Modification of Wood by Tannin-Furfuryl Alcohol Resins–Effect on Dimensional Stability, Mechanical Properties and Decay Durability

Abstract

Furfurylation is a well-known wood modification technology. This paper studied the effect of tannin addition on the wood furfurylation. Three kinds of dicarboxylic acids, adipic acid, succinic acid, and tartaric acid, as well as glyoxal as a comparing agent, were used to catalyse the polymerisation of furanic or tannin-furanic solutions during wood modification. Impregnation of furanic or tannin-furanic solution at a certain concentration into the wood followed with curing at 103°C for a specific duration was performed for the wood modification. Different properties of the modified woods like dimensional stability, resistance of treatment to leaching, mechanical properties, decay durability against white-rot (Coriolus versicolor, Pycnoporus sanguineus) and brown-rot (Coniophora puteana) as well as their chemical and anatomical characteristics were evaluated. Results revealed that the partial substitution of FA by the tannins improved the fixation of the chemicals impregnated in wood. Further, dimensional stability, leaching resistance, Brinell hardness, modulus of elasticity/modulus of rupture, and decay durability properties of the furfurylated wood were also improved in the presence of tannins. Scanning electron microscopy revealed the deposition of the polymer in the wood lumen cells and in the wood cell walls.

Effect of Tannins Addition on Thermal Stability of Furfurylated Wood

“…Related to this type of treatment, and considering that the polymerization of furfuryl alcohol depends on several factors, including the nature and the concentration of the catalyst used and the concentration of FA solution [13][14][15], it seems interesting to evaluate the effects of the addition of condensed tannins as a reticulating agent, and of different types of acids as catalysts, to improve the properties of modified wood. The effect of such treatments on the mechanical properties and decay durability of modified woods have been already described in a previous study [16]. The aim of the present paper is to report the effects of the additions of tannins on the polymerization of furfuryl alcohol and on the thermal stability of the polymer.…”

“…Treated and untreated wood samples (5 mm × 20 mm × 20 mm, n = 18-30) were placed in different flasks containing a volume of water at least five-fold their volume. Flasks were placed on a plate stirrer and subjected to different leaching periods (1,2,4,8,16, and 48 h) with a change of water between each period. The wood samples were kept without water for 16 h after the period of 4 h. At the end of the leaching periods, the wood samples were dried at 103 • C for 48 h and weighed (m 3 ).…”