CORRELATIONS FOR THE QUIESCENT CRYSTALLIZATION KINETICS OF ISOTACTIC POLYPROPYLENE AND POLY(ETHYLENE-TEREPHTHALATE)

The Nakamura equation is used to generate a direct relation (first-ord er differential equation) between the Avrami and Ozawa crystallization rate constants. As a result, it is possible to compare isothermal and constant-cooling-rate crystallization data in a consistent manner. Th is is done for isotactic polypropylene (i-PP) and poly(ethylene tereph thalate), based upon data available from the literature. Resulting cor relations are obtained for these two materials at atmospheric pressure as well as for i-PP at elevated pressure. The results corroborate tha t the maximum crystallization rate occurs approximately midway between the glass-transition and melting temperatures. In addition, the resul ts imply that there is no need to explicitly incorporate an induction time when the modelling is based upon the Nakamura equation.