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、丙少轭二烃的聚物。

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.

二烃芳烃是常不稳定的组分，可聚合产生凝胶。对于给定烃烷芳烃，氢化可以改善产品质。