Plastic Properties Tables

The rating that appears in this table refers to the wear properties of the material in a bearing or bush application, and is normally tested using a Pin-on-Disc wear test. It should be noted that this data does not refer to the abrasion properties of the material, which is normally tested by using a Sand-Slurry test, which provides the abrasion resistance of the material when particles rub or slide over the material. The plastic wear resistance chart ranks our materials out of 20 = best wearing. This comparison is done at ambient conditions. It is important to note that at elevated Temp different products may perform differently in respect to the ranking shown here. Refer to Dotmar technical staff for assistance.

This comparative index should be considered only as roughly indicative. There are too many variables including chemical type, concentration, temperature and contact time. Even the internal stress level of plastic parts can influence the degree of Chemical Resistance and your choice of material. Inorganic Acids, bases and salts are used in a variety of concentrations, as mixtures, or on their own. For pure solutions and mixtures the pH value of the solution is a reliable tool when assessing the chemical resistance of semi-crystalline plastics. Specific Chemical Resistance information and charts are available – Please contact your local Dotmar branch for more information 1800 170 001. 20 = best resistance.

The coefficient of friction of a material is the measure of the sliding resistance of a material over another material. In the case of thermoplastics the mating part is normally steel. When multiplying the co-efficient of friction by the perpendicular force between the two mating sliding faces, this result is the force required to slide the components across each other. Our ranking compares this "surface slipperiness" across our range of materials and is important when selecting products for use in dynamic applications.

This can be measured in two categories (a) short time exposure (a few hours) and (b) continuous use over a period of 5000 /20,000 hours. Our index compares material performance in category (b). After these periods there is a decrease in tensile strength compared to original value. As with all thermoplastics the maximum service temperature also depends on the duration and magnitude of mechanical stresses on the material in application.

Our comparison index on Impact Resistance ranks the materials out of 20 = best. The performance comparison is done at the 'most unfavourable' conditions for each material. In practice this may be harsh on some of the rankings. Impact strength decreases with decreasing service temperature. The minimum service temperature in turn being limited by the extent to which the material is subjected to Impact. Therefore materials ranked differently here at their minimum service temperature may rank very similarly for impact at their maximum service temperature in normal conditions.

The index is a nominal ranking out of 20 = best. Different machining processes using CNC or Manual metal-working or wood-working machinery is suitable for most thermoplastics. Because of the poor thermal conductivity and low melting point of thermoplastics heat generation must be kept to a minimum. Points to note:

• Machining Forces - lower than for metals, lower clamp forces required, lower rigidity therefore support may be needed to prevent deflection in some cases.
• Tools - Keep sharp, ensure only the cutting edge contacts material, and ensure good swarf removal.
• Coolants - Soluble oil types are generally suitable if required. Use only pure water or compressed air for PC, PEI, and PSU.

  Product	Product Type	Value
  Ertalyte	PETP Polyester	20
  Ertacetal C	Acetal	20
  Ertayle TX	PETP Polyester	20
  Tetco V	PTFE Polytetrafluoroethylene	19
  Tetron S	PTFE Polytetrafluoroethylene	19
  Polystone Ultra	PE Polyethlyene	18
  Polystone 7000	PE Polyethlyene	18
  Polystone 7000SR	PE Polyethlyene	18
  Polystone 8000+	PE Polyethlyene	18
  Polystone M-Flametech AST	PE Polyethlyene	18
  Polystone M-Slide	PE Polyethlyene	18
  Ketron PEEK-1000	PEEK Polyetheretherketone	16
  Ertalon 66SA	Nylon	16
  Ertalon 6PLA	Nylon	16
  Nylatron 703XL	Nylon	16
  Ertalon 4.6	Nylon	16
  Nylatron GS	Nylon	16
  Nylatron GSM	Nylon	16
  Nylatron MC901	Nylon	16
  Ertalon LFX	Nylon	16
  Playtec	PE Polyethylene	16
  Polystone 300	PE Polyethylene	16
  Polystone 500	PE Polyethylene	16
  Ertalon 6XAU+	Nylon	16
  Duratron PBI	PBI Polybenzimidazole	16
  Duratron T5530 PAI	PAI Polyamide-imide	16
  Polystone Ezyslide 78	PE Polythylene	16
  Symait PVDF	PVDF Polyviylidenefluoride	16
  Duratron T4301 & T4501 PAI	PAI Polyamide-imide	16
  Duratron T4203 & T4503 PAI	PAI Polyamide-imide	16
  Tetron LG	PTFE Polytetrafluoroethylene	16
  PPSU-1000	PPSU Polyphenylenesulphone	15
  PSU-1000	PSU Polysulphone	15
  Ketron PEEK-HPV	PEEK Polyetheretherketone	15
  PEI-1000	PEI Polyetherimide	15
  Tetron G	PTFE Polytetrafluoroethylene	15
  Techtron HPV PPS	PPS Polyphenylene Sulphide	15
  Tetron HG	PTFE Polytetrafluoroethylene	14
  Ketron PEEK-GF30	PEEK Polyetheretherketone	13
  Ertalon	Nylon	13
  Ketron PEEK-CA30	EK Polyetheretherketone	13
  Tetron GR	PTFE Polytetrafluoroethylene	12
  Ertalon 6SA	Nylon	12
  Trovidur EN PVC	PVC Polyvinylchloride	12
  Tetron G	PTFE Polytetrafluoroethylene	12
  Polystone PP	PP Polypropylene	12
  Tetron C	PTFE Polytetrafluoroethylene	11
  Polycarbonate	PC Polycarbonate	8
  Tetron B	PTFE Polytetrafluoroethylene	7

  
  

This chart compares the "Coefficient of linear thermal expansion" shown as a factor m/m.k in the table. All materials expand with changes in Temperature. Thermoplastics expand considerably more than metals (e.g. Carbon Steel 10.8 (10)-6 compared to UHMWPE 200 (10)-6 ie. approximately 10 times more).

