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

Improving the oil retention capacity while maintaining mechanical stability remains pivotal in the development of advanced oil-containing composite coatings. In this study, oxidized graphene-functionalized composite lithium soap fibers (CLF/PG), which exhibit 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 resulting in a composite coating (C-G/EP). Notably, the 1.0 wt% C-G/EP sample exhibited a wear rate of only 0.212×10⁻⁵ mm³/(N·m) after 80,000 friction cycles—a remarkable 98.14% reduction compared with that of the EP sample. Concurrently, the system maintained a stable average friction coefficient of ~0.031. Molecular dynamics simulations revealed that oil microdroplet integration within the hydrogen-bonded network simultaneously increased the bulk and shear moduli while reducing the Young’s modulus. The modulus reconfiguration facilitates a transition from rigid contact to microelastic deformation behavior at friction interfaces. This deformation behavior, synergizing with the load-bearing abilities of composite lithium soap fibers (CLFs) and aminated graphene oxide (PG), enhances the strength of the lubrication film, thereby shifting the lubrication state of C-G/EP from boundary lubrication to elastohydrodynamic lubrication. This work provides fundamental insights for designing high-performance self-lubricating coatings based on liquid fillers.