The Viscoelastic Behaviour of Waterlogged Archaeological Wood Treated with Methyltrimethoxysilane

Abstract

Waterlogged wood treatment with methyltrimethoxysilane (MTMS) proved effective in stabilising wood dimensions upon drying (anti-shrink efficiency of 76–93%). Before the method can be proposed as a reliable conservation treatment, further research is required that includes the evaluation of the mechanical properties of treated wood. The aim of the study was to characterise the effect of the treatment on the viscoelastic behaviour of archaeological waterlogged elm and oak wood differing in the degree of degradation. Dynamic mechanical analysis in the temperature range from −150 to +150 °C was used for the study. To better understand the viscoelastic behaviour of the treated wood, pore structure and moisture properties were also investigated using Scanning Electron Microscopy, nitrogen sorption, and Dynamic Vapour Sorption. The results clearly show that methyltrimethoxysilane not only prevents collapse and distortions of the degraded cell walls and decreases wood hygroscopicity (by more than half for highly degraded wood), but also reinforces the mechanical strength by increasing stiffness and resistance to deformation for heavily degraded wood (with an increase in storage modulus). However, the MTMS also has a plasticising effect on treated wood, as observed in the increased value of loss modulus and introduction of a new tan δ peak). On the one hand, methyltrimethoxysilane reduces wood hygroscopicity that reflects in lower wood moisture content, thus limiting the plasticising effect of water on wood polymers, but on the other hand, as a polymer itself, it contributes to the viscous behaviour of the treated wood. Interestingly, the effect of silane differs with both the wood species and the degree of wood degradation.

Imaging and Assessment of the Microstructure of Conserved Archaeological Pine

“…In the case of methyltrimethoxysilane, for example, the surface area and total pore volume decrease in proportion to the amount of methyltrimethoxysilane incorporated. In addition, depending on the degree of degradation and the type of wood, methyltrimethoxysilane shows a softening effect as well as the reduction of moisture content in the wood [84]. The deposition of the chemical into the cell wall and amorphous aggregates in the lumen areas was observed [86].…”

“…Appendix A Table A1). Currently, a lot of research on the treatment of silanes and siloxanes has been undertaken [34,[84][85][86]. However, it could be shown that the stabilizing effectiveness and their deposition in the wood structure of particular organosilicons is dependent on their chemical composition [34].…”

Consolidation and Dehydration Effects of Mildly Degraded Wood from Luoyang Canal No. 1 Ancient Ship

“…The wood treated with trehalose (Tre) demonstrated the highest compressive strength at 69.54 MPa, indicating a significant enhancement in strength due to the trehalose treatment. In contrast, the wood treated with Trimethoxymethylsilane (MTMS) showed a lower compressive strength of 51.49 MPa compared to the trehalose-treated and healthy wood samples [41]. Figure 3 illustrates the visual effects of the MTMS and trehalose treatments on the waterlogged wood samples compared to the untreated samples.…”

Sustainability in Heritage Wood Conservation: Challenges and Directions for Future Research

