βα-BIFURCATION OF GROWTH DURING THE SPHERULITIC CRYSTALLIZATION OF POLYPROPYLENE

Abstract

Spontaneous β to α polymorphic transition occurs from pinpoint nuclei on the periphery of the growing β-spherulite of polypropylene at a high crystallisation temperature (βα-bifurcation of growth), and its relative occurrence frequency increased with rising temperature. This is accompanied by a simultaneous decrease in growth rate. The phenomenon of βα-bifurcation of growth was interpreted through secondary βα-nucleation and the necessary energetic conditions and temperature dependence of this have been discussed.