The friction and wear characteristics of nanometer ZnO filled polytetrafluoroethylene

The friction and wear characteristics of nanometer ZnO filled polytetrafluoroethylene (PTFE) composite blocks with different filler proportions in sliding against stainless steel ring under dry friction condition were studied. The microstructures, worn surfaces and transfer films of PTFE and nanometer ZnO/PTFE composite were then examined with scanning electron microscope (SEM). Experimental results show that filling nanometer ZnO to PTFE could greatly reduce the wear of this polymer and the best anti-wear property was obtained with the composite containing 15 vol.% nanometer ZnO. In comparison with pure PTFE, the friction property of these composites was maintained. With the increase of load and sliding velocity, the coefficient of friction of nanometer ZnO/PTFE composites was reduced and the anti-wear ability of them was not very damaged. It was seen from the cross-section micrographs of PTFE and nanometer ZnO/PTFE composite that the fiber structures that existed in pure PTFE were disappeared by filling nanometer ZnO into PTFE. This indicated that this filler could prevent the destruction of PTFE banded structures during friction process. SEM pictures of the transfer films indicated that with the frictional couple of stainless steel ring/composite block filled with 15 vol.% nanometer ZnO, a uniform and tenacious transfer film was formed on the ring surface, which promised an excellent anti-wear property of this composite. SEM examination of 15 vol.% nanometer ZnO/PTFE composite also showed that some cracks on the worn surface of the composite appeared during sliding under 300 N. The creation and development of the cracks led to deterioration of the wear property of this composite under higher load.