Superlubricity of PTFE triggered by green ionic liquids

Abstract

Polytetrafluoroethylene (PTFE) is in the limelight due to its self-lubricating properties and outstanding corrosion resistance. Nevertheless, it suffers from severe adhesive and abrasive wear, resulting in barriers to the achievement of robust superlubricity and reliability of moving parts. Herein, two green protic ionic liquids (ILs) are synthesized using alkyl amine and carboxylic acids with long molecular chains, which are applied in PTFE/steel tribo-pair, showing a robust superlubricity under high contact pressure. Compared with conventional lubricating oils (PAO8, PAO10 and PEG400), as-prepared ILs show the lowest coefficients of friction less than 0.008, and the lowest wear volume of PTFE with the adhesive and abrasive wear of PTFE significantly inhibited. The excellent lubricating performance attributes to the thick and dense Stern layer as well as the formation of tribo-chemical film. This work, for the first time, achieves superlubricity on soft material substrates and guides the lubricants design for PTFE tribological applications.