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）是乙烯、丙烯和少量非轭二烯。

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.

二烯和烯基芳是非常不稳定组分，可合产生凝胶。对于给定烯和烷基芳，氢化可以改善产品质量。