Effects of melt temperature and hold pressure on the tensile and fatigue properties of an injection molded talc-filled polypropylene

Abstract

This article examines the effects of melt temperature and hold pressure on the static tensile and fatigue behavior of an injection-molded 40 wt% talc-filled polypropylene. Injection molding caused anisotropy in the material. Both yield strength and fatigue strength were higher in the flow direction. The presence of weld line caused a large reduction in yield strength and fatigue strength. For specimens in the flow direction, both yield strength and fatigue strength increased with increasing hold pressure, but they were relatively insensitive to melt temperature. For specimens normal to the flow direction, both yield strength and fatigue strength increased with increasing hold pressure and decreased with increasing melt temperature. For specimens containing a weld line, the yield strength and fatigue strength increased with increasing hold pressure as well as increasing melt temperature. The observed differences in properties are explained in terms of the skin-core morphology, which was influenced by both melt temperature and hold pressure. POLYM. ENG. SCI., 45:755–763, 2005. © 2005 Society of Plastics Engineers