| Property | Value |
|---|---|
| Temperature range | -20 °C to +150 °C |
| Hardness | 50–90 Shore A |
| Best at | Hot petroleum oil, heat aging, ozone |
| Contains fluorine | No |
The gap between nitrile and FKM
Nitrile is the default oil rubber and it runs out of heat resistance around 100 to 120 °C in continuous service. FKM handles 200 °C and costs several times more. Between those sits a large population of automotive and industrial parts running at 130 to 150 °C in oil, and ACM is the family built for that band. Specifying FKM for those parts works and overpays; specifying nitrile fails in the field.
It also resists ozone and heat aging well, so a part in an engine bay is not fighting the environment outside the oil either.
How we compound and test it
ACM uses cure systems that are more sensitive than a standard sulfur cure and typically needs a post-cure to develop full properties and to drive off residuals. Skipping or shortening the post-cure produces a part that passes a dimensional check and then shows high compression set in service, which is the failure that looks like a design problem and is actually a process one.
We run compression set at the service temperature rather than at a standard 100 °C, because for this family the whole point is behaviour at the top of the range.
The two mistakes buyers make
The first is water. ACM hydrolyses. Coolant, steam, or a wash-down environment will break it down, and a seal that sees both oil and water is not an ACM part regardless of the temperature.
The second is cold. At -20 °C it is already stiff, and below that it is effectively rigid. A vehicle part that has to seal on a cold start in a northern winter needs a different family or a modified grade, and that has to be established before tooling.
Typical uses
- Transmission and engine oil seals
- Shaft seals in hot petroleum oil
- O-rings and gaskets in the 130–150 °C oil band
- Automotive parts where FKM is over-specified
- Hot oil service away from water and coolant