The tribological behaviors of copper-coated graphite filled PTFE composites

Polytetrafluoroethylene (PTFE) composites filled with different fillers and various filler proportions were made by compression molding. The powders of graphite, copper, copper-coated graphite (CCG), and copper-mixed graphite (CMG) were selected as the fillers. The tribological behaviors of composites in sliding a stainless steel ring were evaluated on an MM-200 friction and wear tester. The morphologies and element chemical states of the worn composite surfaces were examined with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. It was found that the CCG particles prepared by chemical replacement method were characterized by loose and uniform covering of graphite particles by many tiny copper particles. The preferential transfer of graphite onto the surfaces of PTFE powders during the mixing process could be prevented by copper coating method, which was beneficial to further improving the wear resistance of composites. XPS analysis showed that no tribological reaction occurred during the friction process of PTFE sliding against stainless steel ring, but there was radical -CF₃ on the worn surfaces of PTFE composites, its generation mechanism and effect on the tribological behaviors of PTFE composites still need further study. (C) 2000 Elsevier Science S.A. All rights reserved.