Prediction of Heat Conduction with Phase-change Effects during Cooling Stage of Injection Molding of High-density Polyethylene: Approximate Integral Approach

Phase-change problems, also known as the “Stefan problems” or “moving-boundary problems,” are practically significant in modern technological and engineering fields. Injection molding, one of the most widely used polymer processing techniques, can be divided into three stages: filling, packing, and cooling. The cooling stage, which accounts for over three fourths of total molding cycles, greatly affects both productivity and quality of the molded articles. In this work, an approximate integral method was adopted to predict the transient heat conduction with phase-change effects during the cooling stage of injection molding of crystalline polymers. Experiments were conducted to compare with the calculated results, and reasonable agreement was obtained. It was concluded that the present modeling makes good predictions for the cooling stage of injection molding of crystalline polymers, which may be applicable to further studies on the microstructure evolutions during injection molding process as well as the optimal designs in industrial applications.