Improvement of the Wear Resistance of Ultra High Molecular Weight Polyethylene (UHMWPE) by Radiation Crosslinking

摘要

The effect of thermal treatment and irradiation on the physico-chemical properties of ultra-high molecular weight polyethylene (UHMWPE) used in orthopedic implants was investigated. If a large amount of polymer radicals remain trapped after the irradiation of ultra-high molecular weight polyethylene (UHMWPE), the radicals may result in a significant alteration of its physical properties during shelf storage and implantation for a long time period. An electron spin resonance spectroscopic study was undertaken to investigate the remaining free radicals in UHMWPE after irradiation in air and a N_2 environment. Heat treatment was employed for various periods of time to scavenge the free radicals. The heat treatment of irradiated UHMWPE could substantially reduce the concentration of the free radicals; therefore the long-term oxidative degradation of UHMWPE was reduced. The surface oxidation on the UHMWPE samples according to irradiation and the thermal treating condition was verified by FTIR-ATR and electron spectroscopy for chemical analysis (ESCA). The polymer pin on metal plate type testing apparatus was used to test wear property. UHMWPE irradiated in the molten state had a higher crosslinking extent and a lower wear rate than one irradiated in the room temperature.