In Europe, boron compounds are facing restrictions, and due to their natural solubility into water, the only way to keep using them for wood protection is to fix them into the wood, at very low level (Obanda et al. 2008). In the meantime, the idea of protecting wood with natural preservatives has been back into favour (Lotz and Hollaway 1988, Nakayama et al. 2001, Singh and Singh 2012). Tannin a natural plant extract, can be linked with boron (in the form of boric acid) into treated wood, without affecting boron biological activity. Moreover, adding hexamine in the formulation allows waterproofing the tannin-boron system within treated timber. Tannin-boron-hexamine association have shown their efficacy in laboratory tests (Thevenon et al. 2009, Tondi et al. 2012a). Despite good biological activity, the tannin based polymer remains very rigid and has a tendency to cracks. The idea of adding ɛ-caprolactam to the original formulation (tannin-boron-hexamine) is to obtain a more elastic polymer (Tondi et al. 2012b). This so-called “advanced tannin-boron association” with ɛ-caprolactam has also been proved to anchor more boron in wood (Hu, 2015). This study reports the results of advanced tannin-boron formulations in the case of unsterile soil bed tests.

Download document (614 kb)
free for the members of IRG. Available if purchased.

Purchase this document