Wood surface preparation by silane Nano film formation using sol-gel method to improve the adhesion of alkyd and polyurethane coatings

In this research, the effect of Silane nanofilm formation using sol-gel method on improving the adhesion of Alkyd and Polyurethane coatings to wood surface in urban furniture was investigated. For this purpose, the surface of spruce wood (Picea abies L.) was modified with Tetraethoxy¬silane (T) and glycidoxy¬propyl¬trimethoxy¬silane (G) sol-gel materials. Then, solvent-borne alkyd (AS), solvent-borne polyurethane (PS) and waterborne polyurethane (PW) coatings were applied. Microscopic observation by fluorescence, confocal laser scanning microscopy (CLSM) and SEM showed that the silica component of nanosol covered the whole wood surface homogeneously, while alkyd and polyurethane coatings were deposited preferentially in the surface depressions. The combined analysis of ATR-FTIR, XRD and XPS demonstrated that the surface was covered with silicon oxides (SiO2) attached to hydrocarbon chains. The results of accelerated weathering test showed that the surface modification by sol-gel improved the weathering resistance of top coatings and reduced their roughness. The silane-based materials improved the adhesion and abrasion resistance properties, and Tetraethoxy¬silane had a better performance in comparison with glycidoxy-propyl¬trimethoxy¬silane. Among coatings, the highest tensile strength was observed for waterborne polyurethane. Solvent-borne alkyd showed the lowest tensile strength. Overall, the sol-gel derived hybrid inorganic–organic thin film was found to enhance the adhesion strength of coatings to wood surface and improve the weathering resistance of wood.