Effect of Viscosity Ratio on the Crystalline Morphologies and Mechanical Property of Multi-Melt Multi-Injection Molded Parts

The effect of viscosity ratio (ηcore/ηskin) on the crystalline morphologies of the bars molded by multi-melt multi-injection molding (MMMIM) was investigated by fixing a kind of high density polyethylene (HDPE) with a high molecular weight as the skin material and tuning the viscosity ratio by the viscosities of different core melts. The hierarchical morphologies and mechanical properties were investigated by PLM, SEM, 2D-WAXS and tensile testing. It was found that higher viscosity ratio facilitated the interaction between the skin and core melts ascribed to greater chain entanglement, and induced a higher degree of molecular orientation accompanied by improved mechanical properties.