Rheology Brochure

Rheometers

TA INSTRUMENTS

Rheology brochure 2009.qxp:Rheology 1/19/09 11:28 AM Page 1

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ARES-G2ARES-G2 Rheometer 1Technical Specifications 2ARES-G2 Technology - Transducer 3ARES-G2 Technology - Motor 5ARES-G2 Technology 7Environmental Systems 11 Accessories 14Applications 35Geometries 41

AR RHEOMETERS

AR-G2 Rheometer 15Technical Specifications 16AR 2000ex Rheometer 17Technical Specifications 18AR 1500ex Rheometer 19Technical Specifications 20AR Technology 21Smart SwapTM Accessories 27Applications 35Geometries 41


PURE • ROBUST •INDUSTRY STANDARD

ARES-G2



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The new ARES-G2 is the most distinctive rotational rheometer for advanced research and material development. It represents theculmination of five years of ground-up intensive R&D effort, and stands as a testament to TA’s commitment to innovation and continualimprovement to the fundamental rheological measurement. The ARES-G2 remains the only commercially available rheometer to offer unique separate motor and transducer technology for the purest rheological measurements. No other rheometeris capable of measuring stress independently of the applied shear deformation. Unrivaled accuracy, flexibility, and ease-of-use arerealized through improved specifications, new environmental systems, advanced options, expanded test modes, and new intuitiveTRIOS Software with seamless test sequencing capability.

ARES-G2

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Test station

Transducer Force/Torque Rebalance Minimum Torque in Oscillation 0.05 μN.mMinimum Torque in Steady Shear 0.1μN.mMaximum Torque 200 mN.mTorque Resolution 1nN.mNormal/Axial Force Range 0.001 to 20 NMotor Brushless DCMotor Bearings Jeweled AirStrain Resolution 0.04 μradMin Angular Displacement in Oscillation 1 μradMax Angular Displacement in Steady Shear UnlimitedAngular Velocity Range 1 x 10-6 rad/s to 300 rad/sAngular Frequency Range 1 x 10-7 to 628 rad/sStep Change in Velocity 5 msStep Change in Strain 10 ms

Temperature Systems

Smart Swap StandardForce Convection Oven, FCO -150 to 600˚CFCO Camera Viewer OptionalPeltier Plate -40 to 180˚CSealed Bath -10 to 150˚C

TECHNICAL SPECIFICATIONS


The ARES-G2 features a new force/torque rebalancetransducer, referred to as an FRT. In an FRT, linear and rotational motors are driven to maintain zero deflection asmeasured by a highly sensitive position sensor. The current output of the motor is a measurement of the reactive force or torque generated in the sample. The newFRT features a stiffer and more robust air bearing, lower operating temperatures for improved stability, a higherresolution capacitive angle sensor, and new non-contactupper temperature sensor. The wider dynamic torquerange of 5,000,000:1 enables a single transducer tomeasure extremely low viscosity dispersions as well ashigh modulus composites and thermosetting materials.The independent torque measurement eliminates the needto correct for motor friction and inertia, which is necessaryin combined motor and transducer designs. This translatesto a pure torque measurement that does not rely on sample and test parameter dependent calibrations permitting accurate and precise viscosity-independent oscillatory measurements to 628 rad/s (100 Hz).

ARES-G2 TECHNOLOGYTorque and Normal Force Transducer

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FORCE REBALANCE MOTOR ANDMAGNETIC SUSPENSION

NON-CONTACT TEMPERATURESENSOR ELECTRONICS

TORQUE REBALANCE MOTOR

TORQUE/NORMAL FORCEREBALANCE ELECTRONICS

RADIAL AIR BEARING

UPPER GEOMETRY MOUNT


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The ARES-G2 drive motor is designed to deliver the mostaccurate frictionless rotational motion over wide rangesof angular displacements and speeds. Key componentsof the design include air bearings, a brushless DCmotor, patented non-contact temperature sensing, andan optical encoder. The thrust and radial bearings provide friction-free rigid support with excellentconcentricity and no axial run-out for superior shear andnormal force measurements. The low-friction brushlessmotor and non-contact temperature sensor enhancemeasurements in a number of ways. Because the systemcan rotate freely with no stick, pure small angle sinusoidal displacements are obtained. In addition,faster response times are realized, and by combiningwith digital signal processing (DSP) electronics, creepand recovery measurements are easily performed.

ARES-G2 TECHNOLOGYAdvanced Brushless DC Drive Motor


A high-resolution optical encoder measures and controls angular deflection over exceptionally wide rangesgreatly improving traditional oscillation and transient strain-controlled testing performance. The opticalencoder allows testing to be started in any position for all test modes, and with no preferred home position in oscillation, tests are seamlessly combined with smooth transition and timely response.

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THRUST AIR BEARING

RADIAL AIR BEARING

BRUSHLESS DC MOTOR

OPTICAL ENCODER

NON-CONTACTTEMPERATURE SENSOR

ELECTRONICS

LOWER GEOMETRY MOUNT


ARES-G2 TECHNOLOGY

SEPARATE ELECTRONICS AND ENVIRONMENTAL BOXES

The ARES-G2 features a test station and a separate electronics box which houses the main power supply and any electronics cooling fans. This approach isolates the test station from heat and vibration and ensures the best sensitivity and data quality from the teststation. There are also two additional independent power and temperature system control boxes: one is for the popular Forced ConvectionOven FCO, and one is a universal control box for all other environmental options. The environmental control boxes stand only five incheshigh and stack neatly and securely on top of the test station control box. The separation of the environmental power and control fromthe main electronics truly makes the ARES-G2 a modular plug and play system.

