Friction and wear properties of hybrid sol-gel nanocomposite coatings against steel: Influence of their intrinsic properties

A dual UV-curing process inducing in a single step cationic photopolymerization and a photoinduced sol-gel process was used to obtain novel hybrid coatings. For this, an epoxy resin based on hydrogenated diglycidyl ether bisphenol A was mixed with an epoxy trimethoxysilane precursor (GPTMS, TRIMO) in the presence of photoacid generator based on diaryliodonium salt. Various UV-cured coatings were prepared with different amounts of the hybrid monomer (20 and 50 wt%), and two thicknesses: 15 and 80 μm. The friction and wear properties of these coatings were characterized on a ball-on-disc tribometer (steel ball; applied normal load: 6 N; sliding speed: 5 cm/s). Both the coating thickness and the addition of the hybrid monomer tend to improve the stiffness of the pure epoxy resin; however, these two parameters also induce an increase of the dynamic friction value.