Reducing moisture swell of densified wood with polycarboxylic acid resin

A water-soluble polycarboxylic acid (PCA) resin was assessed for ability to limit moisture swelling of densified wood. Aspen flakes were treated in 0 (control), 1, 5, 10, and 20% PCA resin solutions and drained for 1, 10, and 20-min time periods. Following treatments, flakes were compressed to rough ly 50% strain at 170 degreesC. The: PCA content of flakes significantly inc reased with increasing concentration and drain time. Water absorption and t hickness swell of flakes decreased with increasing PCA content. Both water absorption and thickness swell of untreated flakes were over 100%; but for PCA-treated flakes, water absorption and thickness swell as low as 45% and 16%, respectively, were achieved. Irreversible thickness swell decreased wi th increasing PCA content, while reversible thickness swell remained relati vely constant. The swelling coefficient decreased with increasing PCA conte nt, a behavior that often is associated with bulking agents for treated, un compressed wood. However, dynamic mechanical analysis further suggested tha t PCA resin acts as a cross-linking agent to stabilize the position of the collapsed cell walls.