Surface properties of tannin treated wood during natural and artificial weathering

Abstract

Tannins are the natural substances that plants use to protect wood. Novel tannin based formulations were tested to evaluate their efficacy in preventing weathering degradation of the surfaces. Scots pine and European beech specimens were treated with flavonoid based wood preservatives and exposed to artificial and natural weathering. The surface properties of the samples before and after weathering were evaluated using contact angle and colour measurements. Tannin treated samples showed a moderate resistance against discoloration and greater wettability than untreated samples. ATR-FT-MIR and FT-NIR spectroscopies combined with principal component analysis (PCA) revealed that weathering mainly degrades the aromatic component of wood. Because the protective tannin network is nothing more than an aromatic polymer, it suffers a similar degradation of lignin. Although the higher amount of aromatics leads to higher degradations, it is still possible to observe via vibrational spectroscopies that the flavonoid enriched surfaces contain more aromatics also after weathering.