Lubricating performance of polytetrafluoroethylene hybrid fabric composites with removed thermosetting resin at cryogenic temperatures

Abstract

AbstractAt cryogenic temperatures, the higher friction coefficient of conventional fabric composites severely inhibits the application of hybrid polytetrafluoroethylene (PTFE)/amide fabric composites in pivotal tribological pairs such as plain bearings operated at low temperatures. In order to improve the lubricating properties of fabric composites at cryogenic and wide temperature ranges, a novel hybrid PTFE/Nomex fabric composite is prepared by peeling off the facial phenolic formaldehyde resin through the Hot‐Press Mechanical Stripping method, which is named Phenolic Formaldehyde Mechanical Stripping (PFMS). The friction coefficient of PFMS is 0.06 at 296 K, and can be as low as 0.1 at 123 K, reduced by up to 58% compared to conventional fabric composite without resin removal. Furthermore, the friction coefficient of PFMS first increases and then decreases as the temperature decreases, the turning point falls in the range around the temperature of 181 K, corresponding to the γ relaxation transition of the PTFE. The wear of the fabric composites, the microstructure, and the chemical composition of the transfer film are comprehensively investigated. The results demonstrate that thermal activation and increased mechanical properties contribute to friction coefficient variation above and below the temperature of 181 K, respectively.