The effects of peroxide content on the wear behavior, microstructure and mechanical properties of peroxide crosslinked ultra-high molecular weight polyethylene used in total hip replacement.

The wear of the ultra-high molecular weight polyethylene (UHMWPE) acetabular components and wear debris induced osteolysis are the major causes of failure in total hip replacements. Crosslinking has been shown to improve the wear resistance of UHMWPE by producing a network structure, resisting the plastic deformation of the surface layer. In this study organic peroxides were used to crosslink two different types of UHMWPE resins, using hot isostatic pressing as the processing method. The effects of peroxide content on the different properties were investigated, along with the effect of the crosslink density on the wear behavior. An increase in peroxide content decreases the melting point and the degree of crystallinity, which results in a decrease in the yield strength. The ultimate tensile strength remains essentially unchanged. The molecular weight between crosslinks decreases with an increase in the peroxide content and reaches a saturation limit at around 0.3-0.5 weight percent peroxide, its value at the saturation limit is a function of the virgin resin used for processing. The wear rate decreases linearly with the increase in crosslink density.