CHAPTER 9 - Wear behavior of carbon nanotube-reinforced polyethylene and epoxy composites

Abstract

Abstract The effect of carbon nanotube (CNT) reinforcement on the sliding wear behavior of epoxy (EP) and ultra-high molecular weight polyethylene (UHMWPE) was studied under uniform sliding against martensitic bearing steel (100Cr6) and austenitic stainless steel (X5CrNi18-10) in a ball-on-prism arrangement. The epoxy-based composites were prepared in various ways to study the effect of the dispersion method on the tribological properties: purification/activation in concentrated nitric acid, treatment in a coupling agent, sonication and a variety of mixing devices were employed. The CNT content was varied systematically to find the optimal filler content. It was found that the wear rate and its scatter are minimal when the CNT content is approximately 1 wt%. The wear rate of this compound could be further reduced by adding dry lubricants. The best wear resistance was found for a compound containing 1% CNTs plus 10% graphite. The CNT-reinforced polyethylene composites were prepared by melt mixing in a kneader. Various amounts of CNTs were dispersed in a mixture of 80 wt% UHMWPE and 20 wt% high density polyethylene. The unreinforced PE matrix had already a relatively good wear resistance. CNT reinforcement could further improve the wear resistance, but only to a minor degree. The optimum filler content was again between 0.2 and 0.5 wt%. The type of counterpart material was found to affect the wear rate of the composite drastically. The wear rates of the compounds were several orders of magnitude lower against austenitic stainless steel than against the hard bearing steel.