Prediction of Flow-induced Crystallization in Injection Molding
Peter Kennedy, Rong Zheng
Moldflow Pty Ltd
Australia

Keywords: Injection moulding, flow-induced crystalline, polypropylene

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We present a numerical simulation of flow-induced crystallization (FIC) in injection molding of an isotactic polypropylene. A FENE-P dumbbell model and a rigid dumbbell model have been used to describe the molecular chain conformation and the orientation evolution for the amorphous phase and the semi-crystalline phase, respectively. The effect of flow on crystallization is considered by relating excess free energy and flow-induced orientation to crystallization kinetics. Crystallization is coupled to the rheology of the material and influences the solidification. We predict a pronounced effect of short-term shear treatments in accelerating nucleation and flow-induced changes in morphological structures in the injection moulded part in terms of orientation, nuclei number, crystal growth geometry, size distribution of the spherulites, and skin-core structures.