Novel Dynamically Vulcanized Elastomer-Polypropylene Blends with Improved Elasticity

Abstract

Abstract High elasticity in dynamically vulcanized EPDM-Polypropylene blends, as demonstrated by lower residual deformation upon release of constraint, is a much desired attribute. It has been found that this property can be improved beyond the conventional norms of highly crosslinking the rubber phase. This is achieved through the use of a polypropylene phase with a high degree of long-chain branching. The branching index, g', at molecular weight greater than 1×106 should be less than about 0.6. It is postulated that in the melt and at low frequencies the long-chain branched polypropylene behaves as a network. Therefore in the melt, the dynamically vulcanized alloy behaves as a dual network material: one network being the chemically crosslinked rubber phase, and the other being the physical network arising from the high level of long-chain branching in polypropylene. In the solid state, the co-continuous morphology arising from the choice of long-chain branched polypropylene contributes to the enhanced elasticity of the dynamically vulcanized thermoplastic elastomer.