An amplitude of ±1°C is suitable formost heating, cooling or isothermal experiments.Larger amplitudes should be used when measur-ing very weak glass transitions and smalleramplitudes should be used for analysis of melt-ing. The smallest recommended amplitude is±0.1°C. Amplitudes smaller than ±0.03°Cshould be avoided since they are difficult tocontrol. Specific recommended conditions foranalyzing different types of transitions begin onpage C-67.

Appendix C


Cell cooling capacity affects the ability of theinstrument to achieve a selected modulationamplitude. Higher amplitudes and shorterperiods require larger cell cooling capacities.(See �Cooling Devices� on page C-37 for moreinformation on providing proper cell cooling.) Apossible concern when using large amplitudes,especially at low temperatures, is that someamplitude settings cannot be achieved at someperiods. In particular, shorter periods requiresmaller amplitude settings than do longer periods.This is a natural result of the temperature-timeconstant of the DSC cell.

To avoid possible distortion of the heat flow sinewave (see page C-40), it is desirable to selectamplitude settings that are less than the maxi-mum obtainable for the desired modulationperiod. Figure C.7 on the next page shows themaximum recommended amplitudes for 10different modulation periods over the tempera-ture range -150 to 500 °C when using the LiquidNitrogen Cooling Accessory (LNCA).

When using large amplitudes it is wise to verifythat a symmetric sine wave is being generatedby making a trial run with empty pans andobserving the Modulated Heat Flow signal. Sinewave distortion is discussed on page C-40.



Figure C.7Maximum Recommended ModulationAmplitudes and Periods with LiquidNitrogen Cooling Accessory

90 sec

80 sec

70 sec

50 sec

40 sec

30 sec

20 sec

10 sec period

5004003002001000-200

0.05

0.1

0.2

0.3

0.5

0.7

1.0

2.0

3.0

5.0

7.0

10.0

0.07

100 sec

60 sec

-100

Am

plit

ude

(+/-

°C)

Temperature (°C)

Appendix C


SelectingModulation Period

The purpose of the period parameter in themodulate segment is to select the length in timeof the modulation cycle (i.e., the period is theinverse of the modulation frequency). Theoscillation period can be varied from 10 to 100seconds and is automatically controlled.

The most useful period for a particular experi-ment depends on many factors. In general, theperiod should be long enough to provide forquantitative heat transfer between the sampleand sensor, but short enough to permit a reason-able amount of modulation cycles during atransition. For most transitions, it is recom-mended that conditions be set so that a minimumof four (4) modulation cycles occur during theevent. A period of 60 seconds is suggested as astarting point for initial experimentation. Specificrecommended conditions for analyzing differenttypes of transitions begin on pageC-67.

The ability to achieve accurate heat capacitymeasurement is effected by the modulationperiod. Longer periods give more accuratemeasurements. For maximum heat capacityaccuracy, a period of 80 seconds or longer isrecommended.



Signal Time Delays

Modulated DSC� signals are delayed in time by1.5 modulation cycles (1.5 times the modulationperiod). This delay is a natural result of thedeconvolution process that must analyze datapreceding and following each raw data pointbefore the deconvoluted result can be computed.Required digital filtering of the data adds addi-tional delay time. For this reason, MDSC datawill always lag the raw instrument signals(Modulated Temperature and Modulated HeatFlow) by 1.5 cycles. Since the x-axis Tempera-ture signal is a deconvoluted signal, there is notime shift between Temperature and Heat Flow.

SelectingHeating Rate

Heating rate selection in MDSC has the sameeffect on experimental results as in traditionalDSC. Faster heating rates reduce experimenttime and increase DSC sensitivity while gener-ally sacrificing resolution. Slower rates lengthenexperiment time and increase resolution at theexpense of sensitivity.

In the MDSC experiment, there is an even moreimportant effect of the heating rate. It contrib-utes to the number of modulation cycles thatoccur during a transition. In order to get properseparation of the heat flow during a transition, aminimum of four (4) cycles is required. There-fore, if a transition is only 10°C wide, the heatingrate should be no greater than 2.5°C/min (as-suming a period of 60 seconds). The tempera-ture width of a transition should be measuredbetween the onset and end temperature for aglass transition and at the peak half-height for amelt or crystallization.

Appendix C


In practice, MDSC� can be performed at anyunderlying heating or cooling rate, however, ratesof 5°C/min and less are recommended for mostwork. Use lower heating rates to improvetransition resolution or to measure weak glasstransitions.

Special Considerationsin Creating MDSC™ Methods

Ramp Start Temperature

Modulation amplitude is measured and controlledby the DSC module. Some amplitude instabilitywill occur at the beginning of a method segmentas the amplitude control stabilizes. (see FigureC.8 on the next page.) These control oscillationsare not harmful to the heat flow deconvolutionbecause the actual temperature and heat flowamplitudes are measured and used in thedeconvolution calculations. Generally, theseoscillations will dampen completely within 5 to 10minutes after the start of the method segment.

When an MDSC ramp or isothermal segmentstarts execution the modulation amplitude isincreased gradually over the first modulationperiod up to the specified level to prevent heatercontrol overshoot. When this modulation rampup is added to the 1.5-cycle deconvolution delay,plus the time for amplitude control to stabilize,the effect is that several minutes are required forthe MDSC baseline to appear stable in the outputdata. Caution should always be used wheninterpreting results that are within this start-upwindow.



The heat flow signal of an MDSC� ramp start-up looks similar to a glass transition with atrailing relaxation peak (see Heat Flow signal inFigure C.8). All data prior to the return to stablebaseline (the first 5 minutes in Figure C.8) shouldnormally be discounted. To avoid any possibilityof the amplitude stabilization affecting the qualityof a transition, start the ramp at a temperaturethat will provide a five (5) to ten (10) minutestabilization time prior to the transition of interest.

Figure C.8Example of modulationstabilization during rampstart from ambient temperaturewith empty cooling can.

Heating Rate

Temp Amplitude

Heat Flow

Appendix C


Ramp Final Temperature

MDSC� heat/cool ramps are controlled by theunderlying heating rate, and will thereforeterminate when the underlying ramp reaches thespecified final temperature. Deconvolutedtemperature data will appear to terminate 1.5modulation cycles short of the final ramp tem-perature due to the deconvolution processingdelay. This premature ramp termination can becompensated for by increasing the final tempera-ture or by adding an isothermal segment after theramp segment with a duration of 1.5 modulationcycles.

Isothermal MDSC

A unique feature of MDSC is the ability toperform DSC isothermal experiments thatmonitor changes in heat capacity, as well asendothermic and exothermic events, versus time.In this case the reversing signal will be zero dueto the zero underlying heating rate. The TotalHeat Flow signal (and Nonreversing signal) willcontain the heat flow contribution from anynonreversing phenomenon, such as the heat flowdue to a chemical reaction or decomposition.The Heat Capacity signal can be used to monitorchanges in heat capacity during reactions suchas thermoset cure.



Cooling

Cooling Devices

To create the relatively rapid temperaturemodulation, MDSC� is dependent upon cellcooling as well as cell heating. Therefore, formost experiments, a cooling device is needed.There are several alternatives available. MDSCcan be used with the Liquid Nitrogen CoolingAccessory (LNCA) or the Refrigerated CoolingSystem (RCS). It is possible to use air cooling,but data quality will be significantly reduced.Running with the DSC cell exposed to ambientair works well above 100°C, if the ambient airtemperature is not fluctuating, and if the periodsare relatively long and the amplitudes small. Thehigher the temperature of the experiment, thelarger the amplitude that can be obtained.

The Liquid Nitrogen Cooling Accessory (LNCA)can be used to obtain the widest temperaturerange and the largest modulation amplitude. TheLNCA can be used effectively from �150°C upto 500°C. Subambient MDSC� cooling ratesup to 10°C/min can be achieved down to �50°C(5°C/min to �100°C). MDSC� heating rates ofup to 10°C/min can be achieved from �150°C upto 500°C, although rates of 5°C/min or less aremore typical.

Appendix C


Sine Wave DistortionAdequate cooling capacity has a large effect onthe ability to achieve the selected modulationamplitude and avoid sine wave distortion. Forbest results, the heater power should not drop tozero watts or rise above 140 watts during anyportion of the modulation cycle.

Figure C.9 shows a plot of the modulated heatflow signal from three MDSC� heating experi-ments at 5°C/min and a period of 40 seconds. ADSC Cooling Can without coolant was used asthe cooling device. The top scan at ±1.5°Camplitude is symmetric and within the maximumrecommended range for a 40-second period (SeeFigure C.7 on page C-31). The amplitudesettings of ±3.5°C and ±5.0°C cannot be ob-tained under these conditions as shown by thedistortion of the bottom half of each heat flowcycle in the middle and bottom scans.

As stated on page C-37, the quality of the sinewave and deconvoluted signals is greatly re-duced if experiments are run with a DSCCooling Can or compressed air as the coolingsource.

Figure C.9Example of Heat FlowSine Wave Distortion



When sine wave distortion occurs in the modu-lated heat flow signal, the resulting deconvolutedsignals may be distorted, leading to misinterpreta-tion of the data. When using previously untriedcombinations of period, amplitude, and coolingcapacity it is wise to verify that a symmetric sinewave is being generated by making a trial runwith empty pans and observing the ModulatedHeat Flow signal.

Signal DisplayThe Signal Display window shows the MDSC�signals. Both the modulated and deconvolutedsignals are shown. The following signals andunits will be displayed:

� Run time (min)� Segment time (min)� Set point temperature (°C)� Modulated Sig A (mW & mV) {Modulated

Heat Flow}� Offset (mV)� Heater power (watts)� Oscillation period (sec)� MDSC signals 1 through 11 (appropriate

units)� Underlying dT/dt (°C/min)� Percent memory used� LNCA pressure.

When Modulated mode is selected, all MDSCsignals will be displayed, whether selected foroutput or not.

NOTE:

Appendix C


With MDSC� three different temperatures canbe viewed at the same time. The temperaturedisplayed on the instrument is the actual realtimesample temperature (as in conventional DSC).The temperature in the status line is thedeconvoluted temperature (delayed by 1.5cycles). The �Modulated Temperature� is theactual modulated sample temperature after datacompression and sampling interval averaging.Therefore, during a MDSC ramp or isothermalsegment, all three of these temperatures may bedifferent.

Sampling Interval(Data Storage Rate)

Data sampling interval may be set to the samevalues as allowed for conventional DSC (i.e., 0.2to 1000.0 seconds/point). The default is 0.2seconds/point (5 points/second). Increasing thesampling interval will help to reduce the size ofMDSC data files. The maximum samplinginterval of 5 points/second is always used tocalculate the deconvoluted MDSC signals.Therefore, the accuracy of the signals is notcompromised by the data storage rate. A datacollection rate of 1.0 seconds/point is recom-mended for most MDSC experiments.



Calibrating with MDSCTM

DSC CalibrationThe DSC cell calibration procedure for modu-lated DSC is the same as for normal DSC. Thecalibration should be performed at the desiredunderlying heating rate using a conventional DSCrun. Switching between standard and ModulatedDSC does not require a change of calibration. Ifa cooling device is to be used during the experi-ment, then the calibration should be performedwith the cooling device installed on the DSC cell.

Procedure for MeasuringMDSCTM Heat CapacityCalibration Constant [K(Cp)*]

An additional calibration for heat capacity isrequired for accurate heat capacity measure-ments and for proper separation of the TotalHeat Flow signal into its Reversing and Nonre-versing components. The heat capacity calibra-tion is made by analyzing a sample of knownheat capacity and comparing the calculated heatcapacity to the literature value over the tempera-ture range of interest. The heat capacitycalibration constant is entered on the controller.

The conditions of the heat capacity calibrationrun should duplicate the conditions of the samplerun as much as possible (i.e., heating/coolingrate, modulation period and amplitude, coolingdevice, purge gas and flow rate, sample

Appendix C


pans, etc.) For optimum results, the weight ofthe calibration material should be chosen suchthat the total heat capacity of the materialapproximates that of the sample to be studied.Outlined on the next few pages is the recom-mended procedure for MDSC� heat capacitycalibration.

Calibrant

Two calibration samples are provided with theMDSC Heat Capacity Calibration kit. These areeach sapphire discs, cut to different dimensionsbut having similar weights. A different disc isused for standard pans and hermetic pans.

Modulation Conditions

The modulation conditions should be chosen soas to replicate the subsequent experimentalconditions as closely as possible. Commonmodulation conditions include periods of 60-80sec, and modulation amplitudes of + 0.5°C to±1.5°C. An underlying ramp rate of 5°C/min issufficient, however, slower ramp rates may beused.

