Micromorphologic feature of the crystallization of isotactic polypropylene after melt-shearing

Abstract

The formation of β-cylindritic micromorphologic structure produced by pulling a Kevlar fiber from an isothermal crystallizing β-nucleated isotactic polypropylene melt (at Tc=133°C) has been studied by using polarized light microscope, phase contrast optical microscope, scanning electron and atomic force microscopes. The micrographs reveal a clearly interfacial shear zone, α-cylindrite, β-cylindrite and β-spherulites near the sheared layer. Some of the point-like β-nuclei was not originated from the surface of the interfacial shear zone. A modified model based upon the theory of shear-induced crystallization can explain the phenomenon of polymorphic structure and the boundary shape near the interface without assuming epitaxial growth.