Silanes for conservation of archaeological woods using modeled birch wood: antifungal, physical-chemical and TGA studies

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 similar to 90% (very-durable) and similar to 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.