Preservative properties of vapor-boron-treated wood and wood-based composites

Abstract

The treatability of wood (sapwood of Cryptomeria japonica D. Don) and wood-based composites (particleboard, waferboard, medium-density fiberboard, plywood) with vapor-boron was good, and the treated materials proved to be resistant to decay fungi and subterranean termites in laboratory bioassays. No difference in effectiveness was noted between vapor-boron and liquid-boron treatment of wood. Toxic threshold values determined for solid wood were 0%-0.24%, 0.26%-0.51%, and 0.26%-0.51% BAE (boric acid equivalent), respectively, against the white-rot fungus Trametes versicolor (L.: Fr.) Pilat, the brown-rot fungus Fomitopsis palustris (Berk. et Curt.), and the subterranean termite Coptotermes formosanus Shiraki. A concentration of less than 1% BAE seemed sufficient to control biological attacks on composites, although the toxic limits could not be determined more accurately because of the tested range of boron retention. High boron retention was needed to meet the performance requirements for slow-burning materials when a fire-retardant agent was not incorporated into the glue line.