CRYSTALLIZATION OF FIBER-REINFORCED POLY(PHENYLENE SULFIDE) COMPOSITES .2. MODELING THE CRYSTALLIZATION KINETICS

The kinetic data obtained by differential scanning calorimetry for the isothermal crystallization from the melt of unreinforced poly(phenylene sulfide) (PPS) and of model carbon, aramid, and glass fiber-reinforced PPS composites has been analyzed and modeled on the basis of the Avrami equation. The classical Avrami model provided a good description of the volume fraction crystallized for PPS and for those composities that did not exhibit transcrystallinity in thin-film specimens. Nonlinear Avrami behavior was observed for those composite systems that did exhibit transcrystallinity, for which parallel and series dual Avrami models were used. A series crystallinity model, which corrects the volume fraction crystallized for structural imperfections, was applied to all the systems, providing a reasonable modeling of the data. In this model, we postulate an initial primary crystallization followed by a secondary crystallization. The temperature dependencies of the Avrami rate constants were analyzed through Arrhenius relationships, and the resultant activation energies and frequency factors were interpreted in terms of nucleation and growth phenomena. We found the frequency factor for primary crystallization to be indicative of the nucleating abilities of the fiber surfaces and to correlate with the presence of transcrystallinity.