The effect of functionalized ethylene propylene diene rubber (EPDM) on the kinetics of sulfur vulcanization of normal rubber/EPDM blends

The effect of mercapto- and anhydride-functionalized ethylene propylene diene rubber (EPDM) or ethylene-vinyl acetate (EVA) copolymers on the vulcanization kinetics of natural rubber/EPDM blends was investigated using the oscillatory disk rheometer. The mercapto groups in both EPDM and EVA copolymers resulted in a significant decrease of the curing time. The Coran's model was applied to set the kinetic constants within each distinct step of the vulcanization process. The highest curing velocity was perceived in a blend containing 2.5 phr of mercapto-functionalized EVA. The functionalized EVA, especially that which was functionalized with anhydride groups, also displayed a lower solvent uptake on blending, which would imply an increase of the crosslink density as well a covulcanization phenomenon.