Abstract

We have assessed the effect on bonding performance of modifying synthetic wood adhesives. Wood samples were prepared from Scots pine (Pinus sylvestris L.) and oriental beech (Fagus orientalis L.). Samples were bonded using poly(vinyl acetate) (PVAc) and urea-formaldehyde (UF) adhesives modified with melamine-formaldehyde (MF) and phenol-formaldehyde (PF). Modified formulations included PVAc alone, PVAc + UF (at 15, 35 and 50% UF), UF alone, UF + MF (at 15, 35 and 50%), and UF + PF (at 15, 35 and 50% PF). Samples were exposed to three experimental environments: Standard atmosphere, cold water, and boiling water. For bonding strength determination, we used DIN 53 255 standard. We conclude that the adhesive modifications tested generally have no significant effect on bonding performance under standard atmospheric conditions, but do increase bonding performance under cold and boiling-water conditions. The best adhesive bonding strength was found using oriental beech samples with the UF + MF (50%) adhesive: 9.24 N/mm² bonding strength under standard atmosphere conditions, 6.06 N/mm² in cold water, and 4.39 N/mm² in boiling water.

Key words: Adhesive modification, poly(vinyl acetate) (PVAc), urea-formaldehyde (UF), melamine-formaldehyde (MF), phenol-formaldehyde (PF), bonding strength, bonding performance.