Investigation of HDPE wear debris formed by friction against metal surfaces with different oxide film content

Abstract The work presents the results of simulation of the local oxidation process of a metal surface and its influence on the chemical composition of wear products formed by polyethylene sliding against tungsten-cobalt hard alloy in an inert gas environment. Using IR spectroscopy, pyrolytic mass spectrometry, differential thermal analysis and electron paramagnetic resonance spectrometry, it was found that the chemical composition of low-molecular weight substances dissolved in the wear debris depends on the oxide content on the metal surface. Depending on the concentration of oxide, the wear debris accumulates different low-molecular weight products including water, carbon oxides, hydrocarbons, partial products of their oxidation and metal-containing substances. The wear rate of the polymer is characterized by a linear dependence on the relative area of oxide film. Its break is presumably connected with the optimum content of associated oxygen participating in polymer spatial cross-linking by carboxylation and ester bridge formation as well as the formation of metal-containing substances of oxyhydroxide, carbonate and organic metal salt type. The change in friction coefficient correlates with the yield of low-molecular weight hydrocarbons. The formation of a local metal oxide film has a significant influence on the parameters of the tribological system owing to excitation of tribochemical processes causing the generation of polymer oxidation products in the friction contact zone.