Development of Crystalline Morphology, Structure, and Impact Property of Isotactic Polypropylene and Poly(cis-Butadiene) Rubber Blends During Mixing

The development of crystalline morphology, structure, and impact property of isotactic polypropylene (PP) and poly(cis-butadiene) rubber (PcBR) (vol. %: 80/20) blends during mixing were investigated and compared to neat PP. It was found by polarized optical microscopy (POM) and small-angle light scatter (SALS) that the incorporation of PcBR into PP caused small and imperfect PP spherulites and more diffused spherulite boundaries, which sharply exhibited in the initial 2 min of mixing but remained almost unchanged in the rest of the mixing time. Crystalline structure of neat PP and blends was studied by wide-angle x-ray diffraction (WAXD). The addition of PcBR into PP induced formation of PP β-form spherulites. As mixing time developed, the relative degree of crystallization decreased whereas interplanar distance increased. Impact strength of PP and blends was tested. The result showed that impact strength of blends significantly improved with increase of the mixing time.