Friction-reducing and wear-resistant cellulose-epoxy composite coating based on fish-scale biomimetic structures

Abstract

Epoxy resin (EP) coatings are attractive for surface protection because of their strong adhesion and chemical stability; however, their intrinsic brittleness and limited tribological durability, together with filler agglomeration and weak filler–matrix interfaces, restrict their performance under sustained sliding contact. Herein, inspired by the hierarchical architecture of fish scales, a biomimetic cellulose/ionic liquid crystal/Mica reinforcement system was constructed in EP coatings through a facile casting strategy. In this design, cellulose nanofibrils (CNF) form a load-supporting fibrous framework, mica provides scale-like lamellae with low-shear interlayer sliding, and the ionic liquid crystal (ILc) acts as a dispersion and interfacial-regulating component. Unlike conventional single-filler reinforcement, this multiscale architecture integrates structural support, lamellar lubrication, and interfacial regulation within one coating system. The optimized CIM 15% -EP coating exhibited an ultralow average friction coefficient of 0.21, markedly lower than those of Mica 10% —EP (0.76) and Pure-EP (0.79). Meanwhile, its wear-track width was reduced by 68.7% and 72.9% relative to Pure-EP and Mica 10% -EP, respectively. The enhanced tribological performance is attributed to the synergistic effects of the CNF-supported framework, improved filler–matrix interfacial integration, and interlayer sliding of lamellar mica. As a supplementary assessment of coating integrity, electrochemical impedance spectroscopy in 3.5 wt% NaCl showed a relatively higher impedance modulus and broader capacitive response for CIM 15% -EP, consistent with moderately improved resistance to electrolyte ingress. These results demonstrate an architecture- and interface-mediated strategy for developing wear-resistant and self-lubricating EP composite coatings, with improved electrolyte-barrier integrity as an ancillary benefit.