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FRAME, VERTICAL MOVEMENT, AND ALIGNMENT

The ARES-G2 frame and vertical movement assembly is built to deliver maximum overall stiffness and the most accurate geometry positioning and alignment available. The frame pieces are made of cast ductile iron, providing high strength, optimum damping for highfrequency testing, and dimensional stability over a wide temperature range. The transducer mount is held rigidly against the frame bytwo hardened steel cross roller slides. The slides provide smooth vertical movement of the head while maintaining concentricity and parallelism, such as when setting a gap in parallel plates. The transducer head is positioned vertically via a precision ground lead screwattached to a micro-stepping motor by a rigid preloaded duplex bearing, eliminating backlash. A linear optical encoder is mounted directlybetween the stationary frame and moving bracket for precision head positioning independent of the lead screw movement to an accuracy of 0.1 micron.

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TRANSDUCER MOUNT

DUCTILE IRON FRAME

OPTICAL ENCODER

LEAD SCREW

LINEAR SLIDE

MICRO-STEPPING MOTOR

DUPLEX BEARING


ARES-G2 TECHNOLOGY

ACCESSORY RAILS

ARES-G2 offers accessory rails for mounting some standard options,such as the force convection oven and draft shield, or they can beused for easily adapting custom rheometer accessories. The rails aremountable onto both the left and right side of the instrument frame,and have 180 degrees of rotation.

ACTIVE TEMPERATURE CONTROL

The ARES-G2 incorporates our newly-patented, non-contact temperature sensor technology for active measurement and control of both the upper and lower plate temperature. PlatinumResistance Thermometers (PRT) can be installed into the shaft ofboth the motor and transducer. When installed, the PRT connector engages a micro printed circuit board (PCB) on the rotating shaft. The tip of the PRT is placed in intimate contact withthe center of an upper cone or plate and/or lower plate geometry.The PRT senses the temperature and transmits the signal to a secondary coil housed in the stationary part of the transducerand/or motor assemblies. The ability to measure and control temperature at the surface of both plates is unique patented technology. This frictionless technology enables temperature sensingon the transducer side with no impact on sensitivity, and on themotor assembly, allows for greater accuracy in small amplitude oscillation testing. Temperature control and measurements aremade at the testing surface, which is in intimate contact with thesample, without impacting the measurement.

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FULLY INTEGRATED FAST DATA ACQUISITION

The ARES-G2 provides fully integrated fast data acquisition for transient and oscillatory testing using 5 fast data channels. This allows simultaneous collection of angular displacement, torque and normal force in all test modes. The high data sampling rate of 8kHz in oscillation mode provides better resolution of both the magnitude and phase of the measured signals and allows better harmonic resolutionwith accurate evaluation up to the 10th harmonic.

TRIOS SOFTWARE AND EXTREME TESTING FLEXIBILITY

An important new feature of the ARES-G2 is a new level of testing freedom and flexibility. All key components of the rheometer (motor,transducer, data acquisition, environmental controls, axial slide etc.) are independent units with their own intelligence, all of which areorchestrated by test instructions programmed with new TRIOS software interface. While this versatile and intuitive software interfaceprovides fast and simple programming of well known general procedures for traditional testing, (eg. strain/frequency sweeps, step well-known strain, etc.), rigid limitations of pre-programmed test modes at the instrument level no longer exist. Instead, test or test sequencespecific instrument instructions are easily programmed in countless combinations and downloaded prior to the start of the experiment.

TOUCH SCREEN AND KEY PAD

The ARES-G2 features a color touch screen user interface mounted on the front of the test station. This graphical interface adds a new dimension in ease-of-use. Interactive activities such as gap zeroing, sample loading and setting temperature canbe conveniently performed at the test station. It alsodisplays instrument status and test information (torque,normal force, sample temperature) and provides easyaccess to system information such as settings and diagnostic reporting.

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FORCED CONVECTION OVEN (FCO)

The Forced Convection Oven (FCO) is an air/N2 gas convection oven designed for optimum temperature stability, extremely rapidheating and cooling, and ease of use over the temperature range of –150 to 600 °C. The maximum controlled heating rate is 60 °C/min and an optional liquid nitrogen-cooling device is available for operation to –150 °C. The FCO, used primarily forpolymer melts and solids, provides superior temperature stability through the use of twin element heaters, which produce counter rotating airflow into a newly designed barrel shaped chamber, and three internal platinum resistance thermometers (PRT) at the top,middle and bottom of the chamber. The FCO features our new flexible accessory rail mounting system allowing oven installation onboth the left and right side of the ARES-G2 test station, and comes standard with a long life internal LED lamp and sight glass foreasy sample viewing during operation. The FCO can be optionally equipped with a new camera viewer with remote illuminationand focusing. Used in conjunction with streaming video and image capture software, real-time images can be displayed in the software and an image is stored with each data point for subsequent viewing. The FCO camera viewer is an ideal tool for data validation. The FCO can be used with parallel plates, cone and plate, disposable plates, our new torsion rectangular fixture andthe extensional viscosity fixture (EVF)

The ARES-G2 offers the convenience of smart swap temperature control options, which are automaticallydetected and configured when attached.

ARES-G2 ENVIRONMENTAL SYSTEMS


PELTIER PLATE

The Peltier Plate is a smart swap temperature control option providing a temperature range of –40 to 180 °C, with a maximum heating rate of 30 °C/min, and temperature accuracy of +/- 0.1 °C. A platinum resistance thermometer (PRT) sensor is positioned in the middle of the lowersample plate and ensures accurate measurement and control of sampletemperature. It is the most common system for standard parallel plate andcone and plate testing of structured fluids. The open design facilitates easysample loading and cleaning of geometries. A new optional Solvent Trapand Purge Cover accessory is available for use with the Peltier plate.When used as a solvent trap, (to keep samples from volatilizing (drying)during experiments), the sample is fully isolated from the surrounding atmosphere by a fluid seal at the top (transducer side) and permanentseal at the bottom (motor side). A circular well containing solvent can alsobe attached and placed in contact with the Peltier plate surface. This allowsthe solvent to evaporate and create a saturated atmosphere inside the enclosure. Gases can be introduced through the purge ports. For examplea dry air or nitrogen purge keeps moisture from condensing around thesample while testing below room temperature.