Temperatureof Measurement

The 25 mg sapphire discs are designed as abroad-temperature range calibrant�they may beused across the entire operating range of theinstrument. However, experimental precisiondeclines as the temperature range expands.Therefore, we recommend calibrating over a150°C range, centered in the normal operatingrange for your experiment. For example, if you



normally operate between 0°C and 300°C,calibrate between 75°C and 225°C. If a broaderrange is desired, it is possible to expand thecalibration range, keeping in mind the decline inthe precision of the measurement.

Calibration andMeasurementProcedure

Following is a suggested procedure for heatcapacity calibration. For this example, we chose:

� a range of 50°C to 200°C,� a modulation amplitude of ±1.0°C,� a modulation period of 60 seconds, and� a ramp rate of 5°C/min.

1. Prepare the sample:

a. Match the weights of the sample panand reference pan to within 0.1 mg.

b. Weigh the appropriate sapphire calibra-tion disc.

c. Record the weight.

d. Encapsulate the disc in the pan.

e. Crimp the lid onto the empty referencepan.

2. Create and load the following method:

a. Equilibrate at 30°C.

Appendix C


b. Modulate ±1.0°C every 60 seconds.

c. Ramp 5°C/min to 210°C.

A 25°C lower starting temperature is pro-grammed to allow five minutes for modulationconditions to stabilize. A 10°C higher termina-tion temperature is programmed to allow forthe 1.5 cycle deconvolution delay.

3. Select DSC Modulated mode, and make surethe Heat Capacity signal is saved.

4. Set the MDSC Heat Capacity Constant equalto 1.00 as follows:

RMX Users:

a. Select GoTo Experimental Param-eters.

b. Select GoTo Module Parameters.

c. Enter �1.00� in �MDSC Heat CapacityConstant.�

Thermal Solutions Users:

a. Select Parameters from the MainMenu.

b. Select Cell Calibration.

c. Enter �1.00� in �MDSC Heat CapacityConstant.�

NOTE:



5. Place the encapsulated sapphire disc on thesample side in the DSC cell, and the emptycrimped pan on the reference side.

6. Enter the weight of the sapphire disc inExperimental Parameters, and run the loadedmethod.

7. When the run is finished, plot out the HeatCapacity signal versus Temperature.

8. Generate a Data Table starting at 56.85°Cincrementing by 10°C.

RMX General Analysis Users:

a. Select GoTo Print Report.

b. Select Data Table.

c. Enter Start: 56.85°CStop: 246.85°CIncrement: 10°C

d. Accept this form and send results toPrinter.

Universal Analysis Users:

a. Select View.

b. Select Data Table.

c. Enter Start: 56.85°CStop: 246.85°CIncrement: 10°C

d. Accept this form and send results toPrinter.

Appendix C


The printer will output a data table similar to theone below:

Temperature* Heat Capacity* °C J/g/°C

56.85 0.6850 66.85 0.7112 76.85 0.7325 86.85 0.7516 96.85 0.7694106.85 0.7871116.85 0.8031126.85 0.8189136.85 0.8328146.85 0.8447156.85 0.8567166.85 0.8678176.85 0.8771186.85 0.8869196.85 0.8960206.85 0.9051216.85 0.9154226.85 0.9271236.85 0.9373246.85 0.9482

9. Compare each value of Heat Capacity to theliterature value in Table C.3, AluminumOxide Specific Heat, beginning on the nextpage. (This table is also available in theTechnical Reference section of the DSCOperator�s Manual.)

Table C.2Heat CapacityExample



Table C.3Aluminum OxideSpecific Heat*

Cp°C K J/g°C

�183.15 90 0.0949�173.15 100 0.1261�163.15 110 0.1603�153.15 120 0.1968�143.15 130 0.2349�133.15 140 0.2739�123.15 150 0.3134�113.15 160 0.3526�103.15 170 0.3913 �93.15 180 0.4291 �83.15 190 0.4659 �73.15 200 0.5014 �63.15 210 0.5356 �53.15 220 0.5684 �43.15 230 0.5996 �33.15 240 0.6294 �23.15 250 0.6579 �13.15 260 0.6848 �3.15 270 0.7103 0.00 273.15 0.7180 6.85 280 0.7343 16.85 290 0.7572 26.85 300 0.7788 36.85 310 0.7994 46.85 320 0.8188 56.85 330 0.8373 66.85 340 0.8548

*Taken from D.A. Ditmars, et al,J. Res. Nat.Bur. Stand., Vol 87, No. 2,pages 159�163 (1982). This is a publicdomain publication.

(table continued )

Appendix C


Table C.3 Aluminum Oxide Specific Heat(continued)*

°C K J/g°C

76.85 350 0.8713 86.85 360 0.8871 96.85 370 0.9020106.85 380 0.9161116.85 390 0.9296126.85 400 0.9423136.85 410 0.9545146.85 420 0.9660156.85 430 0.9770166.85 440 0.9875176.85 450 0.9975186.85 460 1.0070196.85 470 1.0161206.85 480 1.0247216.85 490 1.0330226.85 500 1.0409236.85 510 1.0484246.85 520 1.0557256.85 530 1.0627266.85 540 1.0692276.85 550 1.0756286.85 560 1.0817296.85 570 1.0876306.85 580 1.0932316.85 590 1.0987326.85 600 1.1038336.85 610 1.1089


(table continued )

Cp



Table C.3 (continued)*

Cp°C K J/g°C

346.85 620 1.1137356.85 630 1.1183366.85 640 1.1228376.85 650 1.1271386.85 660 1.1313396.85 670 1.1353406.85 680 1.1393416.85 690 1.1431426.85 700 1.1467446.85 720 1.1538466.85 740 1.1604486.85 760 1.1667506.85 780 1.1726526.85 800 1.1783546.85 820 1.1837566.85 840 1.1888586.85 860 1.1937606.85 880 1.1985626.85 900 1.2030646.85 920 1.2074666.85 940 1.2117686.85 960 1.2159706.85 980 1.2198726.85 1000 1.2237746.85 1020 1.2275766.85 1040 1.2312786.85 1060 1.2348


(table continued )

Appendix C


Table C.3 AluminumOxide Specific Heat(continued)*

°C K J/g°C

806.85 1080 1.2383826.85 1100 1.2417846.85 1120 1.2451866.85 1140 1.2484886.85 1160 1.2516906.85 1180 1.2548926.85 1200 1.2578976.85 1250 1.26531026.85 1300 1.27241076.85 1350 1.27921126.85 1400 1.28561176.85 1450 1.29171226.85 1500 1.29751276.85 1550 1.30281326.85 1600 1.30791376.85 1650 1.3128


10. Calculate the MDSC Heat Capacity Con-stant at each temperature using the followingequation:

K(Cp) = Lit. Value/Observed Value

For example, at 56.85°C, the value of K(Cp)is calculated as follows:

K(Cp)56.85°C = 0.8373/0.6850 = 1.22

Cp



11. Calculate the average of all the values ofK(Cp). This average value is the MDSCHeat Capacity Constant, K(Cp)*.

12. Enter the calculated value of K(Cp)* in theappropriate field.

RMX Users:

a. Select GoTo Experimental Param-eters .

b. Select GoTo Module Parameters.

c. Enter value in �MDSC Heat CapacityConstant.�

Thermal Solutions Users:

a. Select Parameters from the MainMenu.

b. Select Cell Calibration.

c. Enter value in �MDSC Heat CapacityConstant.�

The MDSC is now calibrated for heat capacity.

Appendix C


MeasuringHeat Capacity

To obtain accurate heat capacity measurements,the DSC cell must be calibrated for cell constant,baseline slope, temperature, and heat capacity asdescribed in the calibration section beginning onpage C-41. Heat capacity measurements arethen made as follows:

1. Obtain two pans with lids that are of thesame weight ±0.1 mg. Place the sample intoone of the pans and crimp the lid in place.Recommended weights are as follows:

Polymers 10-15 mgMetals 20-40 mgOthers 10-15 mg

2. Place the sample (and sample pan) to bemeasured on the sample side of the cell andthe matching reference pan on the referenceside.

3. Confirm that the Heat Capacity signal isbeing stored in the data file by selectingParameters/Mode and checking the signalssaved.

4. Create and load a method containing thesame period chosen for the heat capacitycalibration. Start the experiment. Thecalculated heat capacity will be stored in theMDSC� Heat Capacity signal.



5. Use Universal Analysis to observe andreport the sample heat capacity at thetemperature of interest.

Long modulation periods (60 to 100 seconds)should always be used when trying to obtainmaximum heat capacity accuracy. Long periodsresult in heat capacity calibration constantscloser to unity (1.0), in contrast to much largerconstants for short periods.

NOTE:

Appendix C


Guidelines for Running MDSC™Experiments

BackgroundMDSC is a dynamic technique that has signifi-cant advantages over traditional DSC tech-niques. These advantages result from thedifferent operating principles of MDSC wherethe heating or cooling rate is modulated ratherthan held constant. Transitions (glass transition,melting, crystallization, etc.) have both kineticand thermodynamic properties. The operatingconditions of MDSC can be optimized to allowyou to more easily detect and separate theseproperties.

In this section we will suggest �typical� operatingconditions for different types of transitions.Keep in mind that these �typical� conditions areonly starting points. Some materials will behavedifferently than others and it is up to you tofurther define the conditions for your particularsamples.



GeneralSample Preparation

The ability of MDSC� to separate overlappingtransitions and to provide very high sensitivity fordetection of weak transitions is totally dependenton the transfer of heat from the sample to thesensor. Therefore, some of the basic rules thatapply to traditional DSC must be strictly fol-lowed. These include:

1. Maximize the contact area between thesample and the pan.

To do this you must keep the sample as thinas possible in order to cover as much of thepan as possible. Do not use large irregularchunks of sample.

2. Use lids on the DSC pans to keep thesample flat and pressed against thebottom of the pan.

When using hermetic pans, flatten the lidbefore crimping to force the sample to thebottom of the pan and to minimize its abilityto move during the experiment.

3. Use samples of 10-15 mg for polymersand keep them as thin as possible.

Although 10-15 mg is larger than typicallyused for traditional DSC experiments, it isrecommended for MDSC in order to provideaccurate heat capacity and to maximize thesize of the total and nonreversing signals thatcan be smaller than typical DSC measure-ments. This is due to the much loweraverage heating rates used with MDSC.

Appendix C


General MDSC™Operating Parameters

Use the following general operating parametersin order to get useful results for most samples.

1. Set up the following experimental method:

In order to give the entire system time tocome to equilibration at the starting tempera-ture, a 5-minute isothermal segment (as seenin step c below) is recommended.

a. Equilibrate at start temperatureb. Modulate ±1°C every 60 secondsc. Isothermal for 5 minutesd. Ramp 5°C/min to final temperature.

2. Use an Amplitude of ±1°C

The larger the oscillation amplitude, thehigher the sensitivity for detecting weaktransitions. For broad, weak transitions, suchas the glass transition of polypropylene ornylon fiber, it may be necessary to increasethe amplitude to ±2°C. For melting transi-tions, small amplitudes are used so that thereis no cooling (decreasing temperature) of thesample during the experiment. See TableC.4 on page C-73 for amplitude selection.



The ability to use amplitudes larger than±2°C depends on the temperature of theexperiment and on the time period of thetemperature oscillation (see Figure C.7 onpage C-31). In general, ±2°C providessufficient sensitivity even for the weakest oftransitions.

3. Use an oscillation period ranging from40 to 60 seconds.

For most samples, 60 seconds is the recom-mended period of oscillation. For narrowtransitions, such as fast melts, use shorterperiods. Periods of 30 seconds or less aregenerally not recommended. Remember touse small amplitudes when selecting shortperiods. For long periods it is necessary touse slower heating rates in order to achievea minimum of four oscillations over thetemperature range of the transition. Heatcapacity must be calibrated at the periodchosen. Use of helium purge gas, at ap-proximately 25 mL/min, permits use of 40-second periods because the helium is morethermally conductive than nitrogen. Whenavailable, helium is the preferred purge gasfor MDSC� experiments.

4. Set the Heating or Cooling rate to 1 to5°C/min.

The maximum practical heating rate is5°C/min. (Use slower rates if you want toincrease resolution.) The ideal heating rateis one that will provide a minimum of fourtemperature oscillations over the tempera-ture range of the transition. For example, if

Appendix C


the transition being studied is 15°C widefrom the extrapolated onset to the extrapo-lated endset, the maximum heating rate (with60 second period) should be less than 4°C/min.

maximum rate = 1 osc/min X15°C/4 oscillations = 3.75°C/min

To increase the number of modulation cyclesduring a transition, and to enhance separa-tion, use a slower heating rate.



