| Property | Value |
|---|---|
| Temperature range | -50 °C to +150 °C, higher in steam with a peroxide cure |
| Hardness | 40–90 Shore A |
| Petroleum oil and fuel | Not compatible, at any grade |
| Contains fluorine | No |
Why it survives outdoors when nitrile does not
It comes down to EPDM's saturated backbone. Ozone attacks carbon-carbon double bonds, and EPDM has none in the main chain, so the cracking that splits a stressed nitrile part outdoors has nowhere to start. The resistance comes from the polymer itself rather than an additive, which is why EPDM weather seals last decades in sunlight while a nitrile equivalent fails in seasons.
The same saturation is why petroleum oil destroys it. EPDM is a non-polar hydrocarbon and so is mineral oil, so the oil is absorbed rather than repelled and the part swells, softens, and loses all sealing force. There is no EPDM grade that resists oil. If oil is present, this is the wrong family, and no amount of compounding will fix it.
Cure system changes what you get
| Cure | Strengths | Where it is chosen |
|---|---|---|
| Sulfur | Lower cost, better tear strength, faster cure | General weather sealing, static gaskets, cost-driven parts |
| Peroxide | Much lower compression set, higher continuous temperature, better steam resistance | Steam and hot-water service, long-life seals, anything held under compression at temperature |
A peroxide-cured EPDM in steam is a genuinely different material from a sulfur-cured one, and the difference shows up as compression set after months in service rather than on an incoming inspection. When a customer describes a seal that sealed fine at install and leaked a year later in hot water, the cure system is the first thing we look at.
Typical uses
- Weather seals, glazing gaskets, and outdoor and roofing components
- Steam and hot-water seals, with a peroxide cure
- Brake systems, where the fluid is glycol-based rather than petroleum
- Coolant and radiator hose components, and washer and dishwasher seals
- Electrical insulation, where its dielectric properties are good
What we do with it here
We mix EPDM in-house and choose the cure system against the service condition rather than defaulting to the cheaper one. Compression-set behaviour is measured in our accredited lab, which is where a sulfur-versus-peroxide decision gets settled with a number instead of an argument.