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MATERIAL PROPERTIES GUIDE
TABLE OF CONTENTS
Page
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
MATERIAL PROPERTY DATA TABLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
MECHANICAL PROPERTIES Tensile Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Flexural Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Creep Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 Creep Rupture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 Fatigue Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 Impact Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
THERMAL PROPERTIES Heat Deflection Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 Continuous Use Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 Heat Aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
FLAMMABILITY AND COMBUSTION PROPERTIES Flammability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Smoke Emission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Toxic Gas Emission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
ELECTRICAL PROPERTIES Volume Resistivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 Surface Resistivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 Relative Permittivity and Dielectric Dissipation Factor . . . . . . . . . . . . . . . .15
TRIBOLOGY Wear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 Friction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 Limiting Pressure and Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 Environmental Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 Gas Permeation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 Hydrolysis Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 Chemical Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 Radiation Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
INTRODUCTION
Victrex is the sole manufacturer of VICTREX PEEK polymer, the repeat unit that comprises oxy-1,4-phenyleneoxy-1,4-phenylene-carbonyl-1,4-phenylene, as shown in Figure 1. This linear aromatic polymer is semi-crystalline and is widely regarded as the highest performance thermoplastic material currently available. A summary of key physical properties is as follows:
Figure 1: VICTREX PEEK Repeat Unit
HIGH TEMPERATURE PERFORMANCE
VICTREX PEEK and compounds typically have a glass transition temperature of 143°C (289°F) and a melting temperature of 343°C (649°F). Independent tests have shown that VICTREX PEEK exhibits a heat distortion temperature up to 315°C (599°F) (ISO R75, glass fibre filled) and a Continuous Use Temperature of 260°C (500°F) (UL 746B).
WEAR RESISTANCE
VICTREX PEEK has excellent friction and wear properties which are optimised in the specially formulated tribological grades VICTREX 450FC30 and VICTREX 150FC30. These materials exhibit outstanding wear resistance over wide ranges of pressure, velocity, temperature and counterfacial roughness.
CHEMICAL RESISTANCE
VICTREX PEEK has excellent resistance to a wide range of chemical environments, even at elevated temperatures. The only common environment which dissolves VICTREX PEEK is concentrated sulfuric acid.
FIRE, SMOKE AND TOXICITY
VICTREX PEEK is highly stable and requires no flame-retardant additives to achieve a V-0 rating at 1.45 mm
(0.057 in) thickness. The composition and inherent purity of the material results in extremely low smoke and toxic gas emission in fire situations.
HYDROLYSIS RESISTANCE
VICTREX PEEK and compounds are not attacked by water or pressurised steam. Components that are constructed from these materials retain a high level of mechanical properties when continuously conditioned in water at elevated temperatures and pressures.
ELECTRICAL PROPERTIES
The electrical properties of VICTREX PEEK are maintained over a wide frequency and temperature range.
PURITY
VICTREX PEEK materials are inherently pure with exceptionally low levels of ionic extractables and excellent outgassing characteristics.
| VICTREX PEEK PRODUCT RANGE POWDER 150P Low viscosity grade for extrusion compounding. 380P Medium viscosity grade for extrusion compounding. 450P Standard viscosity grade for extrusion compounding. |
|---|
| GRANULES 150G Easy flow grade for injection moulding of thin sections and complex parts (USA only). 450G General purpose grade for injection moulding and extrusion. |
| GLASS FILLED 150GL30 Easy flow, 30% glass fibre reinforced for injection moulding. 450GL30 General purpose, 30% glass fibre reinforced grade for injection moulding and extrusion. |
| CARBON FILLED 150CA30 Easy flow, 30% carbon fibre reinforced for injection moulding. 450CA30 Standard viscosity, 30% carbon fibre reinforced grade for injection moulding. |
| LUBRICATED 150FC30 Easy flow, 30% carbon/PTFE grade for injection moulding. 450FC30 Standard viscosity, 30% carbon/PTFE grade for injection moulding and extrusion. |
| DEPTH FILTERED 381G Medium viscosity for wire coating, capillary tubing, film and monofilament extrusion. 151G Low viscosity monofilament and multifilament extrusion grade. Also suitable for injection moulding of thin wall and complex parts. |
* Results based on VICTREX 450G
3
There are a number of Victrex specialty products that are not listed in the data table. Data sheets for these materials can be obtained from your local Victrex representative.
