THE EFFECTS OF HYDROGEN-PEROXIDE AND STERILIZATION ON THE STRUCTURE OF ULTRA-HIGH-MOLECULAR-WEIGHT POLYETHYLENE

The effects of hydrogen peroxide and sterilization on the structure an d morphology of medical-grade ultra high molecular weight polyethylene (UHMWPE) were studied. Microstructural changes were induced via gamma irradiation sterilization and were accelerated by aging in hydrogen p eroxide. Differential scanning calorimetry, density gradient column, t ransmission electron microscopy and small-angle X-ray scattering were used to characterize the structure. Upon oxidation, a decrease in melt ing temperature, an increase in heat of fusion, an increase in density , a tortuosity in lamellae, and a tendency to microcrack were observed . Based on the results, a mechanism for the oxidation of UHMWPE is pro posed in which oxygen is incorporated into the amorphous phase of the polymer, leading to the development of strains and the breaking of tie molecules in the polymer, which result in the microcracking and embri ttlement of the material. (C) 1998 Elsevier Science Limited. All right s reserved.