Leaching characteristics, decay and termite resistance of treated wood with boron compounds, N'-N-(1,8-Naphthalyl) hydroxylamine (NHA-Na), and hydroxynaphthalimide (NHA-H)

IRG/WP 03-30307

S N Kartal, Y Imamura

Despite many advantages of boron wood preservatives, boron itself does not adequately protect wood in ground contact and exterior applications because its natural diffusibility and susceptibility to leaching. As a result of previous studies to limit or decrease boron leaching, several fixation systems have been developed. In this study, we evaluated the effects of N'-N-(1, 8-Naphthalyl) hydroxylamine (NHA-Na) and hydroxynaphthalimide (NHA-H) on boron leaching and decay and termite resistance via boron precipitation in wood after NHA treatments at varying concentrations. Wood blocks were treated with disodium octaborate tetrahydrate (DOT), boric acid (BA) NHA-Na or NHA-H solutions. Preliminary results showed treatment of wood blocks with DOT, boric acid, and calcium borate and 1% or 0.1% NHA-Na solutions in sequential processes appears to somewhat reduce the susceptibility of boron to leaching. Blocks treated sequentially with boron compounds and then 1% NHA-Na solutions showed about 30% less boron leaching. In addition, the existence of boron and NHA in wood together showed a synergetic effect against wood degrading organisms and termites. We conclude that precipitation of NHA at higher concentrations decreases or limits boron leaching. On the other hand, the relationship between boron and NHA concentration in wood as regards precipitation possibilities appears to be predictive for reducing boron leachability.

Keywords: Boron, leaching, DOT, boric acid, NHA, decay resistance, termite resistance

Conference: 03-05-18/23 Brisbane, Australia

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