Modelling Post-molding Warping

Abstract

Abstract The post-molding warping of injection molded parts is strongly influenced by thermal expansion history. We show that a thermal expansion hysteresis loop occurs, so that heating and cooling curves can sometimes be different, due to microstructural changes. Following an extensive investigation of thermal expansion for a polypropylene, we propose a model to predict the specific volume change during post thermal treatments. The model predictions are in good agreement with the experimental measurements.