6
| MECHANICAL PROPER TIES | Figure 3: Tensile Strength Versus Temperature for VICTREX PEEK Materials | ||||||
|---|---|---|---|---|---|---|---|
| VICTREX PEEK is widely regarded as the highest performance material processable using conventional thermoplastic processing equipment. | 300 -148 | -48 VICTREX | 52 | 152 252 Temperature / °F | 352 | 452 | 40000 552 |
450CA30
250
Tensile Strength / MPaFlexural Strength / psi Tensile Strength / psi
10000
TENSILE PROPERTIES
The tensile properties of VICTREX PEEK exceed those of
most engineering thermoplastics. A comparative tensile
plot of VICTREX PEEK materials is shown in Figure 2,
where stress is defined as the applied force divided by
200
150
100
the original cross-sectional area and the strain as the extension per unit length of the sample.
The initial part of each trace in Figure 2 is approximated to be linear and by definition is equivalent to the tensile modulus. Due to the viscoelastic nature of VICTREX PEEK, a range of values for tensile properties may be obtained by testing at different strain rates or temperatures. Therefore, evaluations of the tensile parameters contained in the data table were conducted in accordance with the ASTM D638 testing standard with strain rates set at either 5 or 50 mm min-1 (0.2 or
2.0 in min-1).
Figure 2: Typical Stress Versus Strain Curves for
VICTREX PEEK Materials
300 40000
250 35000 50 00
Flexural strength has been defined as the maximum stress sustained by the test specimen during bending, and flexural modulus as the ratio of stress to strain difference at pre-defined strain values.
The data plotted in Figures 4 and 5 define the exceptional temperature range over which VICTREX PEEK can be used as a structural material. However, flexural strength measurements made above 200°C (392°F) are subject to error as the yield point of these materials is greater than the 5% strain specified in the test standard. Above this value, a linear stress to strain relationship cannot be assumed for the calculation of flexural properties.
30000
200
Stress / MPa
Stress / psi
Figure 4: Flexural Strength Versus Temperature for
VICTREX PEEK Materials
Temperature / °F
25000
20000
150
15000
100
32 132 232 332 432
350
10000
VICTREX 450CA30
5000 300
0
Flexural Strength / MPa
40000
0
0
250
30000
200
150
VICTREX PEEK is used to form structural components
which experience or continually operate at high tem
peratures. Figure 3 shows a plot of tensile strength ver
20000
100
10000
50
sus temperature for VICTREX PEEK materials and
demonstrates a high retention of mechanical properties
over a wide temperature range.
Temperature / °C
FLEXURAL PROPERTIES
VICTREX PEEK and the high-performance compounds based on VICTREX PEEK exhibit outstanding flexural performance over a wide temperature range. Due to the viscoelasticity of these materials, evaluations were performed using a defined deformation rate three point bending test (standards ISO 178 and ASTM D790) with the results plotted versus temperature in Figures 4 and 5.
Figure 7: Tensile Strain Versus Time for VICTREX 450G at 150°C (302°F)
2.0
Tensile Strain / %
1.5
5 MPa (725 psi)
1.0
4 MPa (580 psi)
0.5
0.0 1.E+1 1.E+2 1.E+3 1.E+4 1.E+5 1.E+6 1.E+7 1.E+8
Time / s
Figure 5: Flexural Modulus Versus Temperature for CREEP PROPERTIES VICTREX PEEK Materials Creep may be defined as the deformation observed in a sample versus time under a constant applied stress.
Temperature / °F -148 -48 52 152 252 352 452 VICTREX PEEK has outstanding creep resistance for an
3500000 engineering thermoplastic material and may sustain
large stresses over a useful service life without signifi-
Flexural Modulus / psi
Flexural Modulus / GPa
cant time induced extension. Figures 6 and 7 display
the creep behavior of VICTREX 450G with respect to
applied stress, time and temperature.
