Ethylene and termonomer content

EPDM grades with high ethylene content behave more like a thermoplastic and can be more easily mixed, extruded and calendered. They give higher tensile strength values and therefore tolerate correspondingly higher filler and plasticizer loadings. Additionally, they impart higher hardness and elongation.

The content of non-conjugated diene (termonomer) influences especially the rate of cure (scorch time, cure time), compression set and the stress-strain behavior.

In continuous vulcanization processes (UHF, LCM, hot air, Ballotini) where sulfur is used as a curative, highly unsaturated EPDM grades are chosen to obtain as fast a cure rate as possible in order to provide high quality end products at high output rates.

In discontinuous processes, on the other hand, medium unsaturated grades are generally used, because here cure times can be reduced more effectively by increasing the cure temperature (autoclave, compression molding) or the processing temperature / injection rate (in injection molding).

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