Influence of crystallization temperature on the morphologies of isotactic polypropylene single-polymer composite

The supermolecular structures of iPP fiber/matrix composites as a function of crystallization temperature were studied by means of optical microscopy. The results show that, even though partial melting of the iPP fibers is in favor of initiating the β-iPP crystal growth, the interfacial morphology of iPP single-polymer composites induced by its own fiber depends strongly on the crystallization temperature. It was found that transcrystalline structures of negative radial β_III-iPP or banded β_IV-iPP can be produced within the crystallization temperature range 105-137 °C, while transcrystallization zone of pure negative radial α_II-iPP crystals is observed at higher crystallization temperature, e.g. 141 °C. On the other hand, the surrounding iPP spherulites grown from the bulk are composed of α-iPP in the whole crystallization temperature range. However, the optical character of the spherulites is controlled by the thermal condition.