Three Yuan second grade third rubbers (EPDM) is the ethylene, the propylene and the few non-conjugate diolefin copolymer.

三元乙丙橡胶（EPDM）是乙、丙少量二的聚物。

The diolefins and alkenyl aromatics are very unstable components which can give gums by polymerization.In giving olefins and alky aromatics the hydrogenation improves the product quality.

二基芳是常不稳定的组分，可聚合产生凝胶。对于给定烷基芳，氢化可以改善产品质量。