EPDM is a copolymer of ethylene and propylene, and further a terpolymer of ethylene and propylene with a small amount of a third monomer (often diolefin) to permit vulcanization with sulfur. Ethylene Propylene rubber has excellent resistance to ozone, sunlight and weathering. At low temperatures it has excellent flexibility and resistance to a variety of chemicals (dilute acids, alkalis and polar solvents) as well as good electrical insulation properties.
Cure system – Sulfur Cured vs. Peroxide Cured
EPDMs are usually sulfur cured. Sulfur cured compounds give better flexible properties but are more predisposed to harden and poorer compression set with high temperature. Peroxide cured EPDMs give better heat resistance and lower compression set. It can withstand long term usage especially for hose systems of the construction industry, however, the sulfur cured EPDM is more expensive to produce than the sulfur cured ones.
Other Common Variations
- Often internally lubricated to facilitate installation and reduce friction in dynamic applications.
- Can be formulated using only “white list” ingredients as specified in 21.CFR 177.2600 for use when the elastometer will be in contact with food or beverages.
- Can be submitted for approval by the national sanitation foundation (NSF) for drinking water applications.
- Often used in automotive air conditioning to seal against R134a, R744 refrigerant gas and POE or PAG lubricants.
- Often used in phosphate ester type hydraulic fluids.
ASTM D 1418 Designation: EPM, EPDM
ISO/DIN 1629 Designation: EPM, EPDM
ASTM D2000 / SAE J 200 Codes: AA, BA, CA, DA
Standard Color(s): Black
Hardness Range: 30 to 90 Shore A
Relative Cost: Low
Standard Low Temperature: -55°C / -67°F
Standard High Temperature: 125°C / 257°F
Special Compound Low Temperature: -55C / -67°F
Special Compound High Temperature: 150°C / 302°F
|Performs well in||Does not perform well in|
|Alcohols||Aliphatic and aromatic hydrocarbons|
|Automotive break fluid||Di-ester based lubricants|
|Dilute acids and alkalis||Petroleum based oils and grease|
|Silicone oils and greases|
|Steam over 150°C (300°F)|
|Phosphate ester based hydraulic fluids – Skydrol®|
|Ozone, aging and weathering|