ENHANCEMENT OF BIOLOGICAL AND PHYSICAL-PROPERTIES OF WOOD BY BORIC ACID-VINYL MONOMER COMBINATION TREATMENT

Boron treatment was combined with vinyl polymerization to improve leac hing resistance of boron from wood, as well as dimensional stability, biological and fire resistance of wood. Boric acid (BA) was impregnate d into wood specimens [sapwood of Cryptomeria japonica D. Don, 20 (T) x 20 (R) x 10 (L)mm] as 1% aqueous solution prior to vinyl monomer tre atment. Styrene (ST), methylmetacrylate (MMA) and their mixtures (50:5 0, v/v) were impregnated in the presence of a catalyzer and a crosslin ker. Polymerization was conducted by heat radiation method at 90 degre es C for 4 h. Treated specimens were then subjected to decay and termi te tests, as well as oxygen index (O.I.) determination. Anti-swelling efficiency (ASE;) and water absorption levels (WA) were also measured by standardized methods. Vinyl monomers succeeded in reducing WA of wo od to a minimum level and delay boron leaching considerably. The treat ed wood proved to be resistant against two decay fungi, Tyromyces palu stris and Coriolus versicolor and very destructive termite Coptotermes formosanus even after ten severe weathering cycles. BA increased the O.I. levels of monomer-treated wood, which resulted in a lower flame s pread index. Moreover, BA suppressed the smoke generation due to monom er cooperation in wood.