EPDM material — a guide for O-ring seals
EPDM (ethylene-propylene-diene rubber) is the go-to choice for water, steam, brake fluid and outdoor applications. Properties and limitations.
- Published:
- Author:
- Ing. Filip Meheš
- Category:
- Materials
- Material:
- EPDM
EPDM is a terpolymer of ethylene, propylene and a diene monomer. Its fully saturated polymer backbone gives it exceptional resistance to ozone, UV radiation, oxygen and ageing — which is why it is the default choice for outdoor seals, roofing membranes and automotive window weatherstrips.
Key EPDM properties
EPDM handles continuous temperatures from -40 °C to +130 °C, briefly up to +150 °C; peroxide-cured grades have higher heat resistance than sulphur-cured ones. It excels with hot water and steam (including condensate), glycol-based brake fluid (DOT 3, DOT 4, DOT 5.1), dilute acids and bases, and polar solvents like alcohol and ketones.
EPDM's biggest limitation is extremely poor resistance to mineral oils, fuels and hydrocarbons. For oil-hydraulic applications EPDM is unsuitable — a swollen seal loses all function. Always verify chemical compatibility before specifying it.
Typical applications
EPDM is used in potable and process water lines, steam systems, sanitary equipment, automotive brake systems, HVAC (note: EPDM is not suitable for R134a refrigerant and refrigeration circuits — HNBR is the standard for AC-system seals), and as window, door and outdoor enclosure seals. For the water + outdoor combination, EPDM is the clear pick over NBR or silicone.