Microstructure of PTFE-Based Polymer Blends and Their Tribological Behaviors Under Aqueous Environment

Abstract

Four polytetrafluoroethylene-based polymer blends (PTFE blends) with polyimide (PI), polyether ether ketone (PEEK), poly(phenyl p-hydroxybenzoate) (PHBA), and perfluoroethylene propylene copolymer (FEP) were prepared by compression molding and follow-up sintering. Their microstructure was observed by scanning electron microscope. And the tribological behaviors of PTFE blends sliding against 316 steel under pure water and sea water lubrication were comparatively evaluated using block-on-ring tribology test rig. The worn surface of counterpart was examined by X-ray photoelectron spectroscopy. The results showed that by blending with the four polymers, PTFE exhibited the transformed microstructure and improved wear resistance. Compared with FEP, rigid polymers PI, PHBA, and PEEK can enhance the wear resistance of PTFE greatly because they can effectively improve the load-carrying capacity of PTFE matrix and can more efficiently prevent the crystalline bands of PTFE from being pulled out. However, because of the weak inhibition on the pulling out of PTFE crystalline bands, FEP cannot enhance the wear resistance of PTFE as significantly as other polymers. In addition, the friction coefficients and wear rates of PTFE and its blends were lower under the lubrication of sea water than under the lubrication of pure water, which was ascribed to more excellent lubricating effect of sea water originating from the deposition of CaCO3 and Mg(OH)2 onto the sliding surfaces.