The magnitude of stress, time and temperature
required to induce accurately measurable (> 0.5%)
strains is exceptionally large for an unfilled polymer.
500000
Values of creep modulus may be calculated from such
0 data and used as a measure of resistance to creep deformation. The creep moduli for some of the high performance compounds from the VICTREX PEEK grade range are plotted against time in Figure 8.
Figure 6: Tensile Strain Versus Time for Figure 8: Creep Modulus Versus Time for VICTREX 450G at 23°C (73°F) VICTREX PEEK at 23°C (73°F) and 150°C (302°F)
2.0
25
3500000
50 MPa (7250 psi)
3000000
20
1.5
Tensile Strain / %
2500000
Modulus / psi
2000000
1.0
30 MPa (4350 psi)
1500000
20 MPa (2900 psi)
0.5
1000000
5
500000
10 MPa (1450 psi)
0.0 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08
0
0 1E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7 1E+8
Time / s Time / s
From the data in Figure 8 it is clear that reinforcement significantly enhances the excellent creep resistance of VICTREX PEEK and that the carbon fibre based compounds (CA30) are the highest performance materials tested.
If analogous plots to Figures 6 and 7 are constructed for VICTREX 450CA30 (Figures 9 and 10), the time dependent strain behaviour over experimentally practicable lifetimes may be evaluated. From the data shown in Figure 9 it is clear that there is little measurable creep at ambient temperatures even for the highest values of stress [80 MPa (11,600 psi)] applied to the VICTREX
450CA30 samples.
At elevated temperatures (Figure 10), under the same applied stresses, small but measurable time dependent strains are observed. Although the creep resistance of natural VICTREX PEEK is outstanding for an unfilled material, VICTREX 450CA30 can be used to make structural components which will withstand continual loading over a wide temperature range.
Figure 9: Tensile Strain Versus Time for VICTREX 450CA30 at 23°C (73°F)
CREEP RUPTURE
The performance of thermoplastic materials under a constant applied stress may also be considered in terms of creep rupture. Creep rupture indicates the maximum loading a material will sustain for a given period before it fails, where failure is defined as brittle or necking deformation. Figure 11 shows tensile creep rupture data versus time for natural and reinforced VICTREX PEEK materials.
Strain / %
| 1 | |
| 0.8 | |
| 0.6 | |
| 0.4 | 60 MPa (8700 psi) 80 MPa (11,600 psi) |
1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 Time / s
Figure 11 shows that there is little difference between the grades at ambient temperatures over the time-scale tested. Therefore, experiments were performed at elevated temperatures (Figure 12).
40 MPa (5800 psi)
0.2
20 MPa (2900 psi)
0 1E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7
Time / s
Figure 10: Tensile Strain Versus Time for VICTREX 450CA30 at 150°C (302°F)
1
0.8
Tensile Strain / %
0.6
0.4
0.2
50 MPa (7250 psi) 40 MPa (5800 psi) 30 MPa (4350 psi) 20 MPa (2900 psi)
| 0 | ||||||
| 1E+1 | 1E+2 | 1E+3 | 1E+4 | 1E+5 | 1E+6 | 1E+7 |
| Time / s |
1E+0 1E+1 1E+2 1E+3 1E+4 1E+5 1E+6 1E+7 Time / s
Figure 12 shows the effect of fibre reinforcement and orientation for VICTREX PEEK materials. The angles indicate the direction of testing with respect to melt flow. VICTREX 450CA30 exhibits superior creep rupture performance over the other materials tested and to most high performance thermoplastics. Therefore, VICTREX 450CA30 materials are often used to form components which experience permanent loading at high temperatures.
FATIGUE PROPERTIES Figure 14: Charpy Impact Strength Versus Temperature for Fatigue may be defined as the reduction in mechanical VICTREX PEEK Materials properties during continued cyclic loading. In these
1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07
No. of Cycles to Failure and 16 (ASTM D256). Figure 13 clearly shows that the excellent fatigue resis-
tance of VICTREX 450G is enhanced by both glass and
for Various High Performance Materials
carbon fibre reinforcement. Independent studies have shown that these compounds feature the optimum 1200
level of reinforcement for improved fatigue and
mechanical performance.
