Composite lubricating layer with enhanced wear-resistant properties between HXLPE and Cu/ZrO2 ceramic friction interface

Poly (2-methacryloyloxyethyl phosphorylcholine) (PMPC), as a highly hydrophilic as well as biocompatible material, has been widely used in biomedical applications. In this study, the friction reduction and wear resistance of HXLPE were improved by grafting PMPC on its surface. However, the PMPC will be sheared off during friction, which is difficult to meet the long-term service requirements of artificial joints. This can be achieved by improving the lubrication environment to minimize PMPC shedding. To simulate the human lubrication environment, free PMPC (lubrication factor) and Cu 2+ (transition group metal ion catalyst) were added to neonatal bovine serum (NBCS). When the friction pair consisting of grafted PMPC-modified HXLPE and Cu/ZrO 2 ceramics is rubbed therein, the grafted PMPC interacts with the free PMPC, while Cu 2+ catalyzes the oxidative hydrolysis of serum proteins into carbon-containing small molecules and adsorbs on the surface of the Cu/ZrO 2 ceramics to form a carbon-rich lubrication layer. The composite lubrication layer consisting of grafted-free PMPC and carbon-rich lubrication layer provides good load-bearing and lubrication properties at the friction interface. And the wear rate is reduced by 45% compared to rubbing in deionized water. This technique can reduce the shedding of grafted PMPC state and improve the load-bearing performance of the interfacial lubrication layer, thus reducing the wear of HXLPE and prolonging the service life of the artificial joint.