Numerical simulation on crystallization-induced warpage of injection-molded PP/EPDM part

Prediction on crystallization-induced warpage in injection-molded semi-crystalline polymers is important in satisfying the required specifications of molded products. In this study, we chose a polypropylene (PP)/ethylene propylene diene monomer (EPDM) blend as the model system, and use Autodesk’s Moldflow Insight to simulate the crystallization behavior and the influence on the warpage of the injection-molded box-shaped PP/EPDM sample. The required crystallization parameters of the PP/EPDM were taken from differential scanning calorimetry (DSC) and experimentally estimated on a similar PP in the Moldflow material library. The FWO, Jeziorny, and Coats-Redfern methods were applied to describe the crystallization kinetics and estimate the required crystallization parameters. The simulation on warpage was then conducted with and without the crystallization. When the crystallization is considered, the warpage of the box-shaped PP/EPDM increased more significantly than that for the PP, which can be attributed to the more uneven crystallization resulting from slower crystallization kinetics of the PP/EPDM. With a 10 °C increase in the coolant temperature, which reduced temperature gradient in the sample, a spatially more homogeneous crystallization can be achieved. Consequently, the side edge warpage of the injection-molded box-shaped PP/EPDM decreased considerably.