Two-level Wear Reduction Mechanism and Molecular Dynamics Simulation for GR/PTFE Composites

To study the mechanisms of wear of graphene oxide-polytetrafluoroethylene (GR/PTFE) composites, the effects of surface mechanical properties and molecular interactions on the wear behaviour of composite are investigated by using environmental wear tests, nanoindentations, and adhesion force measurements. The mechanism of wear of composite is further studied by using molecular dynamics simulation for the frictional interface. Experimental results showed that the use of graphene filler reduces the wear of PTFE by 99.8% in the atmospheric environment. In dry argon, the wear rate of the composites is an order of magnitude higher than that in atmospheric environment. Nanoindentation tests suggested that the surface hardness, elastic modulus and adhesion force of the composite after wear in atmospheric environment are 43.4%, 47.4% and 68.5% higher than those of the worn surface in dry argon environment, respectively. The measurements of water contact angle and infrared spectroscopy showed that the composite surface after wear in atmospheric environment has stronger polar interaction than the original surface. Molecular dynamics simulations suggested that stronger polar interactions improved the mechanical properties of the composites and the adsorption of transfer films, and they synergistically reduce the wear of the composites.