Vulcanization kinetics for natural rubber (NR)/ ethylene-propylene-diene rubber (EPDM) blends was studied as a function of the compatibilization, by using an oscillatory disk rheometer. For this study, 2.5 phr of thioacetate- (EPDMTA) or mercapto-modified EPDM (EPDMSH) were employed in blends vulcanized with sulfur/CBS curing system. Both functionalized copolymers increased the curing velocity of the blends, but the higher overall rate was achieved with EPDMSH-modified systems, using the Chough and Chang model. However, when using the Coran model, we observed that they act in distinct vulcanization steps: EPDMSH acts preferentially at the beginning of the curing process whereas EPDMTA increases the rate of the crosslink formation. In addition, EPDMTA decreased the tendency for crosslink decomposition, as indicated by the lower value of reversion degree.
Elastomer blends; natural rubber; vulcanization kinetics; compatibilization
