An Investigation into Bond Strength of Injection Overmolded Polypropylene

Abstract

The aim of this research was to investigate the influence of injection overmolding parameters on the bond strength between substrate and overmolded polypropylene. The injection overmolded temperature, substrate temperature, and holding pressure on the tensile and impact strengths of injection overmolded part were studied in details. In addition, the effects of contact distance and surface pattern on the lap shear strength were also main interest. The experimental results indicated that the bond strength particularly increased with increasing substrate temperature, while less significant effect was found with increasing overmolded temperature. It can be seen that the shear strength tended to decrease with the increase of contact distance. This was associated with the decrease of intermolecular diffusion at the interface as increase in flow distance. Furthermore, the significant improvement of shear strength was found by using the perpendicular and parallel groove patterns on the substrate surface.