The influence of injection molding on tribological characteristics of ultra-high molecular weight polyethylene under dry sliding

Abstract

The objective of this study is to investigate the effects of various injection molding process parameters on the tribological properties of ultra-high molecular weight polyethylene (UHMWPE). The tribological properties, such as the friction coefficient and wear volume loss, were obtained using the Schwingum Reibung Verschleiss (SRV, oscillation friction wear) ball-on-plane wear tester. In addition, the mechanical properties of UHMWPE were investigated as well. The variable parameters of the injection molding process were melt temperature, mold temperature and injection velocity. Experimental results show that different wear contact loads and varied injection molding conditions influence the friction coefficient and wear volume loss of the UHMWPE specimens. As the sliding contact loads increased, the friction coefficient also increased. Moreover, the lowest wear volume loss mostly occurred in highest injection molding conditions. The morphologies of the worn surfaces and the specimen cross sections were examined with an optical microscope and a scanning electron microscope, respectively. Plastic deformations, grooves and wavelike formations are the main wear mechanism on the surface in the UHMWPE wear tests. Experimental results also showed that the tensile strength and surface hardness are affected by injection molding conditions and sliding contact loads.