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RECIRCULATING FLUID BATH

The Recirculating Fluid Bath option can be used withparallel plate, cone and plate, and concentric cylindergeometries. Concentric cylinders are especially usefulfor very low viscosity fluids, dispersions of limited stability and for applications where fluid/solvent evaporation may be a concern. The option requires acomputer-controlled fluid circulator for automated temperature control operation. The temperature rangeis –10 to 150 °C with appropriate circulator and circulating fluid.

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EXTENSIONAL VISCOSITY FIXTURE, (EVF)

The EVF is a patent-pending extensional viscosity fixture for measurementsof the elongation viscosity of high viscosity materials, such as polymermelts, dough, adhesives, etc. The EVF can be used on ARES systems configured with the convection oven. The fixture consists of a fixed androtating drum, which winds up the sample at constant strain rate, whilemeasuring the force generated in the sample. Since the torque measurement is decoupled from the motor, no bearing friction correctionis required. The maximum Hencky strain with one rotation is four, and themaximum operating temperature is 350 °C.

ARES-G2 ACCESSORIES

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SENSITIVE • VERSATILE •RELIABLE

AR



TA Instruments is proud to announce another breakthrough in rheometer technology. The new AR-G2 is the first commercial rheometerwith patented(1) magnetic thrust bearing technology for ultra-low, nano-torque control. The AR-G2 is packed with new features includingnew patented(2) advanced drag cup motor technology, Smart Swap™ (3) Geometries, streaming video and image capture software,ETC camera viewer and ethernet communications. With improvements in nearly every rheometer specification, the performance ofthe AR-G2 stands alone. It is the most advanced controlled stress, direct strain and controlled rate rheometer available.

AR-G2

(1) Patent # 7,017,393 (2) Patent # 6,798,099 (3) Patent # 6,952,95015


Minimum Torque Oscillation CR 0.003 μN.mMinimum Torque Oscillation CS 0.003 μN.mMinimum Torque Steady CR 0.01 μN.mMinimum Torque Steady CS 0.01 μN.mMaximum Torque 200 mN.mTorque Resolution 0.1 nN.m[1]

Motor Inertia 18 μN.m.sAngular Velocity Range CS 0 to 300 rad/sAngular Velocity Range CR 1.4E-9 to 300 rad/sFrequency Range 7.5E-7 to 628 rad/sDisplacement Resolution 25 nradStep Change in Velocity 7 msStep Change in Strain 30 msDirect Strain Control Standard[2]

Thrust Bearing MagneticNormal/Axial Force Range 0.005 to 50 NSmart Swap™ StandardSmart Swap Geometry StandardPeltier Plate -40 to 200 °C[3]

Environmental Test Chamber (ETC) -160 to 600 °CETC Camera Viewer OptionalConcentric Cylinder -20 to 150 °C[3]

Peltier ControlUpper Heated Plate -30 to 150 °C[3]

Electrically Heated Plate (EHP) -70 to 400 °CCamera Option with StreamingVideo and Image Capture Optional


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CR - Controlled Rate ModeCS - Controlled Stress Mode[1] Internal Resolution for D to A converter at torque of 0.1 µN.m[2] Direct Strain Control provides single cycle oscillation and continuous oscillations during experiments.[3] Lower temperature limits require use of a suitable fluid in an external circulator.


The AR 2000ex brings an all new electronics package to the time-tested hardware of the world’s best selling rheometer, further extendingthe long list of unique features. The AR 2000ex rheometer design includes a unique, ultra-low inertia drag cup motor and porouscarbon air bearings for outstanding controlled stress, direct strain and controlled rate performance. The AR 2000ex features the originalSmart Swap™ quick interchanging and self-configuring environmental systems. Enhanced features of the AR 2000ex include the newETC with fast heating rates, ETC and Peltier Camera Viewers (with image capture software), a new Electrically Heated Plate TemperatureSystem, and ethernet communications. The AR 2000ex is extremely versatile and appropriate for a wide variety of applications includingfluids of any viscosity, polymer melts, solids and reactive materials.

AR 2000ex

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Minimum Torque Oscillation CR 0.03 μN.m

Minimum Torque Oscillation CS 0.1 μN.m

Minimum Torque Steady CR 0.05 μN.m

Minimum Torque Steady CS 0.1 μN.m

Maximum Torque 200 mN.m

Torque Resolution 1 nN.m[1]

Motor Inertia 15 μN.m.s

Angular Velocity Range CS 0 to 300 rad/s

Angular Velocity Range CR 1E-8 to 300 rad/s

Frequency Range 7.5E-7 to 628 rad/s

Displacement Resolution 40 nrad

Step Change in Velocity 25 ms

Step Change in Strain 60 ms

Direct Strain Control Standard[2]

Thrust Bearing Porous Carbon Air

Normal/Axial Force Range 0.005 to 50 N

Smart Swap™ Standard

Peltier Plate -40 to 200 °C[3]

Environmental Test Chamber (ETC) -160 to 600 °C

Concentric Cylinder -20 to 150 °C[3]

Peltier Control

Upper Heated Plate -30 to 150 °C[3]

Electrically Heated Plate (EHP) -70 to 400 °C


CR - Controlled Rate ModeCS - Controlled Stress Mode[1] Internal Resolution for D to A converter at torque of 0.1 µN.m[2] Direct Strain Control provides single cycle oscillation and continuous oscillations during experiments.[3] Lower temperature limits require use of a suitable fluid in an external circulator.