IMPACT PROPERTIES
Impact testing may be classified according to the ener
gy imparted to the impactor prior to contact with the
Izod Impact Strength / J m-1
1000
800
600
material. Low energy studies are performed using a
pendulum geometry, whereas higher energy failures
are evaluated using falling weight apparatus. The impact properties of a material are strongly dependent on test geometry (notch radius and position), temperature, impact speed and the condition of the sample (surface defects). Therefore, in an attempt to unify these variables, measurements are often made in accordance with one of the testing standards.
400
200
0
VICTREX VICTREX VICTREX PAI + 30% PPS + 40% Polyimide 450G 450GL30 450CA30 Glass Glass
The bar chart shown in Figure 15 allows comparisons to be made between VICTREX PEEK materials and other high performance compounds. Natural VICTREX 450G has the highest unnotched impact strength and remains unbroken under the Izod test conditions.
THERMAL PROPERTIES
Various High Performance Materials
VICTREX PEEK has a glass transition temperature of
120
143°C (289°F) and, because it is a semi-crystalline ther
100
80
60
40
20
PAI + 30% VICTREX VICTREX VICTREX Polyimide PPS + 40% Glass 450GL30 450CA30 450G Glass
moplastic, retains a high degree of mechanical properties close to its melting temperature of 343°C (649°F).
HEAT DEFLECTION TEMPERATURES
The short term thermal performance of a material may be characterised by determining the Heat Deflection Temperature (HDT, ISO 75). This involves measuring the temperature at which a defined deformation is observed in a sample under constant applied stress. A comparative chart of high performance materials using ISO 75 HDT values (Figure 18) for a defined applied stress of 1.8 MPa (264 psi) shows that VICTREX PEEK compounds are superior to the other materials tested.
Izod Impact Strength / J m -1
Figure 16 shows the effects on the impact strength of notching various materials. The geometry of the notch has been shown to be critical to the measured impact strength. Therefore, in component design, moulded
notches or acute angles should be avoided. High Performance Materials
600 500 400 300 200
Temperature / °F
80 70 60 50 40 30 20 10 0
Failure Energy / J
-100 -50 0 50 100 150 200 250 300
Temperature / °C
Figure 17 shows the energy to failure of VICTREX PEEK and compounds versus temperature to failure.
Use Temperature (CUT) otherwise known as the Relative Thermal Index (RTI) as defined by Underwriters Laboratories (UL 746B). This test determines the temperature at which 50% of material properties are retained after a conditioning period of 100,000 hours. The UL RTI rating for natural VICTREX PEEK is charted against other engineering materials in Figure 19 (page 13).
Figure 19: Relative Thermal Index (RTI) for a Range of chemical structure of the VICTREX PEEK is highly stable-High Performance Materials and requires no flame retardant additives to achieve low flammability and ignitability values. The composi
300
tion and inherent purity of VICTREX PEEK results in 500 excellent smoke and toxicity performance.
250
FLAMMABILITY
400
200
Temperature / °C
Temperature / °F
The flammability of a material may be defined as the
300
ability to sustain a flame upon ignition from a high
150
energy source in a mixture of oxygen and nitrogen. The
200
100
recognized standard for the measurement of flamma
100
50
0
0
VICTREX VICTREX VICTREX PPA + PAI + 30% PPS + PES PSU 450G 450GL30 450CA30 33% Glass Glass 40% Glass
HEAT AGING
As part of the Underwriters Laboratories evaluation of the physical performance of polymeric materials with respect to temperature, heat aging experiments are performed. These involve conditioning specimens for a pre-defined time at a constant temperature and subsequently measuring their tensile properties. The retention of these properties is calculated with respect to a control and is used as a measure of the thermal aging performance. The outstanding percentage retention of tensile strength and elongation to break for natural VICTREX PEEK is plotted versus conditioning time in Figure 20.
bility is the Underwriters Laboratories test UL94. This involves the ignition of a vertical specimen of defined geometry and measures the time for the material to self-extinguish. The average time from a repeated ignition sequence is used to classify the material. Natural VICTREX 450G has been rated as V-0 [1.5 mm (0.059 in) thickness] which is the best possible rating for flame retardancy.
