Performance of boron-ethanolamine-quaternary ammonium based wood preservatives against leaching, wood decay and blue stain fungi

Abstract

Importance of boron compounds is increasing due to their low environmental impact, high efficacy and fact that many other active ingredients have been removed from the market after introduction of the Biocidal products directive. Borates are very effective against wood decay fungi; unfortunately they leach out of wood in wet environment. In order to improve their fixation, solubility and efficacy, borax and boric acid were combined with ethanolamine and quaternary ammonium compound. Afterwards, Norway spruce (Picea abies) specimens were impregnated with aqueous solutions and exposed to three wood decay fungi (Antrodia vaillantii, Gloeophyllum trabeum and Trametes versicolor) according to EN 113 procedure. Half of the specimens were leached prior exposure. Fixation of testing formulation in samples was determined as proposed by ENV 1250-2 standard. In parallel efficacy against blue stain fungi (Aureobasidium pullulans and Sclerophoma pithyophila) were determined as well according to 152 EN standard. The results showed, that addition of ethanolamine slightly improves boron fixation. Wood impregnated with preservative solutions of the lowest concentration (cB = cquat = 0.1%) was resistant against wood decay fungi. However, to ensure efficacy against blue stain fungi five or ten times more concentrated solutions needs to be used.