THE EFFECTS OF GAMMA-RADIATION STERILIZATION AND AGING ON THE STRUCTURE AND MORPHOLOGY OF MEDICAL GRADE ULTRA-HIGH-MOLECULAR-WEIGHT POLYETHYLENE

Ultra high molecular weight polyethylene (UHMWPE) that had been steril ized with 25 kGy of gamma radiation and non-sterile material processed from the same batch were studied following five years of ageing in ai r. Differential scanning calorimetry, small angle X-ray scattering, tr ansmission electron microscopy, Fourier transform infra-red spectrosco py and density gradient column measurements were used to characterize the changes in structure and morphology of the UHMWPE as a result of s terilization and shelf ageing. Significant changes were observed. The UHMWPE oxidized and increased in crystallinity as well as density, wit h chain scission the dominant response to irradiation. The applicabili ty of the results of this study to the evolution of mechanical propert ies and structural integrity of medical grade UHMWPE for total joint r eplacement is addressed. Published by Elsevier Science Ltd.