AR 1500ex

The new AR 1500ex is a highly sensitive and rugged general-purpose rheometer for fluids and soft solids. It includes many of thesame design features incorporated in our AR-G2 and AR 2000ex, such as high-resolution optical encoder, durable porous carbonbearings with low residual torque, and a low-inertia drag cup motor. The AR 1500ex has broad specification ranges and a widevariety of popular Smart Swap™ temperature systems including Peltier Plates, Peltier Concentric Cylinder, Electrically Heated Plates,and both a Dry Asphalt System and Asphalt Submersion Cell. The AR 1500ex offers unprecedented value in a robust cost-effectivepackage for both research and quality control.

AR 1500ex

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Minimum Torque 0.1 μN.m

Maximum Torque 150 mN.m

Torque Resolution 1 nN.m[1]

Motor Inertia 15 μN.m.s

Angular Velocity Range CS 0 to 300 rad/s

Angular Velocity Range CR 1.00E-7 to 300 rad/s

Frequency Range 7.50E-7 to 628 rad/s

Displacement Resolution 40 nrad

Step Change in Velocity 25ms

Step Change in Strain 6 0ms

Thrust Air Bearing Porous Carbon

Smart SwapTM Standard

Peltier Plate -40 to 200 °C[2]

Peltier Plate Camera Optional

Peltier Concentric Cylinder -20 to 150 °C[2]

Upper Heated Plate -30 to 150 °C[2]

Electrical Heated Plates -70 to 400 °C

[1] Internal Resolution for D to A converter at torque of 1 µN.m[2] Lower temperature limits require use of a suitable fluid in an external circulator.



AR TECHNOLOGYThe AR series represents a family of rheometers uniquely designed to deliveroptimum system performance.

1 DRAG CUP MOTOR

The motor applies torque, and controls speed and oscillation frequency. Drag cup motors, unlike some motor designs, can apply extremely smooth acceleration and are ideal for creep and recovery measurements. Inertia is kept to an absolute minimum, reducing the influence of the system on test results in oscillation and transient measurements. The result is more accurate measurements of weak material structures and faster response to step changes in torque and strain.

2 THRUST BEARING

Thrust bearings provide stiff, “frictionless” axial support of the drive shaft and measuring geometry. The low-end torque performance of the instrument depends on residual bearing friction, which results in residual torques. The AR-G2 incorporates the new magnetic thrust bearing while the AR 2000ex and AR 1500ex use porous carbon bearings.

3 RADIAL BEARINGS

Radial air bearings provide stiffness and support in the radial direction. All AR Rheometers are uniquely designed with twoporous carbon radial bearings. The dual radial bearing design is ideal for the testing of high-stiffness samples, such assolids in torsion as well as soft solids and low-viscosity fluids.

4 OPTICAL ENCODER

Low-inertia optical encoders are used in all AR rheometers for high-resolution measurement of angular displacement (strain) andspeed (shear rate) over wide ranges. The ability to measure verysmall displacements allows for the characterization of very delicate material structures. The ability to measure and control a wide rangeof speed adds to the instrument’s versatility.

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5 NORMAL FORCE TRANSDUCER

A unique AR rheometer feature is the design and placementof the normal force sensor. The highly-sensitive, ultra-stiff, normal force sensor is isolated from the motor and bearing assembly, and located below the lower geometry. The benefitof isolating the normal force transducer is twofold. First, boththe normal force sensor and the motor/bearing assembly aredesigned for maximum stiffness. When shearing a viscoelasticmaterial, the normal force generated by the sample pushesagainst the measuring surfaces. Minimizing movement is keyto accurate normal force measurements. Second, the normalforce sensor is environmentally isolated for thermal stability.

6 RIGID ONE-PIECE ALUMINUM CASTING

& LINEAR BALL SLIDE

All TA rheometers are designed to minimize system deflection in order to maximize the deformation applied to the sample. AR rheometers are built on a rigid, single-piece aluminum casting and the rheometer head assembly is attached to thecasting via a rigid linear ball slide. A motor and an optical encoder are located in the base of the frame to drive the ballslide vertically and measure its movement. This ensures precision positioning of the geometry with an accuracy of 1micron. TA Instruments’ rheometers are built to last and delivera lifetime of reliable performance.

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AR-G2 TECHNOLOGYBreakthrough technologies make our new AR-G2 the world’s mostadvanced controlled stress, direct strain and controlled raterheometer. With a revolutionary, patented, magnetic-levitationthrust bearing and new patented drag cup motor technology, unprecedented nano-torque control is now possible adding a newdimension to rheological characterization. New patented SmartSwap™ Geometries and Real-Time Streaming Video and ImageCapture features take ease-of-use to a new level. The AR-G2 represents a whole new approach to rheometer technology.

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MAGNETIC THRUST BEARING

Why a magnetic bearing? Larger gaps in the absence of a continuous flow of pressurized air translates to unprecedented low levels of friction in the bearing. Moreimportantly, the ability to control and measure torques inthe nN.m range. No other rheometer can boast such low-end torque sensitivity. The larger gap in the thrustbearing is robust and not susceptible to contamination.The additional benefits of the magnetic bearing over traditional air bearing designs are the following:

• Ultra low torques applied to the sample• Smaller sample volumes can be used• Ability to probe delicate material structures• Study of low viscosity materials over a

broad range of conditions

PATENTED DRAG CUP MOTOR

Our new patented advanced drag cup motor is designedto further reduce system friction by increasing the motor gapby 100%. Dramatic improvements in low end torque performance are realized without compromising high-endperformance. The motor delivers enhanced transient response and an extended angular velocity control range.The motor incorporates a patented drag cup temperaturesensor. For the first time in any rheometer design, the temperature of the drag cup is measured, ensuring the mostaccurate torque output.


