Improving compatibility and tribological performance via supramolecular gelation of MoS2 nanoparticles in Perfluoropolyether lubricants

Abstract

Perfluoropolyether (PFPE) oils pose challenges in their compatibility with nanoparticle lubrication additives due to their unique molecular structure, limiting their lubrication performance enhancement. To address this issue, we propose the development of nanoparticle composite supramolecular gel lubricants, aiming to maintain the dispersion stability of molybdenum disulfide (MoS₂) nanoparticles within PFPE lubricants. It was achieved by harnessing the self-assembled three-dimensional network structure of supramolecular gels to entrap MoS₂ nanoparticles. It was observed that MoS₂ nanoparticles tended to cluster and settle in PFPE oils. However, the MoS₂-composite PFPE supramolecular gel lubricant (gel@MoS₂) exhibited exceptional dispersion stability over an extended period. MoS₂ nanoparticles used as additives in PFPE-based supramolecular gel lubricants not only enhanced mechanical strength but also retained outstanding thixotropic properties. Additionally, nanoparticles improved extreme pressure performance, anti-friction capabilities and anti-wear properties of PFPE-based supramolecular gel lubricants under high loads of 300N. Furthermore, the lubrication mechanism of gel@MoS₂ composites was elucidated using focused ion beam-transmission electron microscopy and X-ray photoelectron spectroscopy. During the friction process, the 3D networks of supramolecular gels, held together by weak interaction forces like H-bonds, halogen bonding, and van der Waals forces, were disrupted under continuous shear forces. Consequently, some of the MoS₂ nanoparticles and gelators migrated to the steel surface, forming a protective lubricating film. This research holds significant importance in prolonging the lifespan of equipment in critical sectors such as aerospace and aviation, where high-end lubrication is essential.