TRANSCRYSTALLIZED INTERPHASE IN THERMOPLASTIC COMPOSITES .1. INFLUENCE OF FIBER TYPE AND CRYSTALLIZATION TEMPERATURE

Hot-stage microscopy and differential scanning calorimetry were used to investigate the isothermal crystallization of polypropylene in the presence of a large variety of fibres. The occurrence of transcrystallization was found to depend on the type of fibre used and the crystallization temperature. The list of fibres which transcrystallize polypropylene is similar to that for other semicrystalline thermoplastics. In particular we found that aramid fibres and high-modulus carbon fibres do induce transcrystallization, whereas high-strength carbon fibres and glass fibres do not transcrystallize polypropylene. The radial growth rates of the polypropylene spherulites and the transcrystallization region were found to be identical over a range of isothermal crystallization temperatures. However, the ability of aramid fibres and high-modulus fibres to induce transcrystallization in polypropylene is dependent on the crystallization temperature. No transcrystallization was observed in quiescently crystallized polypropylene above 138-degrees-C.