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ACTIVE TEMPERATURE CONTROL (ATC)

The AR-G2 Electrically Heated Plate (EHP), Upper Heated Plate (UHP),and Dry Asphalt System all incorporate our new patented(1) non-con-tact temperature sensor for active measurement and control of theupper plate temperature, using a special draw rod. The draw rodhouses a micro PCB and Platinum Resistance Thermometer.

AR-G2 TECHNOLOGY

The PRT senses temperature at the upper cone or plate geometry, and the signal is transmitted from a secondary coil on the drawrod to a primary coil in the head assembly. Together with a PRT in the lower plate, real-time control of both plates is possible. TheAR-G2 is the first rheometer to actively measure and control the upper plate temperature. (1) Patent # 6,931,915

MICRO PCB

PRIMARY COILSECONDARY COIL

PRT

HOUSING


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SMART SWAP™ GEOMETRIES

The AR-G2 features our new patented Smart Swap Geometries with automatic detection. Smart Swap geometries include an integratedmagnetic cylinder that stores unique geometry information. When attached, the information is automatically read and the software isconfigured with appropriate parameters (type, dimension, material).The Smart Swap option brings the AR-G2 one step closer to being atruly “intelligent” rheometer system.


PELTIER PLATE

The most common temperature control option for the AR rheometers is the Peltier Plate. AR Series Peltier Plates have a temperature range of-40 to 200 °C with a typical heating rate of up to 20 °C /min and a temperature accuracy of +/- 0.1 °C. A PRT (platinum resistance thermometer) sensor positioned at the center of the plate ensures accurate temperature measurement and control. The Peltier Plate is also available in a “stepped” model that uses removable lower plates. This unique design allows the Peltier Plate to easily be configured with customlower plates and cups. Other Peltier accessories include: Peltier immersion cover, solvent trap, purge cover, and camera viewer.

SMART SWAPTM ACCESSORIESSMART SWAP™ TEMPERATURE SYSTEMS

Only TA Instruments offers the convenience and versatility of SmartSwap temperature control options. Smart Swap temperature control options are attached to the instrument on its unique magnetic base. Intelligent Smart Swap options can be interchanged in as fast as 10 seconds. Once attached, the instrument automatically detects and configures the system.

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CONCENTRIC CYLINDER

Concentric Cylinders are commonly used for very low viscosity fluids,dispersions of limited stability, and applications where fluid/solventevaporation may be a problem. The Smart Swap Concentric Cylindersystem features Peltier temperature control and provides a temperaturerange of -20 to 150 °C with heating rates up to 15 °C/min.

UPPER HEATED PLATE (UHP)

The UHP is designed for use with the Smart Swap™ Peltier Plate andprovides both upper plate temperature control and an enclosed purgegas environment. Designed for optimum heat transfer and minimumthermal equilibration time, the UHP sets a new standard in non-contactheating. Automated zero heat flow calibration yields temperature gradients of less than +/- 0.1 °C. The UHP is modeled to providematched upper and lower plate temperature during heating ramps ofup to 15 °C/min to a maximum temperature of 150 °C. The AR-G2UHP features our new patented Active Temperature Control, ATC. TheATC makes the AR-G2 UHP the only Peltier/upper heated plate systemcombination available that incorporates direct temperature control ofboth the upper and lower plates. Flexible cooling options include an external circulator or innovative vortex cooling.

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SMART SWAPTM ACCESSORIESENVIRONMENTAL TEST CHAMBER (ETC)

The ETC uses a controlled convection/radiant-heating concept and is available for AR-G2 and AR 2000ex Rheometers. It is typically used forpolymer applications and can be used with parallel plate, cone and plate,disposable plate, and rectangular torsion clamps for solids. The ETC hasa temperature range of –160 to 600 °C with heating rates up to 60 °C/min. It can be connected directly to a bulk liquid nitrogen sourcefor subambient temperature control. The ETC features our new cameraviewer with remote illumination and focusing. Used in conjunction withthe new streaming video and image capture software, real-time imagescan be displayed in the software and an image is stored with each datapoint for subsequent viewing. The ETC camera viewer is an ideal tool for data validation.

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ELECTRICALLY HEATED PLATES (EHP)

The EHP is a Smart SwapTM temperature option that provides activeheating and cooling of parallel plate and cone and plate geometries. The EHP is perfect for rheological characterization ofpolymer melts up to a maximum temperature of 400 °C. Otherfeatures include an environmental cover and heated purge gasand an optional Gas Cooling Accessory for temperature controlto -70˚C. An optional clear purge cover is available for sampleviewing and integration with camera viewer. Additionally, for theAR-G2, the EHP offers patented Smart Swap Geometries andnewly patented Active Temperature Control, ATC. ATC makes theAR-G2 EHP the only electrically heated plate system capable of direct temperature control of both the upper and lower plates.

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SMART SWAPTM ACCESSORIES

WET ASPHALT

DRY ASPHALT

DRY ASPHALT & ASPHALT SUBMERSION

TEMPERATURE SYSTEMS

The AR Series offers a traditional Asphalt Submersion Cell and new Dry Asphalt temperature control accessories. Both temperature systems meet SHRP,ASTM, and AASHTO requirements, and include 8 mm and 25 mm parallelplates and sample molds. The Dry Asphalt System combines our superiorUpper Heated Plate with a unique lower stepped Peltier Plate. Automatedzero heat flow calibration yields temperature gradients of less that +/- 0.1°C.The AR-G2 Dry Asphalt System features our newly-patented Active Temperature Control, ATC. The ATC makes the AR-G2 Dry Asphalt systemthe only stepped Peltier/upper heated plate system combination availablethat incorporates direct temperature control of both the upper and lowerplates. Flexible cooling options includes an external circulator or innovativevortex cooling. The Asphalt Submersion Cell is a direct port of temperaturecontrol technology used on our popular CSA series of rheometers. Temperature control of an asphalt sample is by fluid submersion.

