EPDM rubber

EPDM rubber (ethylene propylene diene monomer rubber)^[1][2][3] is a type of synthetic rubber that is used in many applications.

EPDM is an M-Class rubber under ASTM standard D-1418; the M class comprises elastomers with a saturated polyethylene chain (the M deriving from the more correct term polymethylene). EPDM is made from ethylene, propylene, and a diene comonomer that enables crosslinking via sulfur vulcanization. Typically used dienes in the manufacture of EPDM rubbers are ethylidene norbornene (ENB), dicyclopentadiene (DCPD), and vinyl norbornene (VNB). Varying diene contents are reported in commercial products, which are generally in the range from 2 to 12%.^[4][5]

The earlier relative of EPDM is EPR, ethylene propylene rubber (useful for high-voltage electrical cables), which is not derived from any diene precursors and can be crosslinked only using radical methods such as peroxides.^[6]

As with most rubbers, EPDM as used is always compounded with fillers such as carbon black and calcium carbonate, with plasticisers such as paraffinic oils, and has functional rubbery properties only when crosslinked. Crosslinking mainly occurs via vulcanisation with sulfur but is also accomplished with peroxides (for better heat resistance) or phenolic resins. High-energy radiation, such as from electron beams, is sometimes used to produce foams, wire, and cable.