Effects of montmorillonite on structures and properties of injection-molded polypropylene

A nanocomposite of polypropylene with montmorillonite (PP-MMT) was prepared via melt blending. The structures and properties of PP-MMT were studied by differential scanning calorimetry, polarized optical microscopy, transmission electron microscopy (TEM), and wide-angle X-ray diffraction (WAXD). The orientation behaviors of both MMT and PP in an injection-molded specimen were revealed by TEM and WAXD. The results indicate that the specimen displays a multilayer structure: in the inner layer, the long axes of MMT stacks are parallel to the transverse direction (TD) of the specimen and the b-axes of PP crystallites are perpendicular to the TD; whereas in the outer layer, the long axes of MMT are perpendicular to the TD and the b-axes of PP crystallites are parallel to the TD. The orientation of PP crystallites in PP-MMT is much lower than that in pure PP, which results in lower molding shrinkage of PP-MMT. Structure-property relationship of PP-MMT was discussed with a conclusion that a moderate improvement in performances of PP-MMT might be derived from the intercalated dispersion and special orientation of MMT stacks. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47442.