STRENGTH ENHANCEMENT FROM HETEROGENEOUS NETWORKS OF ETHYLENE–PROPYLENE/ETHYLENE–PROPYLENE–DIENE

Abstract

Abstract Random copolymers of ethylene and propylene are usually miscible with the corresponding unsaturated terpolymer (EPDM). Vulcanization of these blends yields networks in which only the EPDM is cross-linked. Despite chemical modification of the EPDM by its reaction with sulfur, there is no phase-separation evident during curing. The blend exhibits substantially higher strength than the corresponding pure EPDM networks, when compared at equal modulus. Thus, nearly miscible blend networks having a large disparity in component cross-linking can circumvent the usual trade-off between the stiffness and strength of elastomers. This exemplifies a general route to better mechanical properties via blends having a homogeneous phase morphology and whose components have substantially different cross-link densities.