Crystallization studies on heterogeneous melts of polybutene-1

Abstract

The heterogeneous melts of isotactic polybutene-1 (iPB-1) containing Form I or Form II seeds with uniform size and random distribution were prepared by selective melting of melt crystallized and transformed samples, respectively. Compared with a reference blank melt, the remnant Form I or II seeds are able to significantly reduce the half-time of crystallization under isothermal conditions. Besides, the nucleation efficiency of Form II seeds is much higher than that of Form I seeds because of the lower lateral surface energy and highly lattice match. Furthermore, a great number of tiny spherulites with submicrometer radius nucleate and grow simultaneously, offers an opportunity to follow the development of spherulites at the very early stage. The analysis of the differential scanning calorimetry (DSC) curves confirms that the mass fraction for faster primary crystallization of heterogeneous melts is lower than that of blank melt, which clearly indicates that growth rate of spherulites is decreasing before impingement. The radius of spherulites was not much larger than the diffusion length provides the foundation for the observed non-linear growth of spherulites. This quantitative comparison of the crystallization kinetics of blank melt and heterogeneous melts can therefore be applied as a method to improve our understanding of nucleation and the diffusion-controlled growth of polymer.