ESCA analyses were performed on the frictional tracks on metal blocks covered with the transfer films of PTFE-based composites containing zinc, copper, and lead powders. Results show that the tribochemical reactions between PTFE and an aluminum or an iron counterface as well as between PTFE and zinc filler were found to occur under experimental conditions. Compounds of iron or aluminum fluoride were detected at the interface between the transfer film and the steel or aluminum substrate when PTFE composite pins rub against a steel or an aluminum counterface. This means that a chemical reaction between them has occurred. But the formation of a chemical bond between the transfer film of the composite and the substrate is not the real reason why metallic fillers reduce the wear of the PTFE, because the chemical reaction can also be detected when a pure PTFE pin rubs against a steel or an aluminum disk under these test conditions. The consumption of fluorine in PTFE at the interface between the films and the substrate is much more serious than that on the surface of the transfer films. It was found that the chemical reaction of the PTFE to the steel or aluminum substrate is by means of the fluorine atom and not the carbon atom in the PTFE.
