machine design, Vol.6(2014) No.3, ISSN 1821-1259 pp. 91-96

*Correspondence Author’s Address: University of Oradea, Faculty of Arts, 1 Str. Universității, 410610, Oradea, Bihor, Romania, maries.radu@rdslink.ro

Research paper

STUDY ABOUT THE INFLUENCE OF PROCESSING TEMPERATURE ON SOME MECHANICAL PROPERTIES OF THE POLYETHERETHERKETONE AND THE MIXTURE OF POLYCARBONATE WITH POLYBUTYLENE TEREPHTHALATE USING METHODS OF DETERMINING THE MECHANICAL RESISTANCES Gheorghe Radu Emil MĂRIEŞ1, * 1 University of Oradea, Faculty of Arts, Oradea, Romania

Received (23.06.2014); Revised (07.08.2014); Accepted (18.08.2014) Abstract: This study presents the impact that processing temperatures has on some of the mechanical properties, when manufacturing different kind of items by injection molding, made of polyetheretherketone Victrex PEEK 90HMF40 type, and a mixture of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type. Samples of polyetheretherketone Victrex PEEK 90HMF40 type, were made at the following injection temperatures: 360°C, 370°C, 380°C, 390°C and 400°C. The mixture samples of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type were made at the following injection temperatures: 240°C, 250°C, 260°C, 270°C and 280°C. The mechanical properties were determined using the tensile test, the Izod impact strength test and the Shore indentation durometer test. It was found for the two polymers examined, that the increase of injection processing temperature leads to a negligible change in hardness. The Izod impact strengths for polyetheretherketone Victrex PEEK 90HMF40 type, decreases with the increase of the injection processing temperature up to a certain minimum value, after which further increase of injection processing temperature, leads to an increased levels of resistance to shock. In the case of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type mixture, the increase of the injection processing temperature leads to increased Izod impact resistance. Tensile strengths for the two polymers tested increase with the increasing processing temperature up to a certain maximum value, after which a further increase in processing temperature leads to a decrease of tensile resistance values. Key words: tensile tests; the Izod impact test; the Shore Durometer hardness test 1. INTRODUCTION Among the most macromolecular compounds used in manufacturing items from different industries we have: polyolefins, polyamids, thermoplastic polyurethanes, polyoxymethylenes, polycarbonates, methyl polyacrylate, cellulose acetate, vinyl polychlorure, polystyrene and polystyrene derivates, polyetheretherketones, polybutylene terephthalate, etc. The most used technologies in processing these polymers are: injection molding, extrusion, thermoforming, etc. Polyetheretherketones (PEEK) are semi crystalline thermoplastic polymers which presents a very good dimensional stability. These are rigid materials resistant to shock, tension and bending. They have an outstanding long term stress performance, marked durability, and maintain its mechanical properties over a long temperature range (from -85°C to +150°C). They have a good chemical stability when it comes to alcohols, esters, ethers, ketones, hydrocarbures, grease, oils. Polyetheretherketones are vulnerable to concentrated acids and sensitive to UV radiations. They are resistant to hydrolysis even in hot water, which makes them usable for medical equipments that need sterilization. They are good electric isolators. To increase their performances are armed with fiberglass or carbon fibers. Applications: the automotive industry (oil and vacuum pumps, seals and

supporting rings, hydraulic valves, gears, thrust washers, rolling bearing elements, electrical components), aeronautics (engine components, cabin flight interiors, air ducts), electronics (cable connectors, anti corrosion protective systems), chemical industry (pumps, vanes, probes, water gauges), medical equipments (prosthetics, microscope components), friction pieces (lock washers, pillow block bearings, cogwheels) [1-3]. The mixture of polycarbonate and polybutylene terephthalate (PC+PBT) is a formless (amorphous) material who has a high stress resistance, good dimensional stability, an excellent impact strenght resistance up to -40°C. It is stable in water and it is diesel, grease and gasoline proof. To increase some strenght and thermal performances the PC+PBT mixture can be reinforced with fiberglass or mineral binding agents. Applications: automotive industry (components in contact with fuel), home appliances (freezers, deep freezers), gardening (lawn mowers). Injection processing of polymeric materials, the ware properties are strongly influenced by the material temperature, the pressure of the molten state of the material while filling the mold cavity, the mold temperature and cooling time [4-9]. This paper discusses the variation of its mechanical properties, depending on the temperature of the injection process using the tensile stress test, Izod impact strength

