Investigation of film–substrate interfacial characteristics of polymer parts fabricated via in-mold decoration and microcellular injection molding process

The appearance quality of foamed polymer parts can be improved by introducing high-appearance quality decorative films. However, the interfacial bonding characteristics of film that penetrated the surface of the substrate are few studied. In this paper, the foamed polypropylene (PP) parts with decoration films penetrated on the surface were prepared by the in-mold decoration and microcellular injection molding (IMD/MIM) process. The interfacial characteristics of the IMD/MIM parts were investigated experimentally through peeling tests and interfacial morphology. Based on the finite volume method, the coupled heat transfer model was established to calculate the temperature field in IMD/MIM process by taking into account the coupled heat transfer between polymer melt, film, and mold. The thermal response in the IMD/MIM process was numerically analyzed. The results show that the higher temperature on the polymer melt–film interface corresponds to relatively higher crystallinity and larger crystallite size and also favors the forming of the β-form crystal, which is beneficial to higher adhesion strength. The IMD/MIM parts can obtain a firm film–substrate adhesion and a uniformly strong bond between the film and the substrate.