ethylene-propylene rubber (EPM and EPDM) - synthetic rubber: EPM is a polymer of ethylene and propylene; EPDM is a polymer of ethylene and propylene with a small amount of a third monomer (usually a diolefin) to permit vulcanization with sulfur. EPM and EPDM possess excellent resistance to ozone, sunlight, and weathering, have good flexibility at low temperatures, and good electrical insulation properties. Used in the manufacture of tires, hoses, auto parts, coated fabrics, and electrical insulation.