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

三元丙橡（EPDM）烯、丙烯和少量非轭二烯烃的聚物。

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.

二烯烃和烯基芳烃非常的组分，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。