Boric acid (BA) effectively controls wood-rotting fungi and termite attack but is readily leached out in outdoor exposure. A newly developed tannin-boron (TB) complex has been investigated to reduce BA leaching and to preserve beech plywood from biological attack. Wood veneers were impregnated with different TB solutions and then bonded with a melamine urea formaldehyde (MUF) adhesive for bond class 2 applications. The formation of a solid hydrophobic TB network on the veneer surfaces partially decreased the tensile shear strength of plywood but the prepared panels met the requirements for bond class 2. The plywood samples made from veneers treated with only BA solutions showed fair resistance against white rot fungus and termite attack, but the durability decreased even after mild leaching tests. The panels made of treated veneers with TB formulations showed instead a high resistance against biological attack after mild leaching and to some extent after severe leaching tests. This depended on the concentration of tannin and BA in the solutions. Favorable results were obtained with 20% tannin in the formulation. The results of the termites feeding choice test were more positive than those obtained by a forced feeding test. The control samples were attacked faster and showed higher weight loss when alternative samples included TB formulations.

Furfural (F) cannot be easily polymerized like furfuryl alcohol, but it is an aldehyde that can react with urea (U) to make a polymeric network. The possibility of preparing F/U polymer along with an acidic catalyzer (maleic anhydride; M) was evaluated as a means to improve some selected properties of birch (Betula pendula) wood. The F+U/M resin was introduced into the wood with a double treatment technology. The first step involved dilution of F in water and methanol, and the second step was immersion in a U/M aqueous solution. The color of treated wood was darkened after resin curing from brown to a spectrum of black depending on the amount of loaded resin. The 60 to 80% of materials were converted to a non-leachable polymer based on the different formulations. The water absorption and volumetric swelling of the treated samples decreased with an increase in weight percent gain (WPG). The analysis of mechanical strength showed that treatment with F + U/M reduced to some extent the hardness and the impact bending of wood, while modulus of rupture, modulus of elasticity, and compression parallel to the grain with WPG were increased. The exposure of the samples to the accelerated weathering showed noticeable changes in color and roughness.

Conservation of ancient wooden artifacts, in addition to consolidation advantage, prevent its deterioration over time. In this research, silane consolidants, including methyltrimethoxysilane (MTMS) and 3-mercaptopropyltrimethoxysilane (MPTMS) with 25 wt% in ethanol were applied under controlled conditions on modeled birch wood (Betula pendula) as a conservation strategy for archeological woods in terrestrial environments. While the wood samples were gradually saturated and dried, aesthetics and cell-walls integrity were also considered. The leaching characteristics, visual and physical changes of wood specimens were evaluated during 4 aging periods to assess their performance and stability. Morphological and chemical reactions were analyzed by FE-SEM microscopy and ATR-FTIR spectroscopy, respectively. For comparison, antifungal properties and thermogravimetric analysis (TGA, DTG) were also examined on the samples. As results, silanization reduced the wood-water interactions while maintaining the aesthetic properties, especially with MPTMS. Maximum water-repellency of silane-treated woods were achieved after a water post-treatment, which probably indicates the secondary hydrolysis of silanes in the presence of water and their re-polymerization. Biological-durability testing (according to EN 113-2) of birch wood (not-durable), against Basidiomycete fungi (i.e., Trametes versicolor and Gloeophyllum trabeum) showed ~ 90% (very-durable) and ~ 65% (moderately-durable) efficiency for MPTMS- and MTMS-treated wood respectively. Based on FTIR and TGA analysis, more interactions of MPTMS with lignin was found, which is more consistent with the chemical nature of most archaeological woods. Thermal-stability and low hygroscopicity of silane-reinforced woods were also confirmed by TGA/DTG, indicating high conservation potential of silanes for historical woods. Meanwhile, a complementary study on real ancient samples is recommended.

Sugarcane bagasse is an agro-waste that could replace timber resources for the production of bio-composites. Composite boards such as particleboard offer an issue for the use and recycling of poor quality timber, and these engineered products can overcome some solid wood limitations such as heterogeneity and dimension. Bagasse offers an alternative to wood chips for particleboard production but present some disadvantages as well, such as poor physico-mechanical properties. To address these issues, bagasse fibers were treated with an innovative natural resin formulated with tannin and furfural. Impregnated particles with different concentrations of resin (5%, 10%, and 15% m/m) were exposed to temperatures of 40°C, 60°C, 80°C, and 100°C for resin curing. Various types of tannin-based adhesives, including tannin formaldehyde, tannin/formaldehyde-furfural, and tannin hexamine, were utilized for bonding the treated bagasse particles. The resultant panels were assessed for their physical and mechanical properties and compared to those produced using Melamine-Urea-Formaldehyde (MUF) adhesive. The density of the panels varied from 650 to 730 kg/m³ depending on the resin concentration. The values for both modulus of elasticity and modulus of rupture increased as the resin concentration increased. The internal bonding values exhibited an increase with resin concentration up to a critical point, after which a decreasing trend was observed. The water absorption and thickness swelling were significantly reduced with an increase in resin concentration. However, the panels produced using MUF adhesive yielded the most favorable physico-mechanical properties. Additionally, the panels made with tannin-based adhesives met the minimum requirements specified in the standard EN 312 (specifications for uncoated resin-bonded particleboards) for application in dry conditions. The analysis of formaldehyde emissions indicated that panels produced with tannin-based adhesives exhibited significantly lower emissions compared to those made with MUF. The tannin/furfural resin showed great potential for improving the quality of bagasse particleboard using tannin-based adhesives.