Friction And Wear Properties Of Filler-modified Uhmwpe

Ultra-high molecular weight polyethylene (UHMWPE) has been widely used as a bearing material in total joint replacement components for over 35 years. Although UHMWPE has many properties making it an excellent choice for this application, wear is the primary cause of failure in joint replacement prostheses. In this study, UHMWPE was modified with filling of nano ZrO₂, nano SiO₂ and micron PTFE powders. The effects of the filled powders on the tribological properties of UHMWPE were investigated.The pure UHMWPE and a series of UHMWPE composites reinforced by different kinds of powders were prepared by heat moulding. The structure changes of UHMWPE with the filling of powders were studied by IR test. The hardness and wetting angle of treated and untreated UHMWPE were measured, and it would be the reference of the research on the tribological properties of UHMWPE composites. The tribological properties were investigated under three different lubricating conditions including distilled water, saline and serum by sliding against CoCrMo alloy and Si₃N₄ ceramic ring. The effects of filling amount, particle size, kind of powder and the counterface material on the tribological properties of UHMWPE composites were studied. The morphologies of the worn surfaces were observed with optical microscope to analyze the tribological behavior and wear mechanism of UHMWPE composites synthetically.As a result, the hardness and wetting ability of UHMWPE were all improved with proper filling amount. The results of friction and wear tests showed that the wear resistance of UHMWPE was improved after filling with the powders. When different sizes of nano powders were filled in, UHMWPE composite which filled with bigger size nano powder exhibited better tribological properties. The surface treatment of nano powder had little effect on the tribological properties of UHMWPE composites, and the composite filling with less powder which had been surface treated had a better wear resistance. When sliding against CoCrMo alloy ring, the composite which filled with 2% nano ZrO₂-02 showed the best tribological properties. And when sliding against Si₃N₄ ceramic ring, the composite that filled in 3% nano SiO₂-03 exhibited the best tribological properties.