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Ethylene-propylene rubbers and elastomers (also called EPDM and EPM) continue to be one of the most widely used and fastest growing synthetic rubbers having both specialty and general-purpose applications. Sales have grown to 870 metric tons (or 1.9 billion pounds) in 2000 since commercial introduction in the early 1960’s. Polymerization and catalyst technologies in use today provide the ability to design polymers to meet specific and demanding application and processing needs.
Typical Areas of Application
Versatility in polymer design and performance has resulted in broad usage in automotive weather-stripping and seals, glass-run channel, radiator, garden and appliance hose, tubing, belts, electrical insulation, roofing membrane, rubber mechanical goods, plastic impact modification, thermoplastic vulcanisates and motor oil additive applications.
Typical Properties
Ethylene-propylene rubbers are valuable for their excellent resistance to heat, oxidation, ozone and weather aging due to their stable, saturated polymer backbone structure. Properly pigmented black and non-black compounds are color stable.
As non-polar elastomers, they have good electrical resistivity, as well as resistance to polar solvents, such as water, acids, alkalies, phosphate esters and many ketones and alcohols.
Amorphous or low crystalline grades have excellent low temperature flexibility with glass transition points of about minus 60 °C.
Heat aging resistance up to 130°C can be obtained with properly selected sulfur acceleration systems and heat resistance at 160°C can be obtained with peroxide cured compounds. Compression set resistance is good, particularly at high temperatures, if sulfur donor or peroxide cure systems are used.
These polymers respond well to high filler and plasticiser loading, providing economical compounds. They can develop high tensile and tear properties, excellent abrasion resistance, as well as improved oil swell resistance and flame retardance. A general summary of properties is shown in Table I below.
Table 1. Properties of ethylene-propylene elastomers.
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Mooney Viscosity, ML 1+4 @ 125 °C
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5-200+
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Ethylene Content, wt. %
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45 to 80 wt. %
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Diene Content, wt. %
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0 to 15 wt. %
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Specific Gravity, gm/ml
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0.855-0.88 (depending on polymer composition)
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Hardness, Shore A Durometer
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30A to 95A
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Tensile Strength, MPa
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7 to 21
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Elongation, %
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100 to 600
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Compression Set B, %
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20 to 60
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Useful Temperature Range, °C
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-50 ° to +160 °
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Tear Resistance
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Fair to Good
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Abrasion Resistance
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Good to Excellent
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Resilience
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Fair to Good (stable over wide temp. ranges)
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Electrical Properties
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Excellent
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* Range can be extended by proper compounding. Not all of these properties can be obtained in one compound.
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