Bonding performance of hot-bonded acetylated beech ( Fagus sylvatica L.) laminated veneer lumber (LVL)

This study demonstrates acetylation with acetic anhydride, one of the few industrial wood modification techniques on the market, to increase the dimensional stability and durability of laminated veneer lumber (LVL) made from beech wood (Fagus sylvatica L.). After being acetylated, veneers were hot-bonded to LVL using phenol-formaldehyde resin (PF) or phenol-resorcinol-formaldehyde resin (PRF). The bonding performance (bonding shear strength (BSS) and wood failure (WF)) was tested under the following three conditions: 20°C and 65% RH, water immersion, and rigorous boiling-drying-boiling cycle. Additionally, using the same specimen sizes on a second sample set, the moisture content (MC) and dimensional stability were determined. Results indicate that the PRF resin provided the strongest bonding performance on acetylated LVL and references. Acetylated LVL had higher BSS in wet conditions than untreated controls, especially after boiling in water, which could be attributed to less wood-water interaction at the cell wall level after acetylation.