The banded spherulites of iPP induced by pressure vibration injection molding

Isotactic polypropylene (iPP) samples obtained by pressure vibration injection molding (PVIM) and conventional injection molding (CIM) were studied by polarized-light microscopy (PLM), respectively. It was found that the alternating bright and dark banded spherulites were generated in the transitional region of PVIM parts. It is the first time that the banded spherulites of isotactic polypropylene were observed in polymer processing. What's more, the banded spherulites were proved to be constituted of alpha-form crystal by hot stage polarized-light microscopy (HT-PLM) and wide angle X-ray diffraction (WAXD). Morphology of the banded spherulites was also studied by scaning electronical microscopy (SEM).