The Effect of Crosslinks on the Sliding Wear of High-Density Polyethylene

Abstract

The purpose of this study was to determinate the influence of the molecular crosslinking in the wear resistance of a linear polyethylene (PE) sliding against a rough steel surface. A set of PEs with different degrees of crosslinks were obtained by chemical modification of a PE with varying concentrations of organic peroxide. The amount of gel, molecular weight between crosslinks (Mc), crystallinity and Vickers microhardness were determined in the crosslinked PE’s. The tribological performance of the materials was evaluated under dry sliding conditions using a block-on-ring tester. The coefficient of friction and the wear rate were determined in experiments in which a sample of polymer was contacted with the peripheral surface of a steel ring rotating at constant velocity. The wear resistance of the crosslinked materials increases with the amount of gel and when Mc decreases. The crosslinked PE showed a wear rate lower than the original PE when the amount of gel was larger than 80 % of the total mass. The coefficient of friction of the PE and crosslinked material was about 0.2 regardless of the normal load applied. The analysis of the worn surfaces by optical and SEM microscopy reveals that the primary mechanism involved in wear is abrasive wear.