Example MDSCTM

ExperimentIn this example two DSC scans of quenchedpolyethylene terephthalate (PET) were run innitrogen to compare the results using conven-tional DSC and Modulated DSC.

Experimental Conditions

The DSC was calibrated for cell constant,baseline slope, and temperature using indium.The heat capacity calibration was performedusing high density polyethylene (HDPE) asdescribed in the section �Procedure for Measur-ing MDSCTM Heat Capacity Calibration Constant[K(Cp)*]� on page C-41.

A sample of PET film was weighed and placedinto a standard aluminum sample pan withcrimped lid. A matching empty sample pan withcrimped lid was used as the DSC reference.The sample was conditioned prior to each run byheating the sample to 280°C in the DSC cell andimmediately quench-cooling it to room tempera-ture by placing it on the aluminum surface of theDSC cell base. A liquid nitrogen cooling acces-sory (LNCA) was used for the experiment.

In the first scan (Figure C.10) a conventionalheating rate of 5°C/min from ambient to 290°Cwas used for the method. In the second scan(Figure C.11) a modulated DSC ramp at 5°C/minfrom ambient to 290°C was used for the method.The modulation amplitude was ±0.53°C. Themodulation period was 40 seconds. All signalswere selected for data storage.

Appendix C


Figure C.10PET Sample UsingConventional Heating Rate

Figure C.11PET Sample Usinga Modulated DSCRamp



Observations

Primarily, it is noted that the standard DSCresults and the Total Heat Flow signal fromMDSC are quantitatively and qualitativelyequivalent within normal experimental error.

� Glass Transition:

The glass transition at 70 °C is due to theamorphous structure in the quenched sample.The increase in molecular mobility that occurs atthis temperature results in an increase in heatcapacity that can be seen in the Reversing HeatFlow signal. At the same temperature, anenthalpic relaxation occurs. Since this is akinetic process, the endothermic peak is seen inthe Nonreversing Heat Flow signal.

� Cold Crystallization:

The peak observed at 125°C is due to thecrystallization of the amorphous phase. Sincethis is a kinetic process, the peak is observedonly in the Total Heat Flow and NonreversingHeat Flow signals. A close examination of theReversing Heat Flow signal shows a smallpositive shift in the baseline near 135°C due tothe small decrease in the sample heat capacityas it changes from amorphous to crystalline.

� Melting:

A melting peak is present in the Total Heat Flowsignal at 250°C. The irregular shape of the meltis due to an ongoing process of crystallizationand crystal perfection prior to and during themelt. These processes are clearly evident in theNonreversing Heat Flow signal. Because these

Appendix C


crystallization processes are exothermic, theymake it impossible to detect the real onset ofmelting (endothermic) in the Total Heat Flowsignal. The Reversing Heat Flow signal clearlyshows that melting begins as low as 150°C.

Applications

The broad capability of Modulated DSC� as avaluable tool for materials research and productdevelopment is illustrated by these representativeapplications.

Separation of OverlappingReversing and NonreversingThermal Transitions

In thermosets and semicrystalline/amorphousthermoplastics, processing can result in internalmolecular stresses (thermal history effects)which are relieved on reheating. The release ofthese stresses sometimes appears as a smallendothermic relaxation event after the glasstransition. The close proximity of the endo-therm to the glass transition can make interpreta-tion difficult as shown for a B-stage epoxy (solidline) in Figure C.12 on the next page. MDSC onthe other hand, separates the glass transition,which is a reversing phenomenon, from theendothermic relaxation, which is a nonreversingphenomenon. This separation greatly improvesinterpretation.



Figure C.12B-Stage Epoxy

Traditionally, thermal history effects such as theendothermic relaxation peak are eliminated by�pretreating� the material [heating above theglass transition (Tg) and then slowly cooling]before evaluation. However, in thermosets, thistype of pretreatment can advance cure and alterthe results. MDSC� helps to alleviate thisproblem.

Figure C.13, on the next page, shows anotherexample where MDSC improves separation andinterpretation. The sample is a blend of polycar-bonate (PC), polyethylene terephthalate (PET),and high-density polyethylene (HDPE). TheTotal Heat Flow signal shows a glass transition(T

g) near 80°C, but the large transition at 120°C

is somewhat indecipherable. MDSC demon-strates that this complex thermogram actuallycontains two glass transitions, the PET Tg atapproximately 75° and the PC Tg at approxi-mately 145°C, as well as the HDPE melt at

Appendix C


approximately 120°C. These transitions involvechanges in the heat capacity of the material, andare thus resolved in the Reversing Heat Flowsignal. The cold crystallization of the PEToccurs simultaneously with the HDPE melt, butis resolved in the Nonreversing Heat Flow signal.Thus, MDSC is easily able to resolve complexand overlapping transitions, resulting in moreaccurate interpretation.

Figure C.13Example of MDSCTM

Improvement of Separation



Increased Sensitivityfor Detection ofGlass Transitions

Typically, glass transition (Tg) measurements inhighly filled or reinforced polymers are difficultby conventional DSC. This is because Tg

measurement is based on detection of a heatcapacity change, and the addition of fillers andreinforces �dilutes� (weakens) the change beingmeasured. Modulated DSC��s high sensitivitypermits the detection of a very subtle Tg.

Figure C.14 shows the MDSC results for afiberglass reinforced composite material. TheTotal Heat Flow signal, which is comparable tothe typical standard DSC result, exhibits a veryweak, nearly non-discernible transition. TheReversing Heat Flow signal, which is based ondirect heat capacity change, resolves this weaktransition into a measurable Tg.

Figure C.15 illustrates the MDSC results for theglass transition of a nylon pellet with varyingdegrees of moisture. Moisture content canaffect the temperature and intensity of the glasstransition. The improved sensitivity of MDSCallows for the detection of these subtle shifts, asdemonstrated in Figure C.15.

Specific recommended conditions for analyzingdifferent types of transitions begin on pageC-71.

Appendix C


Figure C.14Tg of Fiberglass-Reinforced Composite

Figure C.15Effect of Moisture onthe Tg of Nylon



Direct Measurementof Heat Capacity

Heat Capacity (Cp) measurement by conven-tional DSC is a tedious process requiring multipleexperiments and considerable operator expertiseto obtain results with reasonable accuracy andprecision. MDSC� provides the unique abilityto measure heat capacity directly in a singleexperiment, even at very slow underlying heatingrates.

Figure C.16 below shows the results from threeseparate MDSC evaluations of polystyrene. Thecrosses indicate reported literature Cp values atseveral temperatures for comparison. The glasstransition is present as a step change in heatcapacity at about 100°C. The table in the upperleft hand corner of the figure compares thetypical precision and noise, as well as the numberof experiments, associated with heat capacitymeasurements by conventional DSC (based onASTM round-robin results) and MDSC. MDSCprovides better results in less experimental time.

Figure C.16Heat Capacityof Polystyrene

Appendix C


IsothermalCure Evaluation

Modulated DSC� has the ability to generate aninstantaneous heating rate during isothermalexperiments which allows measurements to bemade that are not possible in conventional DSC.The results for a high-temperature epoxy curedisothermally at 90°C (Figure C.17) illustrate thispoint. The solid line is the Nonreversing HeatFlow. It indicates an exothermic peak whichrepresents the Heat of Cure equivalent to thatseen by conventional DSC. The dashed line isthe Heat capacity signal.

Figure C.17Epoxy IsothermalCure Evaluation



In theory, heat capacity should decrease as themonomer polymerizes because polymerization, orcross-linking, causes the internal molecularmotion to decrease (in contrast to the heatcapacity increase observed at Tg during heatingin an amorphous polymer). The MDSC� heatcapacity does decrease as expected. However,the onset of heat capacity decrease occurs afterthe exothermic peak maximum in the Nonrevers-ing Heat Flow signal. This means that heatcapacity changes more dramatically duringcross-linking (the final stage of cure) than duringlinear polymerization (the first stage of cure).Evaluation by dynamic mechanical analysis(DMA) supports this conclusion since thestorage modulus (dash-dot line) increases at thesame temperature as the heat capacity begins todecrease.

Direct Measurementof Thermal Conductivity

Thermal conductivity is a measure of the ease atwhich heat is transmitted through a material andis a basic material property. Determination of amaterial�s thermal conductivity is important inevaluating its utility for specific applications. Inmany of these applications, a textbook value or asingle measurement near the temperature of useis sufficient to make a decision. In a few cases,however, the material�s composition varieswidely enough that regular measurement ofthermal conductivity is required.

Appendix C


As discussed previously, MDSC� has the abilityto directly measure heat capacity of a material,and can also directly monitor heat capacitychanges as a function of temperature. Sinceheat capacity and thermal conductivity arerelated properties, MDSC can be used to directlymeasure the thermal conductivity of certaininsulating materials including polymers, ceramicsand glasses This is performed by measuring asample�s specific heat capacity directly viaMDSC. The apparent heat capacity of a largersample of the same material of known weightand dimension is then measured. These valuesare then substituted into an algebraic equationwhich calculates the sample�s thermal conductiv-ity. Specific directions and a reference materialkit for thermal conductivity are available fromTA Instruments.



Specific MDSC™ OperatingParameters for DifferentTransitions or Properties

Glass Transition

MDSC� is a much better technique thanconventional DSC for measuring glass transi-tions. This is attributed to two major factors:

� elimination of the volume relaxation peak,

and

� elimination of baseline slope and curvature.

To get the best results from MDSC, the follow-ing experimental conditions are recommended:

� Amplitude = ±1°CUse larger values (up to ±3°C) for veryweak transitions.

� Period = 60 seconds

� Heating RateUse a rate up to 5°C/min. Use lowerheating rates if necessary to achieve atleast four modulation cycles over thetemperature range of the transition.

� Crimped aluminum pans (matched ±0.1 mg).

� Helium purge at 25 mL/min.

Appendix C


� 10-30 mg sample weight.

� 1 sec/point data collection rate.

Polymer Melting(Initial Crystallinity)

MDSC� has the ability to separate melting(reversing) transitions from simultaneous crystal-lization (nonreversing) transitions. This providesfor more accurate onset temperatures, as well asmore accurate and precise heats of fusion andheats of crystallization.

� Heating Rate = 5°C/min

� Period = 40-60 secondsUse longest period possible to achieve atleast 4 modulation cycles at half-height ofthe melting peak.

� AmplitudeSelect maximum amplitude for �heatingonly� conditions as shown in Table C.4 onthe next page.

� Crimped aluminum pans (matched ±0.1 mg).

� 10-15 mg sample weight.


� 1 sec/point data collection rate.



Table C.4Maximum�Heat Only�Amplitude

Heating Rate (°C/min)

0.1 0.2 0.5 1 2 5 10

10 0.003 0.005 0.013 0.027 0.053 0.133 0.26520 0.005 0.011 0.027 0.053 0.106 0.265 0.53130 0.008 0.016 0.040 0.080 0.159 0.398 0.79640 0.011 0.021 0.053 0.106 0.212 0.531 1.06250 0.013 0.027 0.066 0.133 0.265 0.663 1.32760 0.016 0.032 0.080 0.159 0.318 0.796 1.59270 0.019 0.037 0.093 0.186 0.372 0.929 1.85880 0.021 0.042 0.106 0.212 0.425 1.062 2.12390 0.024 0.048 0.119 0.239 0.478 1.194 2.389100 0.027 0.052 0.133 0.265 0.531 1.327 2.654

Tamp

= Hr * (P/2p * 60)

where:

Tamp= Maximum temperature amplitude for�heat only� (°C)

Hr = Average heating rate (°C/min)p = period (seconds)60 = converts seconds to minutes.

Per

iod

(sec

)

Appendix C


NonreversingTransitions

These include cold crystallization, enthalpicrelaxations, thermoset cure, protein denaturation,and decomposition.

Use same conditions as those for melting exceptuse an amplitude of ±1°C since cyclic heatingand cooling does not affect results.

Heat Capacity &Thermal Conductivity

Modulated DSC� is unique in its ability toinstantaneously measure heat capacity. Thisability can be utilized in the direct measurementof thermal conductivity of some materials.

� Heating RateNot important (0-5°C/min) except in themelting region where lower heating ratesresult in lower heat capacity values.

� Period = 80-100 SecondsShorter periods can be used but samplethermal conductivity can affect results to agreater extent at shorter periods.

� Amplitude = ±1 to 2°C

� Calibration with material of similar Cp andthermal conductivity, using identicalexperimental conditions.

