Hydraulic Piston EPDM Orings
Ethylene propylene diene monomer (EPDM) is a copolymer of ethylene, propylene and a small amount of non-conjugated diene monomers (3 – 9 percent) which provide cross-linking sites for vulcanization:
The diene is usually dicyclopentadiene, ethylidene nobornene, or 1,4 hexadiene. These terpolymers can be vulcanized by traditional techniques.
EPDM elastomers have excellent heat, ozone/weathering, and aging resistance. They also exhibit excellent electrical insulation, compression set, and low temperature properties, but only fair physical strength properties. Their resistance to chemicals is generally good. For example, EPDMS’s are resistant to many polar fluids, hot water and steam up to 200°C (in the absence of air). In fact, EPDMs are probably the most water resistant rubbers available. However, they are not compatible with mineral and synthetic di-ester lubricants, and hydrocarbon fuels and solvents. They also have poor flame resistance.
Important manufacturers and suppliers of EPDM rubbers are Dow Chemical, ExxonMobil, and Lion Elastomers.
The largest market for EPDMs is the automotive industry. Typical applications include radiator and heater hoses, window and door seals, O-rings and gaskets, accumulator bladders, wire and cable connectors and insulators, diaphragms, and weather stripping.
Furthermore, blends of EPDMs and other polymers (PP) are used for car bumpers, fender extensions, and rub strips.
Other major applications are roofing and waterproofing, such as bitumen modifications, facade and parapet sealants, expansion joints, and pool- and tankliners.
The typical working temperature range is -45°C to +150°C (-50°F to +300°F) and up to +180°C (+355°F) in steam.