Dependence of microstructure and properties of polypropylene/bromo-isobutylene-isoprene rubber thermoplastic vulcanizates on the molding process

To explore the dependence of the microstructure and properties of thermoplastic vulcanizates (TPVs) on the molding process. The polypropylene/bromo-isobutylene-isoprene rubber thermoplastic vulcanizates (PP/BIIR-TPVs) are molded by high rate shear injection and compression molding, and the phase morphology and physical-mechanical properties of PP/BIIR-TPVs specimens are investigated. Detailed small-angle X-ray scattering, scanning electron microscopy and atomic force microscopy investigations demonstrate that the high rate shear of injection molding not only decreases the size of BIIR particles but also induces the orientation of the PP matrix and further increases its crystallinity. Subsequently, the PP/BIIR-TPVs molded by injection molding have higher tensile strength and Young's modulus, while the compression molding benefits to higher elongation at break. The mechanism regarding the effects of high rate shear during injection molding on phase morphology development of PP/BIIR-TPVs is discussed. This study guides the preparation of TPVs products with desired properties.