� Crimped aluminum pans (matched within±0.1 mg).



� Sample weight 10-15 mg polymers; 15-20mg sapphire; 20-30 mg metals.


� 1 sec/point data collection.

Appendix C


Index

TA Instruments DSC 2920 CE I�1

Index

A

Accessories 1-12. See alsoindividual accessory names

DSC Cooling Can 1-14heat exchanger 1-13LNCA 1-13Refrigerated Cooling System 1-14Sample Encapsulating Press 1-12setting up 3-24

Address selector dial 2-10

Air coolsetting up 3-24

Applications for the DSC 4-8

AtmosphereStandard DSC cell 1-17

Autofill (status code) 4-9

B

Baseline calibration 3-5

Baseline noise 1-18

C

Cablesconnecting 2-9

Calib (status code) 4-9Calibration 3-4

baseline slope and offset 3-5cell constant 3-6crosstalk 3-7for dual sample DSC cell 3-7in MDSC C-41

procedure C-43temperature 3-7

CE compliance information xi

Cellcleaning of contamination 5-5Dual Sample 1-11Standard DSC 1-10

Cell constant calibration 3-6in MDSC C-41

Chemical safety xv

Cleaning 5-4contaminated cell 5-5DSC pans 5-6routine 5-4

Cold (status code) 4-9

Complete (status code) 4-10

Confidence test2-23explanation 5-11–5-15

Connector panel 2-10

Index

I�2 TA Instruments DSC 2920 CE

Controllerfunctions 3-22

Coolingin MDSC C-37

Cooling (status code) 4-10

Cooling gas fitting 2-14

Cooling gas lineconnecting 2-13

Crosstalk calibration 3-7

D

Differential heat flow 1-10

DSC 2920 CEaccessories 1-12–1-19. See

also individual accessorynames.

address selector dial 2-10cable and gas line connec-

tions 2-9cell block heating 4-6cleaning 5-4

pans 5-6confidence test 2-23, 5-12–5-14description 4-3display 2-24drying 2-8installing 2-7limitations C-8location for 2-8maintenance 5-4Modulated mode.See MDSCpower cable 2-14

DSC 2920 CE (cont'd)principles of operation 4-6–4-8repacking 2-6replacement parts 5-15sample types 4-8shutting down 2-25specifications 1-16starting up 2-23status codes

explanations 4-9test functions 5-11unpacking 2-3

DSC Cooling Can 1-14applications 3-29function 1-14installation 2-21operation 3-30–3-31setting up 3-25

DSC Standard Celldescription 4-4installation 2-16

for subambient operation 2-20pan positions 3-26specifications 1-17

Dual Sample DSC Cellcalibration for 3-7description 4-4function 1-11installation 2-16

for subambient operation 2-20pan positions 3-27specifications 1-19

E

Electrical safety xiii

Index


Equilib (status code) 4-10

Err n (status code) 4-10

Experiment(s) 3-8basic procedure 3-8sample loading 3-26sample preparation 3-9setting up 3-22setting up accessories 3-24starting 3-28stopping 3-28in MDSC

examples C-59guidelines C-54sample preparation C-55

F

Furnacepower check 5-9

Fuses 5-8

G

Gas Switching Accessorysetting up 3-25

Glass transitionsin MDSC

detection of C-65examples C-61operating parameters C-71

GPIB cableconnecting 2-9

H

Heat capacitycalibration

in MDSC C-43calibration constant 4-13

in MDSC C-41measurement

in MDSC C-67, C-74 measurement procedure

in MDSC C-52

Heat exchanger 1-13

HEATER indicator light 5-10

HEATER Switch 1-9, 5-9

Heating (status code) 4-10

Helplines to TA Instruments x, B-2

Hermetic sample pans 3-13preparing 3-19setting up the Press for A-6

Holding (status code) 4-10

Hot (status code) 4-10

I

Initial (status code) 4-10

Inspecting the DSC 2920 CEfor routine maintenance 5-4upon arrival 2-7

Installing the DSC 2920 CE 2-7

Index


Iso (status code) 4-10, 4-11

Iso-track (status code) 4-11

Isothermal MDSC C-36cure evaluation C-68

J

Jumping (status code) 4-11

K

Keypad 1-5

Keysreject 1-8SCROLL 1-7START 1-7stop 1-7

L

Labels on instrumentxii

Lifting instrument safely xvi

LNCA 3-25function 1-13setting up 3-25

M

MDSCadvantages C-9applications C-62background C-8calibration C-41

procedure C-43

MDSC (cont'd)capabilities C-5compared with DSC C-8cooling C-37creating methods

special considerationsC-34–C-36

description C-5Discrete Fourier

Transformation C-17experimental procedure C-23experiments

examples C-59guidelines C-54sample preparation C-55

general operating parametersC-56

glass transitions C-65examples C-61operating parameters C-71

heat capacity C-67, C-74measurements C-52

heat capacity calibration C-41procedure C-43temperature of measurement

C-42heat flow C-15increased resolution C-10installation C-7isothermal C-36isothermal cure evaluation C-68modulate segment C-27modulated heat flow C-18, C-19nonreversing transitions C-74polymer melting C-72principles of operation C-12ramp segment C-34sample preparation C-55sampling interval C-40selecting heating rate C-33

Index


Partsordering B-1replacement 5-15

Power cableconnecting 2-14

Power problemsfuses 5-8HEATER indicator light 5-10power failures 5-11

POWER Switch 1-9

Purge fitting 2-12

Purge gassetting up 3-24

Purge lineconnecting 2-12

Q

Quantitative studies from DSCexperiments 4-13

Quench-cooling between runs 3-30

R

Ramp Final Temperaturein MDSC C-36

Ramp Start Temperaturein MDSC C-34

Ready (status code) 4-11

MDSC (cont'd)selecting mode C-22selecting modulation amplitude

C-29selecting modulation period C-32selecting signals C-22signal deconvolution C-17signal time delays C-33sine wave distortion C-38thermal conductivity C-74typical method C-28when to use C-8

Methods 3-22

Modulate segmentin MDSC C-27

Modulated DSC C-5. See alsoMDSC.

N

Nitrogenhandling safety xiv

No Power (status code) 4-11

Nonhermetic pans 3-13preparing 3-16setting up the Press for A-2specifications A-5

P

Pan. See pan type (e.g., Sample pan).

Index


Reference pan 3-20

Reference thermocouple 4-7

Refrigerated Cooling Systemsetting up 3-25

REJECT 3-28

Reject (status code) 4-11

Repeat (status code) 4-11

Resolutionincreasing with MDSC C-10

S

Safety xiCE specifications xichemical xvelectrical xiiiinstrument label xiilifting the instrument xviliquid nitrogen xivstandards xithermal xvi

Sampledetermining size 3-9encapsulation 3-15hermetically sealed 3-21loading 3-26non-hermetically sealed 3-16pan selection 3-11.See also

Sample panphysical characteristics 3-10preparation 3-9

in MDSC C-55

Sample (cont'd)size 3-9

for standard DSC cell 1-17volatile liquids 3-13

Sample Encapsulating Press 1-12,3-15

description A-1maintenance 5-6selecting a method 3-15setting up for hermetic sealing

A-6setting up for nonhermetic

sealing A-2

Sample informationentering 3-22

Sample pan 3-11, 3-12characteristics 3-10configurations 3-13covering 3-17encapsulating 3-15hermetic 3-13

preparation 3-19loading 3-26materials 3-11nonhermetic 3-13

preparation 3-16open 3-14positions 3-26SFI 3-14temperature ranges 3-12types 3-12

Sample thermocoupledescription 4-7

Sampling interval in MDSC C-40

Index


Segments 3-22

Sensitivityincreasing with MDSC C-10

SFI sample pan 3-14

Shutting down 2-25

Signal deconvolutionwith MDSC C-17

Signal displayin MDSC C-39

Signal generationin MDSC C-17

Specific heat calculationsguidelines 4-13in MDSC C-43

Specificationsfor DSC 2920 CE 1-16for Standard DSC cell 1-17

Stand by (status code) 4-12

Standard DSC Cellatmosphere 1-17baseline noise 1-18cooling rate 1-17description 1-10sample pans 1-17sample size 1-17sample volume 1-17specifications 1-17

Starting up 2-23

Status codesexplanations 4-9

Subambient experiments 3-29

Subambient operationcell installations 2-20

T

TA Instrumentsaddresses B-1helplines x, B-2

Temp* (status code) 4-12

Temp°C (status code) 4-12

Temperaturein MDSC C-36

Temperature calibration 3-7

Thermal conductivityin MDSC C-69

operating parameters C-74

Thermal safety xvi

Thermocouplesdescription 4-7

Transitionscomplex

MDSC for C-9

Index


V

Vacuum fitting 2-12

Vacuum lineconnecting 2-13

W

WeightDSC 2920 CE 1-16dual sample DSC cell 1-19standard DSC cell 1-16

TA INSTRUMENTS CE PRESSURE CELL PDSC–1

Pressure DSC Cell


A SUBSIDIARY OF WATERS CORPORATION

109 Lukens Drive New Castle, DE 19720

DSC 2920 CEPressure Cell

DSC 2920 CE Operator’s ManualAppendix

(Please insert this document in the back ofyour DSC 2920 CE Manual)

PN 825605.002 Rev. BIssued July 2000

Appendix

PDSC–2 TA INSTRUMENTS CE PRESSURE CELL

© 1997, 2000 by TA Instruments109 Lukens DriveNew Castle, DE 19720

Notice

The material contained in this manual is believedadequate for the intended use of this instrument.If the instrument or procedures are used forpurposes other than those specified herein,confirmation of their suitability must be obtainedfrom TA Instruments. Otherwise, TA Instru-ments does not guarantee any results andassumes no obligation or liability. This publica-tion is not a license to operate under or arecommendation to infringe upon any processpatents.

TA Instruments Operating Software and Instru-ment, Data Analysis, and Utility Software andtheir associated manuals are proprietary andcopyrighted by TA Instruments, Inc. Purchasersare granted a license to use these softwareprograms on the instrument and controller withwhich they were purchased. These programsmay not be duplicated by the purchaser withoutthe prior written consent of TA Instruments.Each licensed program shall remain the exclusiveproperty of TA Instruments, and no rights orlicenses are granted to the purchaser other thanas specified above.


Pressure DSC Cell

Table of ContentsNotes, Cautions, and Warnings ................... 5

Helplines ...................................................... 6

To TA Instruments ...................................6

Safety .......................................................... 7

CE Compliance ........................................7

Instrument Symbols .................................8

Introducing the Pressure DSC Cell ............. 9

Technical Description ............................ 10

Specifications ......................................... 11

Installing the Pressure DSC Cell .............. 12

Pressure Calibration .................................. 16

Important Safety Information .................... 17

Running a Pressure DSC Experiment ....... 19

Experimental Procedure ........................ 19

Loading a PressureDSC Sample .......................................... 20

Lapping the Silver Lid and Ring ......... 22

Appendix


Replacing the Gasin the PDSC Cell ................................... 24

By Displacement ................................ 24

By Evacuation .................................... 25

Controlling Cell Pressure ....................... 26

Operation at Constant Volume ........... 26

Operation at Constant Pressure ......... 27

Operation with Dynamic Pressure(Fixed Purge Rate) ............................. 28

Releasing Cell Pressure...................... 30

Operating Under Vacuum ...................... 30

Maintenance and Diagnostics ................... 31

Replacement Parts .................................... 32

Index ......................................................... 33


Pressure DSC Cell


This manual uses NOTES, CAUTIONS, andWARNINGS to emphasize important and criticalinstructions.

A WARNING indicates a procedure that maybe hazardous to the operator or to theenvironment if not followed correctly.



!WARNING

u CAUTION:

NOTE:

Appendix


Helplines

To TA Instruments

For Technical Assistance......... (302) 427-4070

To Order Instruments andSupplies .................................... (302) 427-4040

For Service Inquiries ................ (302) 427-4050

Sales ......................................... (302) 427-4000


Pressure DSC Cell

SafetyThis equipment has been designed to complywith the following standards on safety:� IEC 1010-1/1990 + A1/1992 + A2/1995� IEC 1010-2-010/1992 + A1/1996� EN 61010-1/1993 + A2/1995� EN 61010-2-010/1994� UL 3101-1, First Edition.

