EPDM rubber (ethylene propylene diene Monomer (M-class) rubber),
a type of synthetic rubber, is an elastomer which is characterized
by a wide range of applications. The E refers to Ethylene, P to Propylene,
D to diene and M refers to its classification in ASTM standard D-1418.
The "M" class includes rubbers having a saturated chain
of the polymethylene type. The diene(s) currently used in the manufacture
of EPDM rubbers are DCPD (dicyclopentadiene),
ENB (ethylidene norbornene) and VNB (vinyl norbornene).
A roll of EPDM foil, used for waterproofing roofsThe ethylene content is
around 45% to 75%. The higher the ethylene content the higher
the loading possibilities of the polymer, better mixing and extrusion.
Peroxide curing these polymers give a higher crosslink
density comparedwith their amorphous counterpart.
The amorphous polymer are also excellent in processing.
This is very much influenced by their molecular structure.
The dienes, typically comprising between 2.5 wt%
up to 12 wt% of the composition serve as crosslinks when curing
with sulphur and resin, with peroxide cures the diene (or third monomer)
functions as a coagent, which provide resistance to unwanted tackiness,
creep or flow during end use.
EPDM rubber is used in vibrators
and seals; glass-run channel; radiator, garden and appliance hose; tubing; washers; belts; electrical insulation, and speaker cone surrounds. It is also used as a medium for water resistance in electrical cable-jointing, roofing membranes, geomembranes, rubber mechanical goods, plastic impact modification, thermoplastic, vulcanizates, and many other applications.
EPDM exhibits satisfactory compatibility with fireproof hydraulic fluids, ketones, hot and cold water, and alkalis, and unsatisfactory compatibility with most oils, gasoline, kerosene, aromatic and aliphatic hydrocarbons, halogenated solvents, and concentrated acids.
The main properties of EPDM are its outstanding heat, ozone and weather resistance. The resistance to polar substances and steam are also good. It has excellent electrical insulating properties.
Typical properties of EPDM vulcanisates are given below. EPDM can be compounded to meet specific properties to a limit depending first on the EPDM polymers available, then the processing and curing method(s) employed. EPDMs are available in a range of molecular weights (indicated in terms of Mooney viscosity ML(1+4)@125°C), varying levels of ethylene, third monomer and oil content.