Influence of adding graft UHMWPE and nanofillers onto wear resistance of Ultra-High Molecular Weight Polyethylene (UHMWPE) mixture

UHMWPE (Ultra High Molecular Weight Polyethylene) is widely used in the medical application and is a promising structural material for application in mining, chemical, mechanical engineering. Having very low friction coefficient it might be used even instead of metal friction parts but it calls for further increase of its physical mechanical properties. It is one of the very high resistant materials but it is difficult to bond with other substances. One of perspective ways to bond UHMW-PE with filler is its grafting. There is one more interesting approach, when graft UHMWPE is added to UHMW-PE in order to react both with latter and nanofiller. This might be achieved be adding different kind of fillers, in particular nanoscale ones. In this paper we attempted to increase the mixture ability of UHMWE-graft-SMA with Cu, CNF and Al₂O₃ for enhancing its wear resistance properties and study the changing of hardness after mixing. We employed UHMWPE powder and graft UHMWPE with anhydride and carboxyl functional groups realized by modification of the polymers in reacting gases (UHMWPE-g-SMA). It was assumed that grafting will provide adhesion between UHMWPE particles. UHMWPE-g-SMA and UHMWPE were mixed using a high speed homogenizer in dry form. The mixture was pure UHMWPE with 0, 3, 5, 10 and 20 wt% of UHMWPE-g-SMA. This material is denoted as UHMWPE-g 0, 3, 5, 10, 20 respectively. And then add 0.5% CNF (Carbon Nano Fiber), 0.5% Cu (nanosize) and 0.5% Al₂O₃ (nanosize) to their mixture. The wear resistance of UHMWPE + UHMWPE-g-SMA specimens is increased when UHMWPE-g-SMA is mixed with UHMWPE powder and nanofillers. Cu, CNF and Al₂O₃ nano filler were added to UHMWPE the wear intensity is rather different from UHMWPE in initial state (pure) and give rise to increase wear resistance. The results of the wear tests have shown that the highest wear resistances of each group of fillers are UHMWPE-g 3 with 0.5% Cu, U- MWPE-g 3 with 0.5% CNF and UHMWPE-g 10 with 0.5% Al₂O₃. However, in contrast with this result, wear resistances is increased when UHMWPE-g-SMA and nanofillers were added. In case of hardness property, hardness does not change effectively.