CE Compliance

In order to comply with the ElectromagneticCompatibility standards of the European CouncilDirective 89/336/EEC (EMC Directive) andDirective 73/23/EEC on safety as amended by93/68/EEC, the following specifications apply tothe DSC 2920 CE instrument:

� Safety:EN 61010-1/1993 + A2/1995 InstallationCategory IIEN 61010-2-010/1994

� Emissions:EN 55022: 1995, Class B (30�1000 MHz)radiatedEN 55022: 1995, Class B (0.15�30 MHz)conducted

� Immunity:EN 50082-1: 1992 ElectromagneticCompatibility�Generic immunity standardPart 1. Residential, commercial, and light

industry.� IEC 801-2: 1991, 8 kV air discharge.� IEC 801-2: 27�500MHz, 3V/m. No

response above 80 mW (400 nV) heatflow (DEt) and 2.0°C sample

temperature.� IEC 801-4: 1988 Fast transients com-

mon mode 1kV AC power.

Appendix


Safety(continued)

Instrument Symbols

The following labels are displayed on the Pres-sure DSC (PDSC) Cell for your protection:

Symbol Explanation

This symbol, whichappears on the cell powerconnector on the instru-ment, indicates thathazardous voltage may bepresent on this connector.

This symbol, whichappears on the pressurecylinder and top plate ofthe PDSC Cell, indicatesthat the parts marked,including the thumbscrewbolts, may be hot. Takecare not to touch theseareas or allow anymaterial that may melt orburn to come in contactwith these hot surfaces.

Please heed the warning labels and take thenecessary precautions when dealing with thoseparts of the instrument.

For all other safety items, see the DSC 2920 CEOperator's Manual.


Pressure DSC Cell

Introducing thePressure DSC Cell

The Pressure DSC (PDSC) cell (FigurePDSC.1) is a DSC cell enclosed in a steelcylinder that can be pressurized to 7 MPa (1000psi). In addition to performing the same mea-surements as the DSC cells, it can operate atelevated pressure or under vacuum. This abilityto vary pressure as well as temperature providesthe following:

� Resolution of overlapping peaks� Determination of heats of vaporization and

vapor pressure� Reaction rates in controlled atmospheres� Studies of pressure-sensitive reactions� Storage of cell pressure in the data file.

The Pressure DSC cell has two gas flow controlvalves, a three-way valve, a pressure gauge, apressure release valve, and gas pressure fittingson the side. An 8.3 MPa (1200 psi) pressurerelief valve and a pressure transducer arecontained in the base of the cell.

Figure PDSC.1Pressure DSC Cell

Appendix


Technical Description

Like the standard and dual sample DSC cells,the Pressure DSC Cell uses a constantan(thermoelectric) disc as a primary heat-transferelement. A silver heating block, capped with avented silver lid, encloses the constantan disc.The selected sample(s) and an inert referenceare placed in pans that sit on raised portions ofthe disc. Heat is transferred through the con-stantan disc to both the sample(s) and thereference pans. Differential heat flow to thesample(s) and reference are monitored by thechromel-constantan area thermocouples. Thethermocouples are formed at the junctions of theconstantan disc and the chromel wafers weldedto the underside of the two raised portions of thedisc. Chromel and alumel wires are connected tothe chromel wafers at the thermocouple junc-tions to measure sample temperature. Thealumel wire welded to the reference wafer is forthermal balance.

Purge gas, entering the heating block through aninlet in the Pressure DSC cell�s base plate, ispreheated to block temperature by circulationbefore entering the sample chamber through thepurge gas inlet. Gas exits through the vent hole inthe silver lid.

Vacuum and air cooling ports on the DSC 2920CE lead to openings in the cell but not directly tothe sample chamber.


Pressure DSC Cell

Table PDSC.1Pressure DSC CellSpecifications

Specifications

Dimensions Depth 27.2 cm (10.7 in.)Width 22.8 cm (9.0 in.)Height 31.2 cm (12.3 in.)

Weight(approx.) 11.5 kg (25 lb)

Temperature Room temperature torange 725°C

Atmosphere 1.3 Pa to 7 MPa, constantpressure or constant

volume

Dynamic gaspurge To 200 mL/min

Baseline noise + 10 µW

Other specifications are similar to those ofthe standard DSC Cell. Performancedepends on the pressure and atmosphereselected.

Appendix


Installing thePressure DSC Cell

To install the Pressure DSC (PDSC) Cell on theDSC 2920 CE, follow these instructions andrefer to Figures PDSC.2, PDSC.3, and PDSC.4.

Do not remove the white, fibrous insulation frominside the cell cover. Refer to the MSDS sheetsupplied with the Pressure Cell for the neces-sary precautions.

1. Hold the PDSC as shown in Figure PDSC.2,and slide it onto the baseplate following thealignment guides. The back of the cellshould touch the connector housing on theDSC 2920 CE.

Figure PDSC.2Installing thePDSC Cell

t CAUTION:


Pressure DSC Cell

When the cell is fully mated with the connectors,you will see the following message displayed:


Then this message will be displayed:

Contact complete.DSC Pressure.

The display then returns to normal.

2. Push down on the two hold-down thumb-screws (see Figure PDSC.3) and turn themclockwise. The hold-down screws need onlybe finger tight to engage the safety interlockand keep the PDSC stable.

Figure PDSC.3The Pressure DSC Cell

PRESSURECYLINDER

THUMBSCREWBOLT

CONSTANTANDISC

HOLD-DOWNTHUMBSCREWS

OUTCONTROLVALVE

INCONTROLVALVE

PRESSURECOVER

O-RINGSEAL

TOP PLATE

COVER

SILVER LID

FILL/PURGEVALVE

PRESSUREGAUGE

Appendix


Tightening down the hold-down thumbscrewsengages a power interlock in the instrumentbase. No power is supplied to the cell withoutthem. They must be in place to run the instru-ment.

3. Connect a sufficient length of 0.32-mm(0.125-inch) tubing from a pressure regulatoron your pressurized gas source to the INport on the side of the PDSC Cell (seeFigure PDSC.4). The gas (nitrogen, air,oxygen, etc.) should be pressure-regulatedup to 7 MPa (1000 psi).

Figure PDSC.4Side View of thePressure DSC

t CAUTION:


Pressure DSC Cell

If oxygen is used, be certain to use fittings,gauges, and tubing that are oxygen-rated.

The regulator you choose should have twogauges: one to monitor source pressure and oneto monitor the regulator output pressure. Theregulator should be rated to withstand the sourcepressure; its output should cover the experi-mental range up to 7 MPa (1000 psi).

DO NOT connect the PDSC directly to apressurized gas source without using anappropriate regulator.

The tubing must be of sufficient strength towithstand the pressure to be used in yourexperiments.

t CAUTION:

!WARNING

!WARNING

Appendix


Pressure CalibrationPressure calibration is an optional calibrationprocedure for the pressure DSC cells. It is basedon comparing the pressure reading at two points,typically 1 atmosphere and another pressureselected by you, to the pressure reading on anexternal pressure gauge. See the online docu-mentation with your instrument control softwarefor information.


Pressure DSC Cell

Important Safety Information

Please read this before using oxygen in thePressure DSC Cell

If excessive amounts of hydrocarbons arepresent in the Pressure DSC (PDSC), energeticcombustion could occur causing damage to thePressure DSC cell and possible injury to theoperator. To help prevent these problems,follow these guidelines:

(1) Clean Supply Lines: The oxygen supplylines, valves, gauges, and regulators must allbe free of hydrocarbons and rated for oxygenservice. Check with your supplier if you areuncertain whether a component is rated foroxygen service. If the inside of the tubingsmells “oily” or has liquid or a black carbonresidue in it, hydrocarbons may be present.Consult with your compressed gas suppliersfor a cleaning procedure.

(2) Cell Contamination: Remove the pressurehousing and visually inspect the Pressure DSCcell for oil or other organic contamination.The entire oxygen pressure system must befree of hydrocarbons. If there is a possibilityof hydrocarbon contamination (spilled samples,oily residue, oily smell, carbon black, etc.) inyour Pressure DSC cell, immediately discon-tinue use. Contact TA Instruments Service at(302) 427-4050 to schedule a safety inspec-tion, or for additional information.

!WARNING

Appendix


Check all Supply Tubing. All tubing connectingyour Pressure DSC cell to other devices(oxygen cylinder, gauges, valves, regulators,etc.) should be 3.2 mm (1/8-inch) o.d. Allplumbing, valves, gauges, and regulators mustbe rated for high pressure service to21 MPa (3000 psig) and be free ofhydrocarbons.

You should review the warnings on the previouspage if you plan to use oxygen in the PDSC andany of the following conditions apply to you.

q New installation of a PDSCq Modification of supply lines, valves or

gaugesq Sample was spilled in the PDSCq PDSC has an �oily� smellq PDSC has not been used recently.

You may insure safe operation of your PressureDSC if you follow the important safety instruc-tions and warnings as directed throughout thissection and the entire manual.

!WARNING


Pressure DSC Cell

Running a PressureDSC Experiment

Any time you open the OUT or pressure-releasevalve during operation, you may be applyingfull pressure to the external lines or compo-nents (e.g., flowmeter), which may not be ableto withstand full pressure. If you have avacuum connected to the cell, the pressurewould be reversed back into the cell, whichmay not be able to withstand an abruptchange in pressure. This could seriouslydamage the cell.

Keep the Pressure DSC Cell away from flam-mable materials.


Pressure DSC experiments involve the sameprocedures as DSC experiments, with thefollowing exceptions:

� Loading the sample(s)� Purging the cell� Controlling cell pressure� Operating under vacuum.

!WARNING

!WARNING

Appendix


Loading aPressureDSC Sample

Once you have prepared the sample pan andentered all necessary pre-experiment data (asexplained in Chapter 3 of the DSC 2920 CEOperator's Manual), you are ready to load thesample pan into the PDSC Cell. The PDSC Cellshould already be installed on the DSC 2920 CEbefore you load the sample (see page PDSC-12for installation instructions).

1. Close the IN control valve (see FigurePDSC.5) to shut off the gas supply to thecell.

2. Slowly open the pressure-release valve, andleave it open to ensure that the cell is atambient pressure.

Figure PDSC.5Pressure DSCCell Controls

FRONT VIEW

SIDE VIEW


Pressure DSC Cell

THUMBSCREWBOLT

PRESSURECYLINDER

HOLD-DOWNTHUMBSCREWS

CONSTANTANDISC

COVERSILVER LID

FILL/PURGEVALVE

PRESSUREGAUGE

PRESSURECOVER

O-RINGSEAL

OUTCONTROLVALVE

INCONTROLVALVE

TOP PLATE

!WARNING

3. Unscrew the three thumbscrew bolts (FigurePDSC.6) from the top plate. Do not usetools to open or close the cell.

If you have difficulty unscrewing the thumb-screw bolts (excessive bolt friction), you can bealmost certain that the cell is still under somepressure. Recheck the valve positions asdescribed in steps 1 and 2.

Figure PDSC.6Pressure DSC Cell

Appendix


4. Remove the top plate, cell cover, and silverlid.

If the cell has just been used, these compo-nents could be very hot. As a safe operatingpractice, use leather gloves when handling thetop plate, and use tweezers whenever handlingthe metal cell cover or silver lid.

5. Load the sample and reference pans as youwould for a standard cell.

6. Replace the silver lid, cell cover, and topplate. Push the top plate down as far as itwill go, taking care not to damage the O-ringor jar the cell, which could cause the pans tomove off the dimples.

7. Uniformly finger-tighten the three thumb-screw bolts, making certain that the threadsare fully engaged.

Lapping the Silver Lid and Ring

If sinusoidal baseline noise is observed in aPDSC thermal curve obtained under pressure,the silver lid and gas ring (the silver ledge onwhich the lid sits) may have become slightlywarped and should be smoothed out with thelapping tool before the next run. The lapping toolis provided with the PDSC Cell.

1. Place the silver lid, handle side up, on a pieceof fine-grit emery paper backed by a flat,smooth surface, and move the lid in a figure-eight motion until any deformed areas aresmoothed.

!WARNING


Pressure DSC Cell

2. To smooth the gas ring, attach a piece ofabrasive paper (400 grit) to the lapping toolwith the double-sided tape provided. Trimthe paper to the size of the tool using scis-sors or a razor knife. Rotate the lapping tool(PN 008837.001) back and forth on the ringwith light-to-moderate pressure. Cleanafterward with a fiberglass brush and a lightair blast.

Be sure to wear safety glasses or goggles whencleaning the cell with air.

3. Make sure that you are using the current2920 CE PDSC silver lid (PN 900969.001).It has a smaller purge hole than previousversions; it is thicker; and it has a ridgearound the bottom. These features all aid inremoving the sinusoidal baseline noise.

