EPDM (ethylene propylene diene monomer) is a synthetic rubber built from ethylene, propylene, and a small amount of diene monomer that enables sulfur vulcanization. Because its polymer backbone is fully saturated, EPDM does not contain the carbon-carbon double bonds that make many other rubbers vulnerable to attack by oxygen, ozone, and UV light.
Key properties
The saturated backbone gives EPDM outstanding resistance to weathering, ozone, and ultraviolet exposure, which is why it performs well in parts that stay outdoors or are otherwise exposed to sunlight and atmospheric conditions for years.
EPDM also has good resistance to hot water, steam, and many polar fluids such as brake fluid and diluted acids or alkalis, and it maintains flexibility across a wide temperature range.
Its main limitation is poor resistance to mineral oils, fuels, and most hydrocarbon-based lubricants, which tend to cause EPDM to swell and lose mechanical properties over time.
Typical applications
EPDM is a common choice for automotive weatherstripping and seals, HVAC gaskets, roofing membranes, and outdoor-facing components such as rubber bellows, expansion joints, and protective covers on machinery that operates outside or in wet, dusty environments.
In hydraulic and pneumatic systems, EPDM bellows are frequently specified specifically for their resistance to ozone cracking and weathering, provided the surrounding fluids are compatible (i.e. not oil- or fuel-based).
Things to confirm before specifying
Exact hardness, tensile strength, elongation, and compression set values vary by compound formulation and curing system, so production-specific datasheets should always be used for engineering decisions rather than general reference ranges.
If the application involves contact with oils, fuels, or hydrocarbon-based greases, a different elastomer (such as NBR or FKM) is usually a better fit than EPDM.