A Scanning Electron Microscopy Study on the Morphologies of Isotactic Polypropylene Induced by Its Own Fibers

Abstract

The morphologies of iPP fiber/matrix homogeneity composites were studied on a lamellar level with the help of a field emission scanning electron microscope. It is found that the induced supermolecular structure of iPP depends strongly upon the fiber introduction temperature. At temperatures lower than 164 °C, no melting of the original iPP fiber takes place, and the solid iPP fiber can initiate only the growth of parallel aligned α-iPP lamellae normal to the fiber axis. At temperatures above 165 °C, the morphological change from the microfibrils to lamellae implies the occurrence of melting and recrystallization of the iPP fiber during sample preparation. At the same time, the increment of β-iPP content with the increase of fiber introduction temperature demonstrates unambiguously that the β-iPP crystallization is associated with the above-mentioned melting and recrystallization process. Combining the structural features of the recrystallized iPP fibers and the induced interfacial layers, it is suggested that the chain orientation status in the molten iPP fiber plays an important role in subsequent β-iPP crystallization.