Oil microdroplet-containing epoxy composite coatings enhanced via hydrogen bonds for long-lasting lubrication protection

Abstract

The challenge of improving oil retention capacity while maintaining mechanical stability remains pivotal in developing advanced oil-containing composite coatings. Herein, oxidized graphene-functionalized composite lithium soap fibers (CLF/PG), exhibiting high oil affinity, were utilized to form a hydrogen bond network with epoxy resin (EP), constructing an effective oil retention network. By integrating dynamic micellar loading-desorption technology with a dual-spray gun system, we achieved uniform dispersion of oil microdroplets (G2825) within the oil retention network, ultimately fabricating a composite coating (C-G/EP). Notably, the 1.0 wt.% C-G/EP exhibited a wear rate of merely 0.212×10⁻⁵ mm³/N·m after 80,000 friction cycles - a remarkable 98.14% reduction compared with EP. Concurrently, the system maintained a stable average friction coefficient of ~0.031. Molecular dynamics simulations revealed that oil microdroplets integration within the hydrogen-bonded network simultaneously enhanced bulk and shear moduli while reducing Young’s modulus. The modulus reconfiguration facilitates a transition from rigid contact to micro-elastic deformation behavior at friction interfaces. This deformation behavior, synergizing with the load-bearing abilities of CLF and PG, enhances the lubrication film’s strength, thereby shifting C-G/EP’s lubrication state from boundary lubrication to elastohydrodynamic lubrication. This work provides fundamental insights for designing high-performance self-lubricating coatings based on liquid fillers.