SMOKE EMISSION
The current standard for the measurement of smoke produced by the combustion of plastic materials is ASTM E662. This uses the National Bureau of Standards (NBS) smoke chamber to measure the obscuration of visible light by smoke generated from the combustion of a standard geometry sample in units of specific optical density. The test may be carried out with either continuous ignition (flaming) or interrupted ignition (nonflaming). A comparative bar chart of the specific optical density for a range of engineering plastics is shown in Figure 21.
Figure 21: Specific Optical Density for a Range of
Engineering Thermoplastics Measured in Flaming Mode for 3.2 mm (0.126 in) Thick Samples
1000
900 800 700 600 500 400
Specific Optical Density / Ds
300 200 100
Exposure Time / h
FLAMMABILITY AND COMBUSTION PROPERTIES
In a fire, the thermal and chemical environment is changing constantly. Therefore, it is difficult to simulate the conditions experienced by a material in a fire situation. The four commonly accepted variables are flammability, ignitability, smoke and toxic gas emission. The
0
VICTREX PEI Phenolic PTFE PC PSU PS PVC Polyester ABS 450G
The data in Figure 21 show that natural VICTREX PEEK has the lowest value of specific optical density of all the materials tested.
TOXIC GAS EMISSION Figure 22: Volume Resistivity Versus Electrification The emission of toxic gases during combustion of a Time for VICTREX 450G polymer cannot be considered purely as a function of
1E+17
the material. The component geometry, heat release,
conditions of the fire, and the synergistic effects of any
toxic gases affect the potential hazard of the material
in an actual fire situation. VICTREX PEEK, like many
organic materials, produces mainly carbon dioxide and
carbon monoxide upon pyrolysis. The extremely low concentrations of toxic gases emitted have been evalu
ated using the Aircraft Standards (BSS 7239, ATS1000/ABD0031). This procedure involves the com-
Volume Resistivity / Ω cm
1E+16
1E+15
1E+14
1E+13
1E+12
plete combustion of a 100 g (0.22 lb) sample in a 1 m3 (35.3 ft3) volume and subsequent analysis of the
1E+11
toxic gases evolved. The toxicity index is defined as the summation of the concentration of gases present normalized against the fatal human dose for a 30 minute exposure. VICTREX 450G gives a 0.22 toxicity index with no acid gases detected.
ELECTRICAL PROPERTIES
VICTREX PEEK is often used as an electrical insulator with outstanding thermal, physical and environmental resistance.
VOLUME RESISTIVITY
Volume resistance and resistivity values are used as aids
in choosing insulating materials for specific applica
tions. The volume resistance of a material is defined as
the ratio of the direct voltage field strength applied
between electrodes placed on opposite faces of a speci
men and the steady-state current between those elec
trodes. Resistivity may be defined as the volume resis
tance normalized to a cubical unit volume.
volume resistivity of VICTREX 450G is plotted versus temperature in Figure 23. This shows that high values for the volume resistance of natural VICTREX PEEK are retained over a wide temperature range.
Temperature / °F 32 82 132 182 232 282 332 382 432 482 1E+18
1E+17
Volume Resistivity / Ω cm
1E+16
1E+15
1E+14
1E+13
1E+12
1E+11
As with all insulating materials, the change in resistivity with temperature, humidity, component geometry and time may be significant and must be evaluated when designing for operating conditions. When a direct voltage is applied between electrodes in contact with a specimen, the current through the specimen decreases asymptotically towards a steady-state value. The change in current versus time may be due to dielectric polarization and the sweep of mobile-ions to the electrodes. These effects are plotted in terms of volume resistivity versus electrification time in Figure 22.
The larger the volume resistivity of a material, the longer the time required to reach the steady-state current. Natural VICTREX 450G has an IEC 93 value of
6.5 x 1016 Ω cm at ambient temperatures, measured using a steady-state current value for 1000 s applied voltage. Using the same experimental technique, the
1E+10 0 50 100 150 200 250