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UV CURING

Two Smart Swap accessories for rheological characterization of UVcurable materials are available for the AR-G2 and AR2000ex rheometers. One accessory uses a light guide and reflecting mirror assembly to transfer UV radiation from a high-pressure mercury lightsource. The UV Light Guide accessory is configured using a lowerSmart Swap assembly with light source mount, collimator, and 5 mmlight guide. A UV light source (Exfo Omnicure S2000), with wavelengths in the range of 320 to 500 nm, and triggering cable areoptional. A second accessory uses self-contained LED’s to deliver UVlight with a very narrow band around a peak of 365 nm. Both the LEDand Light Guide Accessories include removable 20 mm quartz plate,remote radiometer/dosimeter, UV light shield, and nitrogen purgecover for working under ambient conditions. Optional temperaturecontrol to a maximum of 150 °C is available using AR Series Electrically Heated Plates (EHP) option. Disposable plates are available for hard UV coatings that cannot be removed from the platesonce cured.

UV LIGHT GUIDE

UV LED

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STARCH PASTING CELL (SPC)

The SPC is a powerful and accurate tool for rheological characterization of the gelatinizationprocess and final properties of starch products. Ituses TA's innovative new impeller design for superior mixing and control of sedimentation during testing. A precision temperature controlled chamber, with heating/cooling rates up to 30 °C/min, controls and measures actual sample temperature and is designed to minimize water lossduring the cooking cycle.

PRESSURE CELL

The Pressure Cell is an optional accessory for use with the Peltier-controlled Smart Swap Concentric Cylinder System. The Pressure Cell isa sealed vessel that can be pressurized to 140bar (2000 PSI), over a temperature range of -10 °C to 150 °C. The cylinder in the vessel is driven using an innovative high-powered magnetic coupling and low-friction bearing design. The cell is ideal for characterizing materials that volatilize under atmospheric pressure.

SMART SWAPTM ACCESSORIES

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DYNAMIC INTERFACIAL SHEAR

RHEOLOGY USING THE AR-G2

The dynamic interfacial shear moduli G’ and G” are used tomonitor the network structure build-up, resulting from the adsorption of proteins at the interface. Proteins unfold at theinterface and, therefore, are crucial to the stability of emulsions and foams. The measurement is done with a DuNoüy Ring, positioned at the interface of two liquids, or aliquid and air in a circular glass dish. The ultra-sensitive,nano-torque range of the AR-G2 rheometer is required tomake these measurements. Figure 1 shows the dynamicstorage modulus of this material continuously increases as theprotein migrates to the surface and forms a network structure.

INTERFACIAL ACCESSORY

Traditionally, rheometers have been used to characterize thebulk properties of materials. In many materials, such as pharmaceuticals, foods, personal care products and coatings,there is a two-dimensional liquid/liquid or gas/liquid phasewith distinct rheological properties. In the past, massive biconical geometries have been used to make limited interfacialmeasurements in steady shear mode. The ultra-low friction nano-torque sensitivity of the AR-G2 has now been combinedwith a Pt/Ir Du Noüy Ring system, enabling viscoelastic characterization of interfaces in oscillation and transient modes.This makes the AR-G2 the only rheometer in the world capableof measuring bulk rheology, as well as both steady shear anddynamic interfacial properties of materials.

0.03

0.025

0.02

0.015

0.01

0.005

0

0 50 100 150

time (minutes)

G‘,

G’’ (

N/m

)

Figure 1: Absorption of a 0.05% whey protein solution in distilled water.

FIGURE 1

34


FLOW CURVE FOR DISPERSIONS

A generalized flow curve for dispersions is illustrated below. TA rheometers generate flow curves by applying a stress ramp (orshear rate) and measuring the shear rate (or stress). Flow curvescan also be produced using “steady state” flow where each viscosity data point is generated at a constant stress after equilibration. The data generated provides information on yieldstress, viscosity, shear thinning, shear thickening, thixotropy, andcorrelates to processing and product performance. Simple techniques like spindle viscometers can only measure a point ora small part of the total flow curve.

FLOW CURVE FOR POLYMERS

The figure below shows a generalized flow curve for polymersand corresponding process shear rate ranges. A polymer’s molecular weight greatly influences its zero shear viscosity, whileits molecular weight distribution and degree of branching affectits shear rate dependence. These differences are most apparentat low shear rates not possible with melt flow index or capillarydevices. TA rheometers can determine molecular weight based onthe measured zero shear viscosity. Cox-Merz and TTS can be used to extend the data to higher shear rates.

1 Sedimentation 2 Leveling, Sagging 3 Draining under gravity 4 Chewing and swallowing 5 Dip coating 6 Mixing and stirring 7 Pipe flow 8 Spraying and brushing 9 Rubbing 10 Milling pigments in fluid base 11 High Speed coating

log

η

shear rate (1/s)

10-5 10-3 10-1 101 103 105

56 8 9

4

1 2 3 117 10

Extended Range with Oscillation & Cox-Merz

Extended Range with Time-Temperature Superpositions (TTS) & Cox-MerzMeasure in Steady Shear

ηo = Zero Shear Viscosityηo = K x MWc3.4

log

ηo

shear rate (1/s)

10-310-5 10-1 101 103 105

Molecular Structure Compression Molding Extrusion Blow and Injection Molding

APPLICATIONS

35


VISCOELASTIC PROPERTIES

The viscoelastic properties of polymer melts are commonly studied in the dynamic oscillation mode. The figure below illustrates a viscoelastic fingerprint for a linear homopolymer andshows the variation of the storage modulus (GI) and loss modulus (GII) with frequency. Since polymer melts are viscoelastic, the mechanical response will be time dependent, so low frequencies correspond to long times. TTS is used to extend the range of data to higher and lower frequencies and tobuild a master curve at a reference temperature. The magnitudeand shape of the GI and GII curves depend on the molecularstructure of the polymer.

