A novel approach to the study of extensional flow-induced crystallization

Abstract

A systematic experimental investigation of the coupling between the extensional flow and the crystallization of a commercial grade polypropylene is presented. A modified Sentmanat extensional device allows one to generate a uniaxial extensional flow in the absence of gravity sagging and monitoring its effect on the kinetics of crystallization via in-situ visualization of the sample in polarised light. As compared to the shear induced crystallization, a three fold increase of the kinetics of the extension induced crystallization is found. The study is complemented by a post mortem analysis of the crystalline morphology by small angle X ray scattering (SAXS) and wide angle X ray scattering (WAXS).