Bonding strength and dimentional stability of laminated veneer lumbers manufactured by using different adhesives after the steam test

Abstract

Composite materials manufactured from woods with different adhesives are being used increasingly in the construction of furniture frames and buildings. Yet there is little information available concerning the dimensional stabilization and shear strength of laminated veneer lumbers (LVL) after being exposed to steam. In this study, LVLS were manufactured from pine ( Pinus sylvestris L) and Black sea fir ( Abies nordmanniana) veneers with Phenol-formaldehyde (PF), poly (vinyl acetate) (PVAc), Desmodur-VTKA (D-VTKA) and urea-formaldehyde (UF) adhesives. Dimensional stability of LVL were measured after being exposed to steam for 2, 6, 12, 24, 48 and 96-h-period according to the procedure of the Turkish Standards (TS) 3639, then shear strength tests were applied (based on BS EN 205). As a result, the highest density was determined for LVL with UF adhesive in both samples. The highest weight increment as 57.53% for black sea fir LVL with PF, the highest radial swelling as 9.74% for pine LVL with PF, the highest tangential swelling as 4.1% for pine LVL with VTKA and the highest longitudinal swelling as 0.44% for pine LVL with PF adhesive were determined after being exposed to 96 h steam. The highest shear strength was obtained in pine control samples with VTKA adhesive (5.36 N/mm 2) and the lowest shear strength was obtained in Black sea fir LVL with PVAc adhesive (4.48 N/mm 2).