Linear thermal expansion means the product will expand in all directions and this needs to be allowed for in design calculations. The calculation is: (given factor) x 10-6 x length x change in temperature °C.

Engineering thermoplastics vary in their tensile strength. The method for testing the tensile strength of plastics is the same as that of metal; using a "Dog-Bone" test specimen, and recording the yield point.

Things to note when considering tensile or compressive strength – temperature, duration, speed, load and structural requirements. (Strength reduces as temperature increases, strength reduces as duration is extended.)

Some grades of engineering plastics have exceptional impact resistance and very good load carrying capacity. However the performance of materials can be greatly compromised by incorrect design and machining parameters that result in sharp corners on finished parts.

A sharp corner on a machined part can be a "weak" point where cracking will most likely occur. Sharp corners not only reduce the impact resistance of a part, but also allow for stress concentration to occur at that point. This will result in premature failure on load carrying plastic parts.

Following correct design and machining guidelines is imperative, and even though minimising sharp corners may make the machining operation more difficult, it is crucial to long term application success.

Edges of sheet materials used in glazing applications (eg. PC - Makrolon Polycarbonate) must also be free of sharp notches or cracks. Parts machined with sharp corners could eventually stress crack. Rounded corners are correct parameters for machining.

Dotmar offer in-house technical support and thermoplastic applications advice. For correct design and machining guidelines contact our technical experts.

The Flammability Oxygen Index is an economical and precise quality control test of combustible materials. The technique measures the minimum percentage of oxygen in the test atmosphere that is required to support combustion.

Certain thermoplastics are good electrical insulators and offer freedom of design in electrical applications. This table is an indication of which engineering plastic will offer the best or worst performance when used in applications where electrical insulating properties is required.

Please refer to the Technical section of the Dotmar website for explanations of the electrical properties of thermoplastics or contact Dotmar if you require specific technical data.

• - Volume resistivity
• - Surface resitivity
• - Dielectric constant
• - Dielectric strength
• - Dissipation factor
• - Arc resistance

Please note: Electrical properties may also be changed by environmental conditions such as moisture and/or temperature.

The behaviour of materials subjected to repeated cyclic loading in terms of flexing, stretching, compressing or twisting is generally described as fatigue. Such repeated cyclic loading eventually constitutes a mechanical deterioration and progressive material degradation. Failure life is defined as the number of cycles of deformation required to bring about the failure of the test specimen under a given set of oscillating conditions.

Fatigue data are generally reported as the number of cycles to fail at a given maximum stress level. At high stress levels materials tend to fail at lower number of cycles and at low stresses the materials can be stressed cyclically for a greater number of times and in some cases the failure point is virtually impossible to establish.

Two basic types of tests have been developed to test fatigue behavior in thermoplastics:

• - Flexural Fatigue Test
• - Tensile Fatigue Test

For more information on Fatigue Resistance and Plastics, please contact your nearest Dotmar Technical Representative.

Density is calculated by dividing the mass of the material by the volume and is normally expressed in g/cm3. Specific Gravity (SG) is defined as the ratio of density of the material to the density of water (1 g/cm3) at a specified temperature.

A Specific Gravity of less than 1 means that the material will float in water.

Thermoplastics can be subject to degradation if environmental factors are not taken into account. Environmental conditions that could be damaging to plastics include exposure to UV, moisture, chemicals, temperature and oxidation. Not all grades of thermoplastics are suitable for outdoor applications. Materials that are not UV stable will change both in appearance and molecular structure when exposed to UV, and over time can become brittle, crack, change colour, warp etc.

Careful consideration should be taken to ensure correct material selection for not only the application but also the environment in which the material is expected to perform.

• - How long will the material / part be expected to last?
• - To what extend or time period will the material / part exposed to UV? (eg. direct UV early morning/late afternoon or longer periods of exposure during the high risk UV times of the day.) What other environmental factors impact on the application?
• - Exposure to other harsh environmental factors, (eg. water, temperature extremes, chemicals etc.) can impact on overall material performance and contribute to degradation.

This table is a quick guide to assist with product suitability under normal working conditions with exposure to direct sunlight. If you have any questions about environmental effects on thermoplastics, please contact your nearest Dotmar office for assistance.

(Standard grades of thermoplastics can be modified with UV stabilisers to increase UV resistant properties.)

Creep resistance can be defined as a material's ability to resist any kind of distortion when under a load over an extended period of time. For optimum performance and maximum lifetime, engineering plastics, which are subjected to long-term loading, should have a high creep resistance (ie. low plastic deformation under load).

Creep behaviour is also one of the factors that limit the maximum application temperature of a material. This table is an indication of which engineering plastic offer the best or worst performance, with 1 = Best in terms of Creep Resistance.