Influence of Processing History and Composition on the Basic Structure and Biaxial Deformation Behavior in Dynamically Vulcanized PP/EPDM Blends

Abstract

Abstract Thermal, crystallographic and mechanical properties of unvulcanized and dynamically vulcanized polypropylene/ethylene—propylene—diene monomer rubber (PP/EPDM) thermoplastic elastomer blends were investigated. In these high PP content blends, PP forms the continuous phase. The crystalline regions of the PP is mostly in alpha crystalline form with a small fraction of beta. The additives were found to suppress the beta fraction formation. The results indicate that the PP phase maintains its integrity up to the blend concentrations containing 20% EPDM. Beyond this concentration, the unit cell structure was found to become enlarged in its basal plane. This is also manifested in other properties as the melting point began a significant decrease at this concentration level. Interestingly, the film processability greatly improved beyond this 80/20 concentration and the temperature range, over which uniform films were obtained, was significantly enlarged as a result of reduction of neck formation. This was attributed to the formation and homogeneous distribution of large numbers of micronecks in the PP phase, nucleated by the presence of rubber regions.