A boron-containing ternary-treatment system to improve the performance of Cathay poplar in outdoor applications

Abstract

ABSTRACT Inorganic borates are effective against the attacks from wood decay fungi and termites; however, they are inclined to leach out during outdoor service. In order to improve boron leaching resistance, and enhance the overall performance of wood, including the resistance against decay fungi and termites, dimensional stability, and alleviate the toughness loss caused by furfurylation, a ternary-treatment system composed of disodium octaborate tetrahydrate (DOT), furfuryl alcohol (FA) and polyvinyl alcohol (PVA) is proposed and impregnate wood in a two-step process in this study. Results of boron analysis by the inductively coupled plasma-atomic emission spectroscopy (ICP-AES) show that the leaching rate of boron of DOT/FA/PVA treated wood is intensively slowed down, especially during the initial period. Decay resistance of DOT/FA/PVA treated wood against both white rot fungi Coriolus versicolor and brown rot fungi Gloeophyllum trabeum still shows promising results after leaching tests, respectively 1.33% and 1.71%. Compared with DOT-treated wood, the combinations with FA can provide better protection against termites and greatly improve dimensional stability, but PVA shows a little negative effect on termite resistance. Nevertheless, PVA can alleviate the reduction of impact toughness due to furfurylation to a certain extent. In summarization, the combination system of DOT/FA/PVA should be a promising protection approach for wood used for outdoor applications.