NOTE:

Appendix


Replacing the Gasin the PDSC Cell

If you wish to replace the gas in the PDSC Cellbefore your experiment, follow the guidelines inthis section. Two ways to perform gas replace-ment are presented here�displacement of thecurrent gas and evacuation of the gas present.Dynamic gas replacement during the experimentis explained under �Controlling Cell Pressure,�on page PDSC-26.

By Displacement1. Close the IN control valve.

2. Close the OUT control valve.

3. Set the PURGE/FILL valve to fill.

4. Set the output regulator on the source gascylinder to the maximum initial pressure ofthe experiment. If the cell is to be operatedat constant volume, do not exceed 7 MPa(1000 psi).

5. Slowly open the IN control valve, and allowgas to fill the cell to about 2 MPa (300 psi).

6. Close the IN control valve, then open thepressure-release valve and allow the pres-sure to return to ambient.

7. Close the pressure-release valve.

8. Repeat steps 5 through 7 two times.


Pressure DSC Cell

9. Open the IN valve, and allow the pressure tobuild to the desired level.

By Evacuation1. Attach a vacuum pump and hose to the

pressure-release valve outlet. Insert a gaugefor measuring pump head pressure into thehose using a tee fitting.

2. Close all three valves on the cell: OUT, IN,and pressure-release.

3. Set the PURGE/FILL valve to fill.

4. Start the vacuum pump and open the pres-sure-release valve. Then slowly open the INvalve to introduce source gas into the cell.Monitor the head pressure of the vacuumpump while the gas flows through the cell.Adjust this pressure with the IN valve. Donot allow the head pressure to exceed themanufacturer�s limits for the pump.

5. Allow the gas to flow through the cell forseveral minutes.

6. Close the pressure-release valve first, thenshut off the vacuum pump and open the INvalve, allowing the pressure to build to thedesired level.

Appendix


ControllingCell Pressure

Before you begin your experiment, make sureyou have charged up the Pressure DSC Cell tothe pressure required for your experiment.Guidelines for operation at constant volume,constant pressure, and dynamic pressure aregiven here. As you perform experiments, thepressure will be stored in the data file.

During an experiment, if the pressure transducerindicates a pressure greater than 7.7 MPa, theexperiment will be terminated.

Operation atConstant Volume

After replacing the gas, check that all three cellvalves are closed, that the cell is at some positivepressure, and the PURGE/FILL valve is set topurge. Use the cell pressure shown on theinstrument display to determine the internalpressure of the cell.

If the cell pressure is lower than the desiredstarting pressure, use the IN valve to raise it. Ifthe cell pressure is too high, use the OUT valveto lower it. However, use the IN and OUTvalves conservatively; there is a lag in thereading of any pressure gauge, and if the valvesare opened too rapidly or too far, the finalpressure will overshoot or undershoot the desiredstarting pressure.

The maximum permissible starting pressure forconstant volume operation is 7 MPa (1000psi) at room temperature. DO NOT exceed thisvalue.

NOTE:

!WARNING


Pressure DSC Cell

Operation atConstant Pressure

For work at constant pressure, a flowmeter isrequired at the OUT valve to allow bleed-off ofexcess pressure.

After gas replacement, ensure that all three cellvalves are closed and the cell is at some positivepressure with the PURGE/FILL valve set to fill.

1. Set the source gas regulator slightly abovethe desired operating pressure.

2. Check the connections of the flowmeter atthe OUT fitting on the cell. Close the OUTvalve.

3. Slowly open the IN valve on the cell. Waitfor the internal cell pressure, as indicated onthe instrument display, to stabilize at somepoint slightly above the desired operatingpressure.

4. Slowly open the OUT valve.

5. Set an unrestricted flowmeter to 1 L/min.Gas should vent from the cell. Wait for theinternal cell pressure to stabilize at thedesired operating pressure.

6. Turn the PURGE/FILL valve to purge.

Appendix


Operation withDynamic Pressure(Fixed Purge Rate)

After gas replacement, ensure that all three cellvalves are closed, that the cell is at some positivepressure, and that the PURGE/FILL valve is setto fill. Dynamic pressure operation is equivalentto operation at constant flow. An unrestrictedflowmeter is required at the OUT fitting foroperation in this mode.

1. Set the regulator at the source gas cylinderto an appropriate pressure.

2. Slowly open the IN valve.

3. Slowly open the OUT valve. Wait for theflow measured at the flowmeter to stabilize.If finer flow adjustment is desired, a meter-ing flow valve may be connected betweenthe OUT port and the flowmeter.

4. Adjust the OUT valve until the flowmeterindicates the desired value. If the flow rate istoo low with the OUT valve fully opened,check the position of the IN valve. Carefullyopen the IN valve further if necessary. Ifthis does not raise the flow to the desiredrate, the source gas pressure must beadjusted.

Do not adjust the regulator at the pressurecylinder while the valves are open. A surge maydamage the cell.

t CAUTION:


Pressure DSC Cell

5. To readjust the source gas pressure, close allthree valves, then repeat this procedure fromstep 1.

6. Wait until the pressure and flow rate are atthe desired values. Turn the PURGE/FILLvalve to purge.

Because a flowmeter in this position is venting tothe atmosphere, be sure to take the pressuredifferential into account when calculating flowrate over the sample at an elevated pressure.Configured in this manner, the purge gas willpass through the heating block and enter directlyinto the sample chamber. This allows the purgegas to be preheated before it contacts the sampleand also sweeps any sample volatiles or decom-position gases out of the sample chamberthrough the silver lid.

Do not place any restrictions in the line fromthe flowmeter. A restricted line will cause theflowmeter to become pressurized.

The upper operating temperature for the Pres-sure DSC Cell is limited by heating rate, purgegas thermal conductivity, and test pressure.

!WARNING

Appendix


ReleasingCell Pressure

After a PDSC run is complete, slowly releasethe cell pressure by opening the pressure-releasevalve.

The exhaust gas from the pressure-releasevalve may be hot enough to cause burns, fires,or damage to materials.

Rapid release of pressure can cause damage to thecell.

OperatingUnder Vacuum

To operate the Pressure DSC under vacuum,connect a vacuum system to the pressure-release valve, and leave the two other valvesclosed. Procedures for cell loading and operationare the same as for the standard DSC cell.

To maintain normal sensitivity and resolutionunder vacuum, you may need to use a thermallyconductive material (preferably a paste) betweenthe constantan disc and the pans. Silicone heat-sink greases (Dow Corning type 340 orequivalent) work very well. Silicone high-vacuumgreases may also be used. These should not beused at temperatures over 200oC.

t CAUTION:

!WARNING


Pressure DSC Cell

Maintenance and DiagnosticsDiagnosis of power problems and test functions,cleaning, and maintenance of the DSC 2920 CEPressure Cell are similar to those for the stan-dard DSC cell. See Chapter 5 of the DSC 2920CE Operator's Manual for this information andthe procedures.

Appendix


ReplacementParts

Table PDSC.2Replacement Partsfor Pressure DSC Cell Part Number Description

202813.039 1 O-ring, PDSCPressure Cylinder Seal

008837.001 1 gas ring lapping tool

900969.002 Silver PDSC lid (flat)

900601.901 PDSC insulation, pkg 6

Pressure DSC Cell

TA INSTRUMENTS CE PRESSURE CELL PDSC-33

Index

B

baseline noisecause 22

C

calibrationpressure 16

CE compliance information 7

cell pressurecontrolling 26releasing 30

constant pressure operation 27

constant volume operation 26

controlson PDSC 20

D

diagnostics 31

dynamic pressure operation 28

E

experiment(s)baseline noise 22controlling cell pressure 26lapping silver lid and ring 22loading a sample 20procedure 19releasing pressure 30replacing gas for 24running 19

F

features of PDSC 9

fixed purge rate operation 28

G

gas displacement 24

gas evacuation 25

gas replacement in PDSC 24

H

Helplines to TA Instruments 6

Appendix

PDSC-34 TA INSTRUMENTS CE PRESSURE CELL

I

installing the PDSC 12

L

labels on instrument 8

lapping tool for PDSC 22

M

maintenance 31

P

parts list 32

parts of PDSC 9

pressurecontrolling 26releasing 30

pressure calibration 16

R

replacements parts for PDSC 32

S

safety 7CE specifications 7instrument labels 8standards 7

sample(s)loading 20

specifications for PDSC 11

T

technical description of PDSC 10

V

vacuum operation 30

TA INSTRUMENTS CE DTA CELL DTA-1

DSC 2920 CE1600°C DTA

Cell

DSC 2920 CE Operator�s Manual

Appendix

(Please insert this document in the back of

your DSC 2920 CE Manual)

PN 825606.002 Rev. A

Issued June 1997


A SUBSIDIARY OF WATERS CORPORATION

109 Lukens Drive New Castle, DE 19720

Appendix

DTA-2 TA INSTRUMENTS CE DTA CELL

© 1997 by TA Instruments109 Lukens DriveNew Castle, DE 19720

Notice

The material contained in this manual is be-lieved adequate for the intended use of thisinstrument. If the instrument or procedures areused for purposes other than those specifiedherein, confirmation of their suitability must beobtained from TA Instruments. Otherwise, TAInstruments does not guarantee any results andassumes no obligation or liability. This publica-tion is not a license to operate under or arecommendation to infringe upon any processpatents.

TA Instruments Operating Software and Instru-ment, Data Analysis, and Utility Software andtheir associated manuals are proprietary andcopyrighted by TA Instruments, Inc. Purchasersare granted a license to use these softwareprograms on the instrument and controller withwhich they were purchased. These programsmay not be duplicated by the purchaser withoutthe prior written consent of TA Instruments.Each licensed program shall remain the exclu-sive property of TA Instruments, and no rightsor licenses are granted to the purchaser otherthan as specified above.


Table of Contents

Notes, Cautions, and Warnings .................... 5

Helplines ....................................................... 6

Safety ............................................................ 7

CE Compliance ...................................... 7

Warning Label ........................................ 8

Introducing the CE 1600° Cell ..................... 9

Specifications ....................................... 10

Technical Description ................................. 11

DTA Sample and ReferenceThermocouple Assembly................... 11

DTA Sampling System......................... 12

Principles of Operation ............................... 13

Installing the CE 1600°C DTA Cell ........... 14

Installing the Furnace Tube .................. 16

Installing the ThermocoupleAssembly ........................................... 18

Installing the Cell ................................. 23

Aligning the DTA Cell Furnace ........... 26

Appendix



Running a 1600°C DTA Experiment........... 31

Experimental Procedure ........................ 31

Preparing Samples................................. 32

Selecting Sample Cupsand Liners................................. 32

Loading the Sample............................... 33

Purging the CE 1600°C DTA Cell ........ 36

Stopping an Experiment ........................ 38

Replacement Parts ....................................... 39

Ordering Information ................................... 40

Index ............................................................ I-1



This manual uses NOTES, CAUTIONS, andWARNINGS to emphasize important andcritical instructions.



A WARNING indicates a procedure that maybe hazardous to the operator or to theenvironment i f not fol lowed correctly .

!!!!!WARNING

uuuuu CAUTION:

NOTE:

Notes, Cautions, and Warnings

Appendix


Helplines

To TA Instruments

For Technical Assistance ........ (302) 427-4070

To Order Instruments andSupplies .................................. (302) 427-4040

For Service Inquiries............... (302) 427-4050

Sales ........................................ (302) 427-4000


SafetyThis equipment has been designed to complywith the following standards on safety:• IEC 1010-1/1990 + A1/1992 + A2/1995• IEC 1010-2-010/1992 + A1/1996• EN 61010-1/1993 + A2/1995• EN 61010-2-010/1994• UL 3101-1, First Edition.

CE ComplianceIn order to comply with the ElectromagneticCompatibility standards of the European Coun-cil Directive 89/336/EEC (EMC Directive) andDirective 73/23/EEC on safety as amended by93/68/EEC, the following specifications apply tothe CE 1600°C DTA cell.

• Safety:EN 61010-1/1993 + A2/1995 InstallationCategory IIEN 61010-2-010/1994

• Emissions:

EN 55022: 1995, Class B (30–1000 MHz)radiatedEN 55022: 1995, Class B (0.15–30 MHz)conducted

• Immunity:

EN 50082-1: 1992 ElectromagneticCompatibility—Generic immunity standardPart 1. Residential, commercial, and light

industry.— IEC 801-2: 1991, 8 kV air discharge.— IEC 801-3: 27–500MHz, 3V/m. No

response above 0.062°C@600°C(750 nV) ∆T.

— IEC 801-4: 1988 Fast transients com-mon mode 1kV AC power.

