UHMWPE Modified by Halogenating Reagents: Study on the Improvement of Hydrophilicity and Tribological Properties

Three groups of ultra-high-molecular-weight polyethylene (UHMWPE) with optimum hydrophilicity were obtained by halogenation modification. They were immersed in a 15% KBr solution for 30 h, a 10% NH4Cl solution for 60 h, or a 15% NH4Cl solution for 60 h. The mechanism of hydrophilicity enhancement by halogenation modification was investigated by combining surface morphologies and energy spectrum analysis. Friction and wear tests were carried out to measure the friction coefficients of modified UHMWPE under different test conditions, and the wear volume and morphologies of the worn surfaces were studied to explore the friction and wear mechanism. The results showed that the best tribological properties were obtained when immersed in the 15% KBr solution for 30 h. Furthermore, the synergistic optimization effect of hydrophilicity enhancement on tribological properties was explained by the lubrication mechanism, as well as the influence of interfacial properties change on the wear mechanism. This study provides an experimental and theoretical basis for using halogenated UHMWPE.