Wear and Friction Reduction on Polyethersulfone Matrix Composites Containing Polytetrafluoroethylene Coated with ZrW2O8 Particles at Elevated Temperatures

Polymer matrix composites (PMCs) have been prepared having a polyethersulfone (PES) matrix loaded with polytetrafluoroethylene (PTFE) particles coated with negative thermal expansion zirconium tungstate (ZT) with an aim to reduce the thermal mismatch stresses at the PES/PTFE interfaces and, thus, reduce wear rate when sliding against a ball bearing AISI 52100 steel counterpart at elevated temperatures. The zirconium tungsten particles were synthesized using thermal decomposition from hydrothermally prepared precursors. The PMCs have been obtained using compression molding at 370 °C and contained, according to XRD, only the hexagonal α-ZrW2O8 phase. Wear testing was carried out at 25, 120, and 180 °C using a ball-on-disk scheme at 5 N and 0.3 m/s. The resulting wear tracks’ radial profiles were registered by means of profilometry, which was then used for calculating the wear rate. It was shown that both wear rate and friction reduced in testing the PES/PTFE/ZT samples at 180 °C compared to those of PES/PTFE containing only neat PTFE particles. Wear mechanism transitions have been observed from low-temperature generation of the tribological layer by the PTFE smearing to flow and abrasion wear at high temperatures.