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The reaction of citric acid with wood veneers was studied by Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CP MAS 13C NMR) and matrix assisted laser desorption ionization time of flight (MALDI ToF) mass spectrometry. The analysis showed that reactions of citric acid occurred with both lignin and carbohydrate constituents of wood. The reactions occurring are esterifications between the carboxylic acid functions of citric acid and the numerous aromatic and aliphatic hydroxyl groups of the main wood constituents. Reaction of citric acid with glucose as a simple model compound of carbohydrates hydroxyl groups also yielded reactions leading to linear and branched oligomers by esterification. The result indicate that the reactions of esterification are accompanied in parallel by some internal rearrangements of lignin. The applied results on bonding wide flat wood surfaces such as veneers to obtain LVL panels yielded excellent strength results even if the conditions of pressing were more drastic than what is usual for this application. The applied bonding results have shown that citric acid has great potential to be used as a bio-binder for wood veneers.

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Thermomechanical modification is a technique that allows wood densification, improving mechanical properties and reducing hygroscopicity. In veneers, this technique is commonly used to improve bonding quality in wood based panels. This study aimed to evaluate the effect of thermomechanical modification on some physical properties of rotary peeled veneers of amescla (Trattinnickia burseraefolia). Veneers were treated in a hydraulic press at 140 and 180uC, for 1 and 2 min at 2?7 N mm 22 pressure. The apparent density was evaluated as well compression ratio, weight loss, equilibrium moisture content, thickness swelling and water absorption. The results showed that apparent density and compression ratio increased after treatment. Equilibrium moisture content values were lower in samples treated at 180uC. Dimensional stability was not improved due to release of compressive stresses. The surface of veneers was modified and its roughness and wettability were reduced significantly.