Ethylene Propylene Rubber (EPR, EPM)
Properties and Applications
Ethylene propylene rubber (EPR, EPM) is a copolymer of ethylene and propylene. This type of elastomer is very similar to EPDM rubber, but unlike EPDM, EPR does not have any double bonds in the main chain, whereas EPDM rubbers contain small amounts of non-conjugated diene monomers which provide cross-linking sites for vulcanization. EPRs, on the other hand, can only be crosslinked with a peroxide-based cure system or by irradiation with high-energy radiation such as gamma rays or high energy electrons which generate free radicals that induce crosslinking.
EPMs have excellent resistance to heat, oxidation, weather, and ozone. They also exhibit excellent electrical insulation, and low temperature properties, but have only fair
mechanical properties. Their resistance to chemicals is generally good. For example, EPRs are resistant to many polar fluids both protic and aprotic. This includes
most phosphate-ester based hydraulic fluids,
silicone oils and greases, glycol- and silicon-based based brake fluids, sodium and potassium alkalis as well as hot water and steam up to 150°C. However,
EPRs have poor mineral oil and flame resistance.
The largest market for EPRs is the automotive industry. Typical applications include tires, tubes, weatherstrips, O-rings, gaskets, accumulator bladders, wire and cable connectors, and various automotive parts.