Silane nanofilm formation by sol-gel processes for promoting adhesion of waterborne and solvent-borne coatings to wood surface

The objective of this study was to promote the adhesion of waterborne and solvent-borne coatings [polyurethane (PU) and alkyd] on wood surfaces by silane nanofilm formation by means of sol-gel processes. Tetraethoxysilane and glycidoxypropyltrimethoxysilane served as sol-gel materials. The silane-based materials improved the adhesion strength. The positive effects can be explained by the changes in the wood surface chemistry induced by the sol-gel process. High-resolution X-ray photoelectron spectroscopy (XPS) showed an increase in -C-H and -C-C bonds and a decrease in -C-O bond. Microscopic observation by fluorescence and confocal laser scanning microscopy together with NIS-Elements analysis software showed that the silica component of nanosol covered the whole wood surface homogeneously, whereas alkyd and PU coatings were deposited preferentially in the surface depressions. The combined analysis of energy-dispersive X-ray analysis and XPS demonstrated that the surface was covered with silicon oxides (SiO2) attached to hydrocarbon chains.