ENHANCEMENT OF LEACH AND TERMITE RESISTANCES OF PLYWOOD TREATED WITH BORIC COMPOUNDS

Fire retardant chemicals composed of trimethylol melamine (TM) -boric acid (B) or -phosphoric (P) and/or -dicyandiamide (D) were applied to the surfaces of plywood followed by hot pressing. The effectiveness of these various treatments were evaluated based on the incombustibility , leachability, and termite resistance of the treated plywoods. All tr eated specimens had better fire-retardant properties than the untreate d ones, and similar improvement were observed even after a deteriorati ve pretreatment of dipping in 50 degrees C warm water for 30 minutes p rior to testing. The specimens treated with TMP combinations had bette r improvements in the incombustible properties, in terms of ignition t ime, after-flaming time, glowing time, weight loss, and char length. U nleached specimens treated with boric acid had the best termite resist ance, followed by TMB and TMDB combinations. In all cases, trimethylol melamine appeared to have a profound effect in keeping the damage to lower levels after leaching. Observation by ion chromatography reveale d that trimethylol melamine was effective in slowing down boron and ph osphorus leaching even after several cycles of a severe leaching proce dure.