STRAIN SWEEP

Key viscoelastic parameters (G’, G”, η*, tanδ, etc.) can be measuredin oscillation as a function of stress, strain, frequency, temperatureand time. The figure below illustrates an oscillation strain sweepused to determine the onset of non-linear viscoelastic behavior. In thelinear viscoelastic region (LVR), the material responds linearly to astress or strain input and the moduli G’ and G” are independent ofstrain. The internal structure of the material remains intact under linear testing conditions. Beyond the limit of the LVR the material’s response is highly non-linear. The dynamic moduli G’ and G” drop rapidly with increasing strain and higher harmonic stress contributions appear. Under these high-strain test conditions the material experiences a catastrophic breakdown of the internal structure. Rheological analysis using higher harmonics in thenon-linear oscillation regime is referred to as “Fourier Rheology.”

Typical range Frequency sweep

log

G’ a

nd G

” (Pa

)

1011

109

107

105

103

101

10-2 100 102 104

log Frequency (rad/s)

Terminal Region

Extended range w/TTS

G'G''

Extended range w/TTS

Rubbery Plateau Region

Transition Region

Glassy Region

106 108 1010

G“G‘

Linear Region Non-Linear Region

104

103

102

101

0.0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

100

10-5

Strain

Mod

ulus

G',

G'' (

Pa)

Magnitude R

atio l3 /l1 , l5 /l1 , l7 /l1

10-1 10010-2 10110-4 10-3

36


DYNAMIC MECHANICAL PROPERTIES

OF SOLIDS IN TORSION

The ability to characterize the viscoelastic properties of solids in torsion is a feature of TA Instruments’ rheometers, as illustratedbelow for polycarbonate (PC). Transitions or relaxations of molecular segments are observed as step changes in the storage modulus, and as peaks in the loss modulus and damping.The magnitude and shape of the storage modulus (GI), loss modulus (GII) and damping (tan delta) will depend on chemical composition, crystallinity, molecular structure, degreeof cross-linking, and the type and amount of fillers.

TRANSIENT TESTS (CREEP AND STRESS

RELAXATION)

In a creep recovery test, illustrated below, a constant stress is applied to the sample and the resulting strain is measured overtime. The stress is then removed and the recovery (recoil) strainis measured. For polymer melts, the zero shear viscosity (ηo) andequilibrium recoverable compliance (Jeo) can be determined.Creep is a sensitive technique and best suited for the unmatchedstress control performance of the AR. In a stress relaxation test, astrain is applied and stress is measured as a function of time yielding stress relaxation modulus G(t). Stress relaxation can be performed on all ARES and on the AR-G2 and AR 2000ex withdirect strain control.

G'

G''

tan δ

tan

δ

log

G' a

nd G

" (Pa

)

temperature °C

1010

109

10

1

Glass transition Tg = 154.1°C

Temperature Ramp at 3°C/min Frequency = 1Hz Strain = 0.025%

0.1

.01

108

107

106

105

-200 -150 -100 -50 0 50 100 150 200 time (s)

Creep Zone: Stress > 0

Low η

High η Bad

Good

Recovery Zone: Stress = 0

stra

in

0 0

1400

APPLICATIONS

37


DYNAMIC OSCILLATION ON LOW

VISCOSITY FLUIDS USING ARES

An advantage of the ARES design is that the motor generatesthe torque to overcome the viscosity of the material, as well asthe inertia of the sample holder. As a result, the ARES can beused to conduct inertia-free measurements on the viscoelasticproperties of very low viscosity fluids. Below shows an exampleof this for a polymer solution, where the viscoelastic parametersare determined using a frequency sweep up to 100 rad/s withno inertial effects.

AR-G2 NANO-TORQUE

MEASUREMENTS IN STRESS & STRAIN

CONTROL OSCILLATION

The minimum torque on rheometer designs which use only air bearings is specified at a higher value for controlledstress (CS), as compared to controlled rate or strain (CR). The new magnetic thrust bearing and advanced drag cup technologies incorporated on the new AR-G2 allow for ultra-low, nano-torque control in both controlled stress and controlled strain modes. This unprecedented torque performance is shown below. Note, viscosity and displacementvalues at instrument torque levels of 3 nN.m.

5.0

10-3 10-2 10-1 1 10 100

η* (

Pa.s

)

osc. torque (micro N.m) di

spla

cem

ent (

rad)

15.0

10.0

7.5

2.5

0

12.5

10-7

10-6

10-5

10-4

10-2

10-1

3 nN.m

Controlled Stress Mode, CS Controlled Strain Mode, CR Newtonian Model Fit; Newtonian Viscosity = 5.537

1000

10 0

10-3

10-1

101

100

10-3

10-2

10-1

10-4

100 101 102

freq [rad/s]

η* (

) [Pa

-s]

102

10-1

10-4

102

100

101

10-2

10-3

G“ (

) [Pa

]G

‘ (

) [

Pa]

38


EXTENSIONAL VISCOSITY

MEASUREMENTS ON ARES

Extensional viscosity is fundamentally important in many polymer-processing techniques such as blow-molding, fiber spinning, and injection molding. The EVF is a polymer melt elongation fixture that transforms an ARES oven system into ashear and extensional rheometer. The EVF uses a unique patenteddual cylinder, or drum, wind-up technique. The figure belowshows the data on a LDPE sample, superposed with three timesthe shear and complex viscosity measured at a rate of 0.01 1/sand frequency w = 1/t. The EVF clearly shows excellent dataover a wide range of rates.

