Factors influencing timber gluability with one-part polyurethanes – studied with nine Australian timber species

Abstract The bulk and surface properties of blocks of nine Australian wood species of commercial importance were investigated to elucidate the factors affecting timber gluability with structural one-component polyurethane adhesives. Cross-lap joints were prepared from freshly sanded blocks and the joints were subjected to creep loading in a condensing humidity environment. The median tensile strength (MTS) of the joints was found to improve with decreasing phenolic extractives content, lower timber density and decreasing lipophilic surface extractives content. The latter was assessed from O/C atomic ratios of the timber surfaces determined by X-ray photoelectron spectroscopy (XPS). The content of bulk lipophilic extractives and lignins and wettability of the surface as determined by the sessile drop method did not reveal significant correlations with the adhesion properties. The adhesion tests indicated significant gluability differences between the species investigated.