The effect of zinc and copper oxides and other zinc compounds as fillers on the tribological behavior of thermosetting polyester

The tribological behavior of thermosetting polyester filled with CuO, ZnO, ZnF2, and Zn(C18H35O2)2 fillers was studied. Sliding was performed in ambient atmosphere at 1.0 m s−1 between a polyester pin and a hardened tool steel disk in a pin-on-disk machine. The worn and the unworn specimen pin surfaces, zinc stearate powder, and the transfer films formed during sliding were studied by X-ray photoelectron spectroscopy (XPS). It was found that the coefficients of friction of all the filled composites were higher than that of the unfilled polyester. As for wear, the wear rate of polyester filled with ZnO and ZnF2 increased while that of polyester filled with CuO and Zn (C18H35O2)2 decreased. The reasons for these kinds of behavior were investigated. XPS results revealed that the Zn(C18H35O2)2 filler decomposed during the sliding process while ZnO did not. It has been hypothesized that decomposition of the filler helps in bonding of the transfer film to the counterface. The observed behavior is explained in terms of the topographical features, morphology and bonding of the transfer film to its counterface.