The aim of this study is to determine how tree species, their sapwood-to-heartwood ratios, adhesive type, and environmental conditions affect the bonding strength of the wood material. The bonding strengths formed by joining the sapwood and heartwood of chestnut (Castanea sativa Mill.), oak (Quercus petrea L.) and Scotch pine (Pinus sylvestris L.) with polyurethane, epoxy, and resorcinol formaldehyde adhesives are the focus of the study since these wood species and adhesives are used extensively in Turkey. The results of the study indicated that oak has the best bonding strength performance for all environmental conditions. It was determined that the bonding strengths of the sapwood specimens were higher than the bonding strength of the heartwood specimens for all environmental conditions. The best bonding strength was obtained by using the resorcinol formaldehyde adhesive, and this was followed by the epoxy and polyurethane adhesives for all environmental conditions. There were apparent decreases in the bonding strengths for all of the tree species and adhesives when the environmental conditions were more severe.

Key words: Adhesives for wood, epoxy, polyurethane, resorcinol formaldehyde, lap-shear.