10-2

10-1

100

101

102

102

103

104

Elon

gatio

n Vi

scos

ity [P

a.s]

time [sec]

105

106

1 s-10.3 s-10.1 s-10.03 s-10.01 s-110 s-13 s-130 s-10.003 s-13x complex viscosity3x shear viscosity at 0.001 s-1

max=1.363x104 [Pas]

y(t)=90.696 [Pas]

6000.0

5000.0

4000.0

3000.0

2000.0

1000.0

1.6x104

1.2x104

8000.0

4000.0

500.0

400.0

300.0

200.0

100.0

0.00.0

Time [s]

Visc

osity

η (t

) (Pa

.s)

Strain γ (t)

Stress τ (Pa)

80 100 120 140 160 180

APPLICATIONS STRESS AND SHEAR RATE RAMPS

Stress and shear rate ramps are common transient experimentsthat provide fast and easy ways of characterizing yield stress andthixotropic behavior in materials. Both of these phenomena aretypical time dependent behaviors of structured fluids that are important for understanding how a material will perform in an application. The stress ramp is a standard way of measuring yieldstress of a structured fluid. While ramping the stress linearly withtime, the strain and instantaneous viscosity are recorded. It canbe seen below that the viscosity increases initially and goesthrough a maximum. The stress value at the characteristic maximum in viscosity is a measure of the yield stress. Beyond this maximum, the material’s structure breaks and the instantaneousviscosity decreases, or shear thins, with increasing stress. Rateramps are more commonly used to observe thixotropic behavior.A test procedure involving a shear rate ramp from zero to a finalrate and back to zero at constant ramping rate is referred to asthixotropic loop. The magnitude of the stress profile will be higherin the up-ramp then in the down ramp. The area between the upand down stress curves as a function of rate is called thethixotropic index.

39


CREEP AND RECOVERY OF A

VISCOELASTIC FLUID

Creep and recovery testing is well suited for measuring the effect of long relaxation times (200 sec). The strain recovery isa very sensitive measurement of elasticity. In creep a constant stressis applied and the resulting strain is monitored. Upon steady state,the stress is reduced to zero and the elastic recoil, or recovery, of the sample is measured. The elastic component of therecoil is characterized by the equilibrium compliance Je. Both theAR-G2 and ARES-G2 provide the most accurate Je data by overcoming inertial effects at the critical transition between thecreep and recovery zones. The AR-G2 offers extremely low residual torques and a creep-braking routine, while the ARES-G2offers excellent torque sensor resolution and employees a novel control algorithm. The figure below shows the creep and recoverable compliance for the NIST PIB 2490 standard referencematerial as measured on the ARES-G2. Stresses used range from100 Pa down to 0.03 Pa. The superposition of the creep as well as the recoverable compliance proves that conditions of linearity have been fulfilled at low stress. The data shown here are unprecedented on a separate motor and transducer instrument.

100 [1/s] 0.3 [1/s] 1 [1/s] 3 [1/s] 10 [1/s] 30 [1/s]

106

105

104

103

100

102

101

10-5

10-4

10-3

10-2

10-1

100

101

102

103

10-3

Time t (s)

Visc

osity

η(t)

(Pa.

s)

1st Norm

al Stress Coefficient Y

1 (t) (Pa.s2)

101 102 100 103 10-2 10-1

119.9 [Pa] 0.03596 [Pa]

J(t) for Creep Stress PIB 2490T=27.85˚CCreep Recovery

Slope: 0.9980

1.199 [Pa] 0.1199 [Pa] 3.596 [Pa] 11.99 [Pa] 35.96 [Pa] 0.3596 [Pa]

100

10-1

10-2

10-3

10-4 10-4

10-1

10-2

10-3

100

10-2

Time t (s)

Com

plia

nce

J(t)

(1/P

a)

Recoverable C

ompliance J

r (t) (1/Pa)

101 100 102 10-1

STRESS GROWTH IN A TRANSIENT

STEP RATE EXPERIMENT

Transient viscosity and first normal stress coefficient measurementson a viscoelastic material in cone plate configuration are challenging rheological measurements. The instrument must haveextremely low axial compliance in order to minimize inwardflows, which subsequently affect the normal force. The ARES G2uses a motor air bearing with high axial stiffness and a non-compliant force rebalance transducer to reduce axial movement to less than 0.1μm/N. The figure below shows resultsof a series of step rate experiments performed over a shear raterange from 0.1 to 100 1/s. The ARES-G2 can easily make thesechallenging measurements. Both transient viscosity and 1st normalstress coefficient superpose well at short times at all shear rates.At longer times, the viscosity and normal stress coefficient tracesdiverge due to the non-linear material response at higher shearrates. The characteristic overshoot in both the viscosity and the 1stnormal stress coefficient is due to changes of the material’s structure under strong shear fields.

40


GeometriesTA Instruments offers a wide range of measurement geometriesincluding parallel plate, cone and plate, concentric cylinder, disposable, and torsion solid clamps.

Parallel plate and cone and plate geometries are available for boththe ARES and AR Rheometers in an extensive variety of diametersand cone angles. Materials of construction include stainless steel,aluminum, plastic (Acrylic/PPS), or titanium. Disposable plates andcones are also available for applications such as thermoset curing.

A wide selection of concentric cylinder geometries are available forboth the ARES and AR Rheometers. Options include conical DIN,recessed, vaned, and double wall. For the ARES rheometers, thegeometries are constructed of stainless steel and titanium. For theAR rheometers, stainless steel and anodized aluminum are used.

A variety of other geometries are available for both the ARES andAR Rheometers, including clamps to measure solids in torsion usingthe high temperature ovens and immersion clamps. The ARES isavailable with many specialty fixtures including linear tack-testingfixtures, glass plates for optical measurements, and film/fiber fixtures.

41



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