The effects of gamma radiation sterilization and ageing on the structure and morphology of medical grade ultra high molecular weight polyethylene

Ultra high molecular weight polyethylene (UHMWPE) that had been sterilized with 25 kGy of gamma radiation and non-sterile material processed from the same batch were studied following five years of ageing in air. Differential scanning calorimetry, small angle X-ray scattering, transmission electron microscopy, Fourier transform infra-red spectroscopy and density gradient column measurements were used to characterize the changes in structure and morphology of the UHMWPE as a result of sterilization and shelf ageing. Significant changes were observed. The UHMWPE oxidized and increased in crystallinity as well as density, with chain scission the dominant response to irradiation. The applicability of the results of this study to the evolution of mechanical properties and structural integrity of medical grade UHMWPE for total joint replacement is addressed. Published by Elsevier Science Ltd.