Nano- and Micro-Structured UHMWPE Composites Filled With Hydroxyapatite Irradiated by Nitrogen Ion Beams for Bio-Medical Applications

The effect of filling the ultra-high-molecular-weight polyethylene (UHMWPE) with nano- and microparticles of hydroxyapatite (HA) on its structure and tribotechnical properties is investigated, aiming at application of the modified UHMWPE in endoprosthetics. An introduction of 0.1-0.5 wt% HA nanoparticles into UHMWPE is shown to result in a threefold increase in its wear resistance. A similar effect is observed in the case where 20 wt% of HA microparticles is used. Treatment of the surface of nano- and microcomposites with a nitrogen ion beam increases the wear resistance by an additional 10-30%. A combined treatment of UHMWPE powder and fillers in a planetary ball mill leads to a uniform distribution of the latter in the polymer matrix and, consequently, to the formation of a more ordered permolecular structure. In the irradiated UHMWPE micro- and nanocomposites reinforced with HA, the tribotechnical properties are shown to improve due to the formation of new chemical bonds (primarily via cross-linking) and ordered permolecular structure.