Injection molding of semicrystalline polymers. II. Modeling and experiments

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Abstract
The injection molding of an isotactic polypropylene was computer‐simulated with both quiescent and shear‐induced crystallization taken into account. A one‐dimensional finite difference model was used to simulate the filling, packing, and cooling stages of the injection‐molding cycle. The Spencer‐Gilmore equation was used to relate the density variations to the pressure and temperature traces in the packing simulation. The quiescent crystallization kinetics was modeled by the differential form of the Nakamura equation. The theory developed by Janeschitz‐Kriegl and co‐workers was used to model the shear‐induced crystallization kinetics. The pressure traces during the filling and packing stages of the molding cycle, the thickness of the shear‐induced crystallization layer, and the crystallinity profile throughout the thickness of the part were measured and compared with predicted values. © 1995 John Wiley & Sons, Inc.