Effects of the steam test on bonding strength of laminated veneer lumbers manufactured by using different adhesives

摘要

Failures in adhesion of wood particles or fiber in a composite board can result from several factors. Poor chemical and physical interfacial interactions between the wood surface and the resin and dissimilar swelling of resin and wood resulting from moisture sorption are two of the most important mechanisms of bond failure. This study was performed to determine how the adhesives affect shear strength of laminated veneer lumbers (LVL) manufactured from poplar, beech, pine, black sea fir, and quercus veneers, with phenol-formaldehyde (PF), poly(vinyl acetate) (PVAc), Desmodur-VTKA (D-VTKA), and urea-formaldehyde (UF) adhesives. The shear strength tests were done (based on BS EN 205) on the LVL, after being exposed to steam for 96-h period, according to the procedure of the Turkish Standards (TS) 3639. From the shear strength test, it was found that the hi-hest shear strength was obtained in beech control samples (not exposed to steam) with PVAc adhesive (15.8 N/mm(2)) and the lowest shear strength was obtained in poplar LVL with UF adhesive (4.24 N/mm(2)). Beech wood and VTKA and PVAc adhesives could be proposed for manufacturing of LVL used in wet conditions and exposed to shear strain. (c) 2006 Wiley Periodicals, Inc.