Safety

Appendix


Safety(continued)

Warning Label

The following label is displayed on the CE1600°C DTA Cell for your protection:

Symbol Explanation

This label, displayed onfront of the furnace,indicates that a hotsurface may be present.Take care not to touchthis area or to allow anymaterial that may melt orburn to come in contactwith this hot surface.

Please heed the warning label and take thenecessary precautions when dealing with thispart of the instrument.

For all other safety items, see the DSC 2920 CEOperator's Manual.


Introducing the CE1600°C DTA Cell

The CE 1600°C DTA Cell (Figure DTA.1) isused to determine the temperatures of heat-related transitions at high temperatures. Thesample and reference materials are placed incups that sit on the tops of two thermocouplepedestals within the furnace tube of the 1600°Cfurnace. The thermocouples measure both thepresence of transitions and the temperatures atwhich they occur.

Figure DTA.1The CE 1600°C DTA Cell

Introducing the 1600°C DTA Cell

Appendix


Table DTA.1Specificationsfor CE 1600°CDTA Cell

!!!!!WARNING

Specifications

Dimensions Depth 24.1 cm (9.5 in.)Length 29.7 cm (11.7 in.)Height 14.2 cm (5.6 in.)

Weight (approx.) 4.83 kg (10.5 lbs)

Temperature Ambient to 1600oCrange

∆T sensitivity 0.001oC

Sample size Up to 75 mm3

Sample cups Platinum micro (3 mm ID)Platinum macro (5 mm ID)Alumina micro (3 mm ID)

Sample and Platinum-platinum/13%reference rhodium Type Rthermocouples

Control Platinum-platinum/13%thermocouple rhodium Type R

Atmosphere Static or controlled flowwith inert or reactive gasor air

Purge gases Recommended: air, argon,helium, nitrogen, or oxygen

Do not use hydrogen or anyother explosive gas with theDSC 2920 CE.

Pressure Atmospheric to 266 Pa(2 torr)

Temperatureprecision ±2oC



The CE 1600oC DTA Cell consists of a 1600oCfurnace and furnace base, a furnace tube, asample and reference thermocouple assembly,and sample cups.

The DTA furnace assembly is a low-mass, plug-in unit that is insulated and shielded for efficientheating.

The furnace winding is a platinum alloy. Thecontrol thermocouple is platinum-platinum/13%rhodium and is positioned directly in thesidewall in a ceramic sheath.

DTA Sampleand ReferenceThermocoupleAssembly

The CE 1600oC DTA thermocouple assemblyconsists of a matched pair of platinum-platinum/13% rhodium thermocouples inserted in ceramictubes, a ceramic center post, and a spring clipthat holds the ceramic tubes. The height of thethermocouples is critical. You can adjust theheight of the thermocouples by removing thespring clip and sliding the ceramic tubes up ordown the post. The thermocouple leads extendthrough the retainer and out the hole in the DTAfurnace base, and then plug into a PC board.


Appendix


DTA Sampling System

Macrocups are provided with the DTA cell ondelivery. Both platinum and alumina liners areprovided for the macrocups. The cups fit overthe ceramic tubes, which are machined down atthe ends to provide a shoulder. The macrocupswith liners are suitable for materials that melt orsinter. They also enable you to use large samplesfor increased sensitivity.


Principlesof Operation

Refer to Chapter 4 of the DSC 2920 CEOperator's Manual for principles of operationand applications information.

Although the CE 1600°C DTA differs in con-figuration from the DSC cells, particularly inhow the thermocouples sense the sample andreference temperatures, as well as in usingplatinum-platinum/13% rhodium (type R)thermocouples, similar principles apply to itsoperation. The differential voltage between thethermocouples at the sample and referenceplatforms is linearized/converted to °C for theDTA by the Seebeck coefficients (see referenceNBS Monograph 125).


Appendix


Installing the CE 1600°C DTA Cell

Before you install your CE 1600°C DTA Cell(Figure DTA.2), check the accessory kit thatcame with the cell to ensure that it contains thefollowing items:

• 1 adapter, 90-degree bend standard• 1 spatula, style B• 1 package of platinum liners• 1 package of alumina liners• 1 package of macro cups• 1 aluminum oxide sample (with Material

Safety Data Sheet)• 1 9/64-inch hex wrench (modified)• 1 furnace alignment tool• 1 furnace tube• 1 3/32-inch hex wrench (modified)• 2 thumbscrews• 1 silver crystal sample (with Material Safety

Data Sheet).

Installation of the CE 1600oC DTA Cell consistsof these four steps, which are detailed in thepages that follow:

(1) Installing the furnace tube(2) Installing the thermocouple assembly(3) Installing the cell on the DSC 2920(4) Aligning the cell furnace.

You should become familiar with the cellfurnace alignment procedure before you attemptto run experiments with the DTA Cell.


Figure DTA.2Parts of the CE1600oC DTA Cell

FURNACEASSEMBLYTHUMBSCREW

FURNACE ASSEMBLY

HOLD-DOWNSCREWS

BELL JARLOCKINGNUT

SHIELDING DOORSFURNACECONNECTOR

CONNECTORCOVER

THERMOCOUPLESUPPORT

KNURLEDNUT

BASE

KNOB

SAMPLETHERMOCOUPLE

REFERENCETHERMOCOUPLE

Installing the 1600°C DTA Cell

Appendix

DTA�16 TA Instruments CE DTA Cell

FURNACETUBE

ADJUSTMENTSCREWS

FURNACE

Installing the Furnace Tube

After you have unpacked all the parts of yourDTA cell, the first step in putting it together isto install the furnace tube. Place the DTA cell ona stable surface, and perform these steps:

1. Loosen the two furnace assembly thumb-screws, located on either side of the furnaceassembly (see Figure DTA.3), and then liftthe furnace off the cell.


2. Loosen the knurled knob on the shieldingdoors, and open the doors.

3. Remove the DTA bell jar from the cell.

FURNACEBASE

SHIELDINGDOORS

SHIELDINGDOOR KNOB

FURNACEASSEMBLYTHUMBSCREW

TA Instruments CE DTA Cell DTA�17

4. Slide the furnace tube carefully into theopening on the top of the bell jar (see figurebelow), and firmly seat it.

Figure DTA.4Bell Jar and Furnace Tube

5. Tighten the bell jar locking nut with anAllen wrench. Set the bell jar and furnacetube assembly to one side while you proceedwith the installation of the thermocouple andcell.

LOCKINGNUT

OPENING FORFURNACE TUBE

FURNACETUBE


Appendix


Installing theThermocouple Assembly

The CE 1600°C DTA Cell thermocouple assembly isthe cell�s temperature sensor. It consists of amatched pair of platinum-platinum/13% rhodiumthermocouples mounted in a ceramic post.Because of its fragility, the thermocouple assemblyis packaged separately from the cell and must beinstalled by the operator.

1. Remove the thermocouple assembly (FigureDTA.5) from its plastic shipping containerand check it for damage. If the assembly isdamaged, notify TA Instruments immedi-ately.

Figure DTA.5DTA Thermocouple Assembly

2. Using a knife or razor blade, carefully cutand remove the heat-shrink tubing from thethermocouple assembly.

NOTE:

SHIPPING CONTAINER

CAP

SLIT

HEAT-SHRINKTUBING


3. Carefully lift the slitted bottom edges of theplastic cap to loosen it from the ceramicpost, and slide the cap off the post.

4. Remove the knurled nut from the thermo-couple support, and insert the thermocouplewires through the hole in the knurled nut(see Figure DTA.6).

5. Carefully insert the thermocouple assembly(with the knurled nut), wire-lead end first,into the thermocouple support, slipping thewire leads through the slot in the support(see Figure DTA.6).

Figure DTA.6Installing the Thermocouple

CERAMIC POST

SPRING CLIP

KNURLED NUT

THERMOCOUPLESUPPORT

CONNECTORCOVER


Appendix


6. Rotate the assembly so that the head of thespring clip on the ceramic post faces towardyou.

7. Gently push the thermocouple down until itwill go no further. Lock the post in positionby tightening the knurled nut.

The thermocouple distance is set at TA Instru-ments before shipment. Use Figure DTA.7 as aguide if you should need to reset the thermocoupledistance.

Figure DTA.7Guidelines toAdjust theThermocoupleDistance

Thermocouple Beads

Sample

WhiteCeramic Tubes

PostKnurled Nut

Spring Clip

Topof BaseAssembly

Ceramic Post

NOTE:

Reference


8. Pull off the connector cover by lifting oneside, then the other (see Figure DTA.6).Using long-nosed pliers, plug the ther-mocouple wires into the PC board, as shownin Figure DTA.8. Plug the correct coloredwires into their indicated position on the PCboard, making sure the wires do not getcrossed. The left and right thermocouplewires must plug into the left and rightpositions respectively.

Figure DTA.8Plugging inthe DTAThermocoupleWires


Appendix


9. Replace the connector cover, making surethat the wires are not pinched under theedges of the cover. The wires should pro-trude out of the slot in the back of the cover,as shown in Figure DTA.9.

Figure DTA.9ThermocoupleWires and theConnector Cover

10. Gently lower the furnace tube and bell jarassembly over the thermocouple, taking carenot to damage the thermocouple.

11. Close the shielding doors, and turn the doorknob 1/4-turn clockwise, until it engages inthe post behind it and shuts the doors firmly.

Now you are ready to install the DTA cell ontothe instrument.


Installingthe Cell

Refer to Figures DTA.2, DTA.3, DTA.10, andDTA.11 while installing the CE 1600oC DTACell with the furnace tube in place.

1. Slowly lower the furnace over the furnacetube and, using the guide pins on the furnacebase, seat the furnace on the furnace base(see Figure DTA.10).

If the furnace assembly does not slide easily overthe furnace tube, call your TA Instrumentsservice representative. Do not force the furnaceassembly over the furnace tube.

Figure DTA.10Installing the DTA Furnace Assembly

ttttt CAUTION:


Appendix


2. Firmly and evenly tighten the two furnaceassembly thumbscrews. Ensure that theassembly is tightly secured and does notwobble on the furnace base.

3. Slide the DTA cell onto the DSC 2920 CE,following the alignment guides on theinstrument until the connectors are firmlyplugged in (see Figure DTA.11). When thecell is fully mated with the connectors, youwill see the following message on theinstrument's display:


Figure DTA.11Installing theDTA Cell ontothe InstrumentBase


Then the next message will appear:

Contact complete.DTA 1600°C Delta-T.

Finally, the display returns to normal.

4. Secure the cell base to the DSC 2920 byfirmly and evenly tightening the largerthumbscrews supplied with the DTA Cell.

Do not use the thumbscrews that come with theDSC Cell.

ttttt CAUTION:


Appendix


Aligning theDTA Cell Furnace

After you install the CE 1600oC DTA cell forthe first time, you must align the cell furnacearound the furnace tube to ensure proper heatingand cell performance during experiments. If youlater remove and reinstall the DTA cell, thealignment should not be affected, but you maywish to check it as described in step 2 below.

Three adjustments to the furnace core arenecessary:

• Right-to-left adjustment• Front-to-rear adjustment• Angular adjustment (adjusting the angle of

the furnace core so that it is parallel to thefurnace tube).

You will need to use the calibration rod in theDTA Installation Kit to perform the alignment.A flashlight or other source of light is alsohelpful in determining the clearance between thecell furnace and furnace tube.


2. Center the furnace tube around the thermo-couple assembly, and tighten the lockingcollar firmly using the 3/32-inch hex wrenchshipped in the DTA accessory kit.


3. Look down through the top of the cell anddetermine whether the furnace tube isroughly in the center of the furnace. Clear-ance between the cell furnace and thefurnace tube must be the same all the wayaround and down its length.

4. If the furnace tube is not centered within thefurnace, turn the x and y screws (see FigureDTA.12) in the appropriate direction(according to Table DTA.2) to center thefurnace around the furnace tube.

Figure DTA.12Location of the Adjustment Screws

Y-ADJUSTMENTSCREW(FRONT/REAR)

Z-ADJUSTMENTSCREWS(FURNACEANGLE)

X-ADJUST-MENTSCREW(LEFT/RIGHT)


Appendix


Table DTA.2Using the x- andy-Adjustment Screws

Adjustment Direction Screw Turned* Effect

x-adjustment CW Moves thescrew furnace core

to the left.

CCW Moves thefurnace coreto the right.

y-adjustment CW Moves thescrew furnace core

away fromyou.

CCW Moves thefurnace coretoward you.

*CW = clockwise; CCW = counterclockwise

5. Place the calibration rod in the spacebetween the furnace core and the furnacetube. You should be able to move thecalibration rod up and down freely in thisspace.

