Flavanoid biocides: Wood preservatives based on condensed tannins

Abstract

The condensed tannins are natural wood preservatives found in high concentrations in the bark and wood of some tree species. Condensed tannin-containing bark extracts from loblolly pine (Pinus taeda) were evaluated as wood preservatives using standard methods. Bark extracts by themselves did not cause any reduction in weight loss of pressure-treated wood blocks at the retentions tested. However, they do have efficacy as wood preservatives when complexed with copper(II) ions. The best experimental wood preservative formulation was a dual treatment using a sulphited bark extract first, followed by a CuCl₂ treatment. At some retentions, this method yielded wood blocks with greater resistance to decay by Coriolus versicolor than pentachlorophenol. A single stage treatment of extract plus copper using an aqueous ammoniacal solvent was also successful but not as effective as the dual treatment.

Keywords

Wood preservative, procyanidin, bark extract, chelate, condensed tannin, copper, loblolly pine, Pinus taeda, Gloeophyllum trabeum, Coriolus versicolor

Citation

Laks, Peter; McKaig, Peggy A.; Hemingway, Richard W. 1988. Flavanoid biocides: Wood preservatives based on condensed tannins. Holzforschung 42(5):299-306