Asymmetric Cooling Dynamics in Foamed <scp>PP</scp> : Role of Metal/Polymer Films on Formability

ABSTRACT Microcellular injection molding (MIM) is hindered by surface quality issues caused by bubble defects, which severely limit its industrial application. This study innovatively combines in‐mold decoration (IMD) with MIM, using copper foil (Cu) and polyethyleneterephthalate films to regulate the interface heat transfer and cell evolution. By integrating numerical simulations with experiments, the study reveals the asymmetric regulation mechanism of heat transfer paths by the film materials and explores the impact of the film material on the surface quality, cell structure, and mechanical properties of the molded parts. The experimental results indicate that IMD effectively improves the surface quality of microcellular molded parts, enhances surface hydrophilicity, and promotes surface crystallization. The copper foil accelerates cooling on the film side, reducing cell size and increasing cell density, while the core layer's cell structure shifts toward the nonfilm side. The PET film, with lower thermal conductivity, causes an increase in cell size, and the core layer's cell structure shifts toward the film side. Molded parts incorporating IMD exhibit markedly superior mechanical performance, with tensile, flexural, and impact strengths increased by 31.7%, 41.8%, and 32.8%, respectively, compared with nonfilm counterparts. This study provides scientific evidence and practical guidance for further optimizing the MIM process and part performance, contributing to the advancement of MIM technology for high‐strength, high‐appearance, and low‐density materials.