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

ABSTRACT 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. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47442.