INVESTIGATION OF ADHESION WEAR OF FILLED POLYTETRAFLUOROETHYLENE BY ESCA, AES AND XRD

In this paper more than 15 polytetrafluoroethylene (PTFE)-based composites incorporated by metal powders or metal oxides were studied by rubbing against smooth surfaces of steel, aluminium and copper on a reciprocating tester. Experiments based on sliding a pure PTFE pin against different metal blocks showed that the wear rate of pure PTFE does not change with the chemical properties of the counterface. Similar results have been obtained when pins of composite or pure PTFE are alternately rubbed against the same track of the block. The experimental results show that wear rate of PTFE-based composites filled by metal powders or metal oxides are lower than the wear rate of pure PTFE by a factor of about 1000 and the frictional properties of these composites are nearly the same as those of pure PTFE. The wear behaviour of pure PTFE was not affected by chemical activity of the counterface and a layer of transfer film of PTFE-based composites preferentially transferred onto the frictional track. X-ray diffraction (XRD) analysis showed that these metal powders disrupt the banded structure of PTFE and decrease its wear rate. Electron spectroscopy for chemical analysis of the frictional tracks on the metallic blocks suggested that chemical reaction of PTFE with zinc in the PTFE-based composite filled with zinc occurred under the experimental conditions. This reaction between PTFE and zinc was found to promote the preferential transfer of zinc from the composite to the counterface, resulting in a great reduction in the wear rate of the composite. Auger electron spectroscopy (AES) and its depth profiling analyses across the tracks on the blocks showed that a transferred film of pure PTFE may be formed on top of the transferred layer of PTFE-based composites on the metallic blocks but the transferred layer of the composites does not reduce the wear rate of pure PTFE. © 1990.