Yasuharu Fukui

The effect of talc on the crystallization of isotactic polypropylene

Isotactic polypropylene (iPP) has been crystallized in the presence of talc under the quiescent state and shear flow of injection molding. The resulting morphology has been investigated by means of polarizing microscopy, transmission electron microscopy, and wide angle X-ray diffraction. In the quiescent state, the iPP lamellae grew from the surface of talc and the transcrystalline region was formed at the interface between iPP melt and the talc. The nucleation of iPP was very frequent on the cleavage plane of talc. The X-ray diffraction pattern of the transcrystal showed a*-axis orientation to the crystal growing direction. In injection-molded samples of the talc-filled iPP, the morphology of lamella growing from talc appeared as same as that of the transcrystal. However, the crystalline orientation of injection-molded talc-filled iPP, in which the b axis was oriented to the thickness direction and the a* and the c axis was oriented to the flow direction, was quite different from that of the transcrystal. This b-axis orientation results from the orientation of the plate plane of talc, which induces the nucleation and the crystallization under shear flow.