Improved wear and mechanical properties of UHMWPE–carbon nanofiber composites through an optimized paraffin-assisted melt-mixing process

There is a huge demand for improving the properties of ultra-high molecular weight polyethylene (UHMWPE), especially in biomedical applications where joint replacement recipients frequently suffer from premature degradation of the joint integrity. Composite technology is generally a viable option for improving these properties in many analogous applications. However, UHMWPE is extremely viscous, and processing of bulk composites is normally limited to dry-mixing before compression molding, which yields very poor and unpredictable distribution of fillers. In this study, carbon nanofiber (CNF)–UHMWPE composites were prepared by melt-mixing assisted by swelling with paraffin oil. The paraffin-assisted melt-mixing resulted in much improved distribution and dispersion of fillers at low loadings when compared to conventional processing methods of bulk UHMWPE; however the dispersion at higher loadings was initially unsatisfactory. Subsequently the paraffin oil concentration was optimized and the yield of the final UHMWPE composite was improved. Wear testing at the low loading of 1 wt.% resulted in an optimal amount of paraffin and further enhanced wear properties at 35 vol.% UHWMPE to paraffin, a final composite yield much higher than that found in the literature using similar processing techniques.