Optical Microscopic Study on the Morphologies of Isotactic Polypropylene Induced by Its Homogeneity Fibers

Abstract

Through introducing the iPP fibers into their supercooled homogeneity matrices, the homogeneity fiber/matrix composites of iPP have been prepared, and the resulting supermolecular structures of iPP matrices induced by their homogeneity fibers as a function of introduction temperature were studied by means of optical microscopy. The results show that the supermolecular structures of iPP matrices induced by their homogeneity fibers can be ascribed to the transcrystallization of iPP triggered by strong heterogeneous nucleation rather than the shear stress produced by fiber introduction. The morphological features demonstrate that the interfacial transcrystalline iPP is composed of purely α-form if the fibers were introduced at 138 °C. With increase of fiber introduction temperature, an increasing content of β-iPP surrounding the iPP fibers has been observed. A transcrystallization layer of mainly β-modification iPP can be obtained when the fiber introduction temperature was set at 173 °C. This is associated with melting or at least partial melting of the iPP fibers. The formation of rich α-iPP transcrystallization layers at an even higher fiber introduction temperature, e.g., 178 °C, further demonstrates that the melting state of the iPP fibers plays an important role in generating the β-iPP.