Ethylene-vinyl acetate (EVA) copolymers with different amounts of vinyl acetate have been functionalized with mercapto groups and these reactive compounds were used as compatibilizing agent for nitrile rubber (NBR)/ ethylene-propylene-diene rubber (EPDM) blends. The effects from the structural properties of mercapto-modified EVA compounds on the vulcanizing characteristics, mechanical properties, aging resistance and dynamic-mechanical properties were investigated. The addition of low amounts of mercapto-modified EVA resulted in a decrease of curing time. The functionalized copolymer obtained through transesterification reaction between mercaptoacetic acid and EVA (EVASH) presented better compatibilizing action than that obtained from esterification of hydrolyzed EVA and mercaptoacetic acid (EVALSH). Blends compatibilized with the former compound presented better mechanical performance and more refined morphologies. Finally, aging resistance was improved by the use of mercapto-modified EVA.
Elastomer blends; reactive compatibilization; nitrile rubber; EPDM; EVA copolymer