Always move the calibration rod perpendicular tothe furnace base when you check the furnace coreand tube clearance. Do not pull the rod around thespace.

NOTE:


If the rod does not move freely, the furnace coreis not parallel to the furnace tube; clearancebetween the furnace core and the furnace tube isnot the same along the entire length of thecalibration rod. You need to adjust the angle ofthe furnace core, as explained in step 6.

6. Use the two z-adjustment screws (see FigureDTA.12) to correct the angle, or lean, of thefurnace core. Refer to Tables DTA.3 andDTA.4 to determine which screw to adjustand the direction it should be turned.

Adjustment Direction Screw Turned* Effect

Left z screw CCW Moves the leftside of thefurnace core up.

CW Moves the leftside of thefurnace coredown.

Right z screw CCW Moves the rightside of thefurnace core up.

CW Moves the rightside of thefurnace coredown.


Table DTA.3Using the z-AdjustmentScrews


Appendix


Table DTA.4Guidelines forz-AdjustmentScrews

Rod Move left Move rightsticks at: z screw: z screw:

12 o’clock CW CW

3 o’clock CW CCW

6 o’clock CCW CCW

9 o’clock CCW CW


Adjusting the z screws may affect the x and yadjustments already made. Whether you need toreadjust the x and y screws depends on howmuch the z screws were adjusted.

7. Continue with the following two-stepsequence until the calibration rod enters andleaves the space freely without touching:

a. If the rod touches, adjust the z screws asnecessary (see Tables DTA.3 andDTA.4).

b. Adjust the x and y screws if necessary.(Check using the short end of thecalibration rod, or determine visually.)

8. Close the shielding doors, and turn the doorknob 1/4-turn clockwise until it engages inthe post behind it and shuts the doors firmly.


Running a 1600°CDTA Experiment


1600°C DTA (Differential Thermal Analysis)experiments involve the same procedures asDSC experiments, with the following excep-tions:

• Preparing samples• Loading the sample• Purging the cell• Stopping the experiment.

The COOLING GAS line is not operational when aDTA cell is installed. The Switch Air Cool functionand the Air Cool option are not available.


NOTE:

Running a 1600°C DTA Experiment

Appendix


Preparing Samples

Selecting SampleCups and Liners

Platinum sample cups are available for the1600°C DTA as macrocups (5 mm I.D., volume75 µL). The macrocups, which are used withliners, are more suitable for materials that meltor sinter; the liners prevent contamination of theDTA thermocouples. The macrocups alsoenable you to use large samples for increasedsensitivity.

Two liner materials are available for themacrocups: alumina (ceramic) and platinum.Alumina is more porous than platinum but isotherwise sufficient for most experiments and ismore economical. Advantages of the platinumliners include a slightly larger capacity due tothe thinner walls and a reduced thermal gradientbetween the liner and the sample. The mostimportant criterion in choosing a liner materialis its reactivity with the sample; make sure theliner you choose will not amalgamate or fusewith your sample.

If you do not use a sample cup liner, the samplecould melt and fuse with the thermocouple, whichwould then need to be replaced.

ttttt CAUTION:


Loading the Sample

I f the 1600°C DTA has just been used, theinside of the furnace may be extremely hot .Before loading another sample, e ither waitfor the temperature to cool to ambient, orwear appropriate protect ive gloves.

1. Remove the Pyrex* cap from the furnacetube. If the furnace tube is hot, the Pyrexcap may not come loose, owing to differen-tial thermal expansion of the tube and cap.Wait for the tube to cool. Do not force thecap off.

2. Unscrew the two furnace assembly thumb-screws, and carefully lift the furnace off thefurnace base. Lift the furnace straight up toavoid damaging the furnace tube (see FigureDTA.14).

Figure DTA.14Removing the1600oC DTA Furnace

* Pyrex is a registered trademark of Corning Glass Works.

!!!!!WARNING


Appendix



4. Remove the thumbscrews holding the belljar and furnace tube assembly. Then slowlylift the whole assembly off the cell.

Be careful not to bump the furnace tube againstthe thermocouples while removing it. Even aslight bump could crack the ceramic sleeve of athermocouple. If a thermocouple sleeve iscracked, it must be replaced.

5. Weigh and fill your sample cup. Followthese directions when using macrocup:

a. Using tweezers, place a macrocup oneach thermocouple. Make sure themacrocups touch bottom on the posts.

b. Weigh the sample, and then place it in aplatinum or alumina liner. Place theliner in the macrocup on the left.

Before you weigh your sample, make a smallStyrofoam* holder for the liner. Then weigh theholder and the liner, weigh the sample inside theholder/liner combination, and subtract. This willreduce spillage during weighing.

c. Fill another liner with reference material(e.g., Al

2O

3). To minimize baseline

slope caused by weight differencesbetween the sample and reference, fillthe reference liner to the same height asthe sample.

d. Place the reference liner in the macro-cup on the right. Ensure that the twomacrocups are vertical (not slanted) andthat they do not touch each other.

* Styrofoam is a registered trademark of the DowChemical company.

ttttt CAUTION:

NOTE:


5. Carefully replace the bell jar and furnacetube assembly over the thermocoupleassembly. Replace the thumbscrews at thebase of the bell jar. Make sure there is acomplete seal between the bell jar and thegasket around its circumference.

6. Carefully replace the furnace. Push down onthe back of the furnace to seat it on thefurnace base. Evenly tighten the two furnaceassembly thumbscrews.

7. Look down the furnace tube and ensure thatit is aligned within the furnace and is nottouching the furnace.

8. Place the Pyrex cap on the furnace tube.

Intense heat wi l l r ise from the furnace tubeif the Pyrex cap is removed whi le the cel l ishot. Do not al low your hand, face, or anycombustible material to touch or passdirect ly over the furnace tube.

If you are using purge gas, a Pyrex cap with sidearm can be used. The side arm allows purging ofthe cell either from the base, through the cell, andout the furnace tube top, or from the top, down,and out the base. The baseline slope is not af-fected by the flow direction.

Differential thermal expansion (seizing) maymake the Pyrex cap difficult to remove from thealumina furnace tube immediately after a run.To prevent seizing, apply an anti-seize com-pound to the outer surface of the furnace tubeends before placing the cap on the tube. Re-move the compound for vacuum operation. Wesuggest the following compound: “Never-Seez,”available from Bostik Chemical Group, 2910South 18th Avenue, Broadview, IL

!!!!!WARNING

NOTE:


Appendix


Purging the CE 1600°C DTA Cell

A purge gas can be connected to either thePURGE port on the DSC 2920 CE or the DTAfurnace cap with side arm. If you connect thepurge to the furnace cap, make sure the 2920CE's PURGE port is open to allow the purge gasto exit.

Using the furnace cap with side arm, you canpurge the cell from the bottom up (from theinstrument PURGE port to the furnace cap) orfrom the top down (from the furnace cap to thePURGE port); the direction depends on the typeof sample environment desired and the type ofpurge gas used. For example, if you want a purenitrogen environment (with no air intermixed),purge from the bottom up. In general, heavypurge gases should flow from the bottom up, andlight gases should flow from the top down.

Do not use hydrogen or any other explosivegas with the DSC 2920 CE.

For a list of recommended gases, see TableDTA.1 (page DTA-10). The presence of plati-num should be considered in the choice of purgegas, because it may be a catalyst for a reaction.

The closed furnace cap must not be usedwhen purging, because pressure maydevelop, causing the cap to be ejected.

!!!!!WARNING

!!!!!WARNING


Before you begin your experiment, set the purgegas flow rate, and ensure that your supply ofpurge gas is sufficient for the needs of theexperiment.

Cap the VACUUM port whenever you purge intothe PURGE port when using the furnace cap withside arm. This can be done with a clamped piece offlexible tubing fitted to the port. If you use a closedfurnace cap, however, closing off the VACUUMport will cause pressure buildup.

NOTE:


Appendix


Stopping an Experiment

The procedure for stopping a DTA experiment isthe same as that for a DSC experiment, with thefollowing precautions regarding the Pyrex cap.

Intense heat wi l l r ise from the furnace tubeif the Pyrex cap is removed whi le the cel l ishot. Do not al low your hand, face, or anycombustible material to touch or passdirect ly over the furnace tube.

Differential thermal expansion (seizing) maymake the Pyrex cap difficult to remove fromthe alumina furnace tube immediately after arun. Wait several minutes for the cap andfurnace tube to cool before removing it. An anti-seizing compound recommended for the 1600°CDTA is listed on page DTA-35.

!!!!!WARNING


ReplacementParts

Table DTA.5List of CE 1600°CDTA Cell Parts


251542.000 Pyrex cap

900711.901 Platinum liners

900712.901 Alumina liners

900713.901 Platinum sample holders

900936.001 Furnace tube

917010.901 One matched pair ofplatinum/platinumrhodium 1600°C DTAthermocouples

Replacement Parts

Appendix


Ordering Information

For information orto place an order,contact:

United States:

TA Instruments, Inc.109 Lukens DriveNew Castle, DE 19720Telephone: (302) 427-4000 or (302) 427-4040Fax: (302) 427-4001

Overseas:

TA Instruments Ltd.Europe HouseBilton CentreCleeve RoadLeatherhead, Surrey KT22 7UQEnglandTelephone: 44-1-372-360363Fax: 44-1-372-360135

TA Instruments GmbHSiemenstrasse 164755 AlzenauGermanyTelephone: 49-6023-30044Fax: 49-6023-30823

TA Instruments BeneluxOttergemsesteenweg 461B-9000 GentBelgiumTelephone: 32-9-220-79-89Fax: 32-9-220-83-21


TA Instruments JapanNo. 5 Koike Bldg.1-3-12 KitashinagawaShinagawa-Ku, Tokyo 140JapanTelephone: 813/3450-0981Fax: 813/3450-1322

TA Instruments France18 Rue Jean-BartParc D'Activities De La Grande Ile78960 Voisins-Le-BretonneuxFranceTelephone: 33-01-30489460Fax: 33-01-30489451

TA Instruments SpainAvienda Europe 21Planta Baja28100 AlcobendaMadrid, SpainTelephone: 34(9) 16618448Fax: 34(9) 16610655

For technicalassistance orservice in theUnited States:

HELPLINEFor technical assistance with current orpotential thermal analysis applications,please call the Thermal Analysis Hotlineat (302) 427-4070.

SERVICEFor instrument service and repairs,please call (302) 427-4050.

Ordering Information

Appendix


TA Instruments CE DTA Cell I�1

Index

Index

A

adjustmentsusing x and y screws 30using z screws 30

aligningcell furnace 26

anti-seize compound 35

atmospherecell 10

C

calibration rod 28

CE compliance information 7

celladjustment screws

location 27connector cover 22description 9, 11establishing contact 24furnace

alignment 26 to 30installation 14 to 15, 23 to 25

furnace 23furnace tube 18

installing 23liners 32loading samples 33parts list 39

cell (cont'd)purging 36sliding onto DSC 24temperature precision 10thermocouple 18thermocouple distance 20x- and y- adjustment screws 28z-adjustment screw 29

connector coverreplacing 22

D

description 9

DTAprinciples of operation 13 to 15

E

experimentsDTA 31procedure 31stopping 38

F

furnaceadjustments 26aligning 26calibration rod 29description 11installing over furnace tube 23removing 33

Appendix

I�2 TA Instruments CE DTA Cell

furnace tube 23, 34installing 16 to 25

furnace tube alignment 35

G

gas 36purge 36recommended 36

H

Helplines to TA Instruments 6

I

installationcell 14 to 15, 23furnace tube 16 to 25thermocouple assembly 18

L

label 8

linersplatinum 32

locking collar 26

M

macrocups 12, 32, 34

P

parts list 39

pressurecell 10

PURGE port 36, 37

purgingcell 36, 36 to 41

Pyrex cap 33, 38side arm 35

R

reference material 34

reordering information 40

S

safety 7CE specifications 7standards 7

sampleloading 33weighing 34

sample cupliner 32positioning 34selecting for DTA 32

samples 32loading 12

TA Instruments CE DTA Cell I�3

Index

seizing 35, 38

shielding doors 22specifications 10

stoppingexperiments 38

T

TA Instrumentsaddresses 40HELPLINE 41

technical description 11

temperature precisioncell 10

thermal expansion 35

thermocoupledistance 20

adjusting 20plugging in 21

thermocouple assembly 11installing 18

V

VACUUM port 37

W

weighingsample 34

X

x and y screws 27

Z

z-adjustment screws 29

Appendix

I�4 TA Instruments CE DTA Cell

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