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

三元乙（EPDM）是乙烯、烯和少量非轭二烯烃聚物。

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.

二烯烃和烯基芳烃是非常不稳分，可聚合产生凝。对于给烯烃和烷基芳烃，氢化可以改善产品质量。