Wood and its derivatives: Sustainable materials and products for future needs sections VI: Wood preservation, environment. Environmentally friendly wood protection based on tannin resin-boric acid association for outdoor long-time uses

Boron compounds are widely used in the field of wood preservatives as they can act as both fungi( ide and insecticide (even against termites) and present many other qualities like being odourless, colourless, non flammable, etc.... Nevertheless, in the field of wood protection, borates are considered for indoor uses only or in association with other biocides when for outdoor exposure. due to their main disadvantage of being readily leachable from treated wood. To overcome this problem, boric acid was fixed into wood with condensed tannins and hexamine through a non-formaldehyde emission polymer network. Different treated mixtures were tested with proportion of mimosa tannins and hexamine, added or not with boric acid, which concentration remained below the EU authorized levels. Such treated beech samples were leached and tested according to the guidelines of European Standard EN 113 against Pycnoporus sanguineus in tropical conditions. These systems proved their efficiency against boron depletion and fungal decay meeting the efficacy requirements of EN 113. Thus, such assoc ations could be envisaged to treat tropical timber with insufficient natural durability for above ground outdoor use, and for a long service-life of the wooden commodities. (Texte intégral