International Journal of the Physical Sciences Vol. 6(2), pp. 294-300, 18 January, 2011 Available online at http://www.academicjournals.org/IJPS ISSN 1992 - 1950 ©2011 Academic Journals Full Length Research Paper Determination of bonding performance of several modified wood adhesives Mustafa Altinok 1 , Musa Atar 1 , Hakan Keskin 2 , Suleyman Korkut 3 * and Ilhan Kocaturk 1 1 Department of Furniture and Decoration, Faculty of Technical Education, Gazi University, 06500 Besevler, Ankara, Turkey. 2 Department of Industrial Technology, Industrial Arts Education Faculty, Gazi University, 06830 Gölbasi, Ankara, Turkey. 3 Department of Forest Industrial Engineering, Faculty of Forestry, Duzce University, Beciyorukler Campus, 81620 Duzce, Turkey. Accepted 22 December, 2010 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/mm 2 bonding strength under standard atmosphere conditions, 6.06 N/mm 2 in cold water, and 4.39 N/mm 2 in boiling water. Key words: Adhesive modification, poly(vinyl acetate) (PVAc), urea-formaldehyde (UF), melamine- formaldehyde (MF), phenol-formaldehyde (PF), bonding strength, bonding performance. INTRODUCTION Animal-based adhesives have been widely used in assorted industries for more than 300 years. Synthetic adhesives provide very important technical advantages to the woodworking industry. Synthetic adhesives are typically either thermoplastic or duroplastic in nature. Thermoplastic adhesives as PVAc are applied at ambient temperature (TS EN 205). Duroplastic adhesives are applied hot, in plasticized state, same as the thermoplastic adhesives, but they are not cross-linked at the time of application. Contrary to thermoplastics, these adhesives are not plasticized again when they are reheated. The process is not reversible. Studies have shown that the bonding characteristics of *Corresponding author. E-mail: suleymankorkut@hotmail.com. synthetic adhesives can be altered when modified with certain compounds. Plywood resistant to cold water can be produced using Wikol (super lackleim 308) and modified Wikol adhesives (DIN 53 255). Medium-density fibreboard (MDF) and plywood (between 3 and 9 mm thick), have been covered with oak, elm, teak, and Paulownia wood panels (0.25 mm thick) using poly(vinyl acetate) (PVAc), urea-formaldehyde (UF), and PVA/UF adhesive mixtures. The highest bonding strengths obtained were from PVA/UF adhesives (Gos et al., 1987). Samples bonded with UF adhesives modified with poly(vinyl alcohol) (1 to 2%) and amylum (10 to 15%) were tension tested and showed increased bonding strength (Suh et al., 1989). The UF adhesive was modified with poly(vinyl alcohol) and amylum to increase water resistance. The results indicated that the amount of free formaldehyde decreased and bonding strength