Flow‐induced crystallization during isotactic polypropylene film casting

Abstract

Abstract In this work, a previously proposed model for flow‐induced crystallization of polymers was slightly modified and successfully applied in describing film casting experiments performed working with isotactic polypropylene. In this process, the melt experiences flowing conditions, during the cooling. The effect of flow on crystallization kinetics was accounted for by the entropic increase of melting point because of the orientation effect of the flow. The orientation of the macromolecules was described by means of a nonlinear dumbbell model, and the entropic shift was calculated on the basis of the rubber elasticity theory. The flow‐induced crystallization model, using reasonable values for relaxation time, was proved able to quantitatively predict the enhancement effect of the flow as an increase of spherulite nuclei density and growth rate, in presence of low‐level flows (Deborah number <1–10). The morphology changes due to higher level of flow (fine grained, fibrils, shish‐kebab) were not predicted by this approach. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers