Styrene–butadiene Rubber/Epoxidized Natural Rubber Blends: The Effect of Vulcanization System on Blends Properties

The dynamic properties, curing characteristics, and swelling behavior of the blends cured using two types of vulcanization systems [i.e., conventional vulcanization (CV) and semiefficient vulcanization (semi-EV)] were investigated. Results indicate that the maximum elastic torque (S′ @MH) and the torque difference, S′ @MH–S′ @ML (maximum elastic torque minus minimum elastic torque) increased with the increasing epoxidized natural rubber (ENR) composition in the blend. However, a reverse trend was observed for tan δ @MH and viscous torque (S″ @MH). At a similar blend ratio, the CV system gives a higher S′ @MH and torque difference but a lower tan δ @MH and S″ @MH than the semi-EV system. The scorch time, t 2 and cure time, t 90, decreased with increasing ENR composition in the blends. Semi-EV system blends exhibit shorter t 2 and t 90 than CV system blends. The swelling degree decreased with increasing ENR composition in the blends and the CV system blends show better oil-swelling resistance.