TREATMENT OF PARTICLEBOARD CHIPS WITH ALKENYL SUCCINIC ANHYDRIDE

Wood chips were first sprayed with pure alkenyl succinic anhydride (3 % wt/wt) and then cured (130 degrees C. h(-1)) with the objective to impart water repellency to UF-bonded particleboards. Unlike conventionally used paraffin wax, the anhydride can be covalently anchored to the chip surface by esterifying wood hydroxyl groups; however, the treatment resulted in increased thickness swelling (67%) after 2 h water submersion and decreased internal bond strength (IB; 0.10 N mm(-2)) as compared to controls (21 % and 0.95 N mm(-2)). Wettability studies revealed that the surface polarity was increased after the anhydride treatment. FTIR analyses before and after extraction of non-bonded anhydrides showed that esterification did not occur during the curing step. Viscosity measurements indicated that the non-bonded anhydride on the chip surface was hydrolyzed to a dicarboxylic acid by the aqueous glue, which in turn induced premature condensation before pressing and affected bonding. Investigations on veneer strips suggested that an esterification requires a solvent to provide the anhydride certain mobility for orientation. The hydrophobicity of pure alkenyl succinic anhydride seems to impair the attachment to wood hydroxyl groups and the spreading over the polar chip surface.