Gheorghe Radu Emil Mărieş: Study about the Influence of Processing Temperature on Some Mechanical Properties of the Polyetheretherketone and the Mixture of Polycarbonate with poPlybutylene Terephthalate Using …; Machine Design, Vol.6(2014) No.3, ISSN 1821-1259; pp. 91-96

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test and Shore indentation durometer test for polyetheretherketone Victrex PEEK 90HMF40 type and the mixture of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type, polymers used for wares manufacturing in various industries. 2. EXPERIMENTAL

In making the samples the following materials were used: polyetheretherketone Victrex PEEK 90HMF40 type and polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type mixture, using an injection mold machine, ENGEL CC 100 Type ES 80/50 HL, manufactured in 1995 (Figure 1).

Fig.1. Injection mold machine ENGEL CC 100 Type ES 80/50 HL

Measuring the temperature of the molten state material has been achieved by means of thermocouples located inside the plastificaton-injection cylinder. Samples of polyetheretherketone Victrex PEEK 90HMF40 type were made at the following injection temperatures: 360°C, 370°C, 380°C, 390°C and 400°C. The mixture samples of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type were made at the following injection temperatures: 240°C, 250°C, 260°C, 270°C and 280°C. While injecting samples of polyetheretherketone Victrex PEEK 90HMF40 type and mixture samples of polycarbonate PC + PBT Makroblend KU 2-7609 type, all parameters influencing injection cycles were kept constant, modifying only the injection processing temperatures. All molded samples were subjected to the following types of mechanical measurements: determining the hardness with identation durometer (Shore hardness), Izod impact strength tests on unnotched samples and tensile stress test.

Determining hardness penetration with a D-type durometer The testing of the injected samples for those two materials was done by determining hardness penetration using the Shore type D method, with a D-type durometer, SAUTER HB make/Germany (Figure 2).

Fig.2. D-type Shore durometer, SAUTER HB make/Germany

The hardness penetration was determined for all samples by method that allows the measurement of initial penetration, and by reading the instant values indicated by the durometer (readings from the device was done within 1s from pressing). The tests were carried out in accordance with the European Standards SR EN ISO 868: 2003 [10] on samples with shapes and sizes as illustrated in Figure 3.

Fig.3. Standard sample for testing hardness For each sample have been carried out a total of 25 tests, the results expressed as the arithmetic mean of the number of the tests. Determining Izod impact strenght test properties Determination of Izod impact strenght properties was carried out on unnotched samples (Figure 4).

Gheorghe Radu Emil Mărieş: Study about the Influence of Processing Temperature on Some Mechanical Properties of the Polyetheretherketone and the Mixture of Polycarbonate with poPlybutylene Terephthalate Using …; Machine Design, Vol.6(2014) No.3, ISSN 1821-1259; pp. 91-96

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Fig.4. Standard sample for Izod impact strength test The tests were carried out in accordance with the European standards SR EN ISO 180 [11], using a pendulum impact tester, PENDOLO P400 type, HAMMEL make, England (Figure 5).

Fig.5. Izod impact pendulum tester, PENDOLO P400 type, HAMMEL make, England

According to the user manual of the device, the initial potential energy of the pendulum is 7.5 J and the initial angle of the pendulum arm is 150°. Izod impact strength

properties on unnotched samples ( iUa ) according to SR

EN ISO 180 is done using the equation:

310

bh

Ea c

iU / kJ/m² (1)

where

cE - energy absorbed to break the sample, in joule

h - the thickness of the sample in millimeters b – the width of sample in millimeters Regarding the device PENDOLO P400 type, the software automatically displays the values of the energies absorbed to break the samples. Tested samples were fixed in parallel mode. For each sample were tested a number of 10 pieces and the result was expressed as the arithmetic mean value.

Determination of tensile resistance Determination of tensile resistance for the two materials tested, was made using tensile-test machine WPM-EBV-Thuringer werk, Ranenstein Industry gerat R37, type 2092 (Figure 6).

Fig.6. Tensile-testing machine WPM-EBV-Thuringer werk, Ranenstein Industry gerat R37, Type 2092

The tests were conducted in accordance with the European standards SR EN ISO 527-1: 2000 [12] and SR EN ISO 527-2: 2000 [13] on samples with shapes and sizes as illustrated in Figure 7.

Fig.7. Standard sample for testing tensile breaking strength

The test speed for all samples was 200 mm/min. For each sample were tested a number of 10 pieces and the result was expressed as the arithmetic mean value. Tensile

Gheorghe Radu Emil Mărieş: Study about the Influence of Processing Temperature on Some Mechanical Properties of the Polyetheretherketone and the Mixture of Polycarbonate with poPlybutylene Terephthalate Using …; Machine Design, Vol.6(2014) No.3, ISSN 1821-1259; pp. 91-96

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resistance or tensile strength at break was calculated with the following equation:

AF / MPa (2)

where F - the force measured at the breaking-point moment of the sample, in N A - the initial cross-sectional area of the sample in mm²

3. RESULTS AND DISCUSSION After testing samples of polyetheretherketone Victrex PEEK 90HMF40 type and the mixture of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type, the following results of hardness penetration were obtained using a D-type durometer (Table 1). As observed, the increase of injection processing temperature on polyetheretherketone Victrex PEEK 90HMF40 type from 360°C to 380°C leads to a slight increase in the hardness of the material. The maximum hardness is recorded at a temperature of 380°C and it is 91.104 N/mm². Further increase of the injection processing temperature lowers the hardness of the material to the value of 90.785 N/mm² recorded at 400°C. As observed the increase in injection processing temperature of the mixture of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type, from 240°C to 270°C leads to a slight increase in the hardness of the material. The maximum hardness is recorded at a temperature of 270°C and it is 90.300 N/mm². Further increase of the injection processing temperature to 280°C lowers the hardness of the material to the value of 90.070 N/mm². It can be observed that at the low processing temperatures (PEEK 90HMF40 - 360°C and PC+PBT Makroblend KU 2-7609 - 240°C), when the mechanical degradation occurs inside the plastification-injection cylinder, in the case of those two polymers tested, the lowest values in hardness is recorded. At the highest processing temperatures (PEEK 90HMF40 - 400°C and PC+PBT Makroblend KU 2-7609 - 280°C) thermal degradation also occurs, which leads to a decrease in hardness of the two polymers. After the impact testing on samples of polyetheretherketone Victrex PEEK 90HMF40 type and the mixture of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type, the following results were obtained regarding the energy

absorbed to break the unnotched samples ( cE ) and

resistance to Izod impact strenght test on unnotched

samples ( iUa ), (Table 2).

In case of polyetheretherketone Victrex PEEK 90HMF40 type the increase of processing temperature from 360°C to 390°C leads to a decrease in hardness from 65.980 kJ/m² to 57.611 kJ/m², while further increase of processing temperature to 400°C leads to an increase in hardness up to a value of 59.136 kJ/m². In case of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type mixture, the increase of processing temperature from 240°C to 280°C leads to an increase in hardness from de 128.420 kJ/m² to 180.900 kJ/m².

After the next tensile test was done on the samples of polyetheretherketone Victrex PEEK 90HMF40 type and mixture of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type, the following results were obtained regarding the necessary force to break the samples (F) and the tensile strength (σ) (Table 3). In the case of polyetheretherketone Victrex PEEK 90HMF40 type, the increase in processing temperature from 360°C to 390°C increases the force required to break the sample from the value of 13714.80 N to the value of 12850.00 N and an increase in tensile strength (σ) from the value of 321.25 MPa to the value of 342.87 MPa. Further increase of processing temperature to 400°C decreases the force required to break the sample and at the same time lowers the tensile strength. In the case of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type mixture, the increase of processing temperature from 240°C to 260°C increases the force required to break the sample from the value of 1766.90 N to the value of 2048.40 N and an increase in tensile strength (σ) from the value of 44.17 MPa to the value of 51.21 MPa. Further increasing of processing temperature to 280°C decreases the force required to break the sample and at the same time lowers the tensile strength. We conclude that the lowest values of tensile strenght are recorded at the lowest and highest processing temperatures. At these extremes temperatures, into the mass of polymers manufactured by injection, mechanical (at the lowest temperature) and thermal (at the highest temperature) degradations may occur, degradations which influence the tensile strenght. 4. TABLES Table 1. Hardnes penetration of polyetheretherketone Victrex PEEK 90HMF40 type and mixture of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type, processed by injection, depending on injection processing temperature

Polyetheretherketone

Victrex PEEK

90HMF40 type

Mixture of polycarbonate

with polybutylene

terephthalate PC + PBT

Makroblend KU 2-7609 type

Processing temperature

[°C]

Type-D Shore

hardness

[N/mm²]

Processing temperature

[°C]

Type-D Shore

hardness

[N/mm²]

360 90.398 240 89.764

370 90.544 250 89.882

380 91.104 260 90.020

390 90.973 270 90.300

400 90.785 280 90.070

Gheorghe Radu Emil Mărieş: Study about the Influence of Processing Temperature on Some Mechanical Properties of the Polyetheretherketone and the Mixture of Polycarbonate with poPlybutylene Terephthalate Using …; Machine Design, Vol.6(2014) No.3, ISSN 1821-1259; pp. 91-96

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Table 2. Izod impact strenght and energy absorbed at the break point of the unnotched samples of polyetheretherketone Victrex PEEK 90HMF40 type and the mixture of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type, depending on the injection processing temperature

Materials

Polyetheretherketone Victrex PEEK 90HMF40

type

Mixture of polycarbonate with polybutylene

terephthalate PC + PBT Makroblend KU 2-7609

type Processing temperature [°C]

cE

[J] iUa

[kJ/m²]

Processing

temperature [°C]

cE

[J] iUa

[kJ/m²]

360 2.639 65.980 240 5.136 128.420

370 2.444 61.124 250 5.896 147.422

380 2.401 60.040 260 6.376 159.400

390 2.304 57.611 270 6.622 165.558

400 2.365 59.136 280 7.236 180.900

Table 3. Necessary tensile force variation on test samples (F) and tensile pull-out strength (σ) for polyetheretherketone Vitrex PEEK 90HMF40 type and the mixture of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type, depending on the processing temperature

Materials

Polyetheretherketone Victrex PEEK 90HMF40

type

Mixture of polycarbonate with polybutylene

terephthalate PC + PBT Makroblend KU 2-7609

type

Processing

temperature [°C]

F [N] σ

[MPa]

Processing

temperature [°C]

F [N] σ

[MPa]

360 12850.0 321.25 240 1766.9 44.17

370 13020.8 325.52 250 1874.0 46.85

380 13128.0 328.20 260 2048.4 51.21

390 13714.8 342.87 270 2002.3 50.05

400 13435.2 335.88 280 1943.3 48.58

5. CONCLUSIONS The changes in mechanical properties have been studied on polyetheretherketone Victrex PEEK 90HMF40 type and the mixture of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type, polymers used for the production of technical items from different industries depending on the injection processing

temperature. The samples of polyetheretherketone Victrex PEEK 90HMF40 type were made at the following injection temperatures: 360°C, 370°C, 380°C, 390°C and 400°C. The samples of polycarbonate with polybutylene terephthalate PC+PBT Makroblend KU 2-7609 type mixture were made at the following injection temperatures: 240°C, 250°C, 260°C, 270°C and 280°C. The samples were injected using an injection mold machine ENGEL CC 100 Type ES 80/50 HL. As a result of the determination of hardness penetration by Shore D-type method with a D-type durometer SAUTER HB/Germany, it is observed that increasing the injection processing temperature results in negligible hardness variation values of the tested polymers. Determination of Izod impact strength properties were carried out on unnotched samples, and tests were performed using a pendulum impact tester, PENDOLO P400 type, HAMMEL make, England. Izod impact strengths values for polyetheretherketone Victrex PEEK 90HMF40 type, decreases with the increase of injection processing temperature, up to a certain minimum value, after which, further increase in processing temperatures leads to an increased level of resistance to shock. In the case of mixture of polycarbonate with polybutylene terephthalate PC+PBT Makroblend 2-7609 type, the increase of injection processing temperature leads to an increase of Izod impact strengths values. Determinations of tensile resistance for the two materials was made with a tensile-test machine WPM-EBV-Thuringer werk, Ranenstein Industry gerat R37, Type 2092. The tensile resistance of those two tested polymers increases with the increase of the processing temperature, up to a certain maximum value, after which, further increase of the processing temperatures leads to a decrease of the values. The highest value of tensile resistance for polyetheretherketone Victrex PEEK 90HMF40 type was recorded at 390°C and had the value of 342.87 MPa, and for the mixture of polycarbonate with polybutylene terephthalate PC+PBT Makroblend 2-7609 type was recorded at 260°C and had the value of 51.21 MPa. The lowest value of tensile resistance was recorded at the lowest temperature of processing. REFERENCES [1] Mărieș, Gh. R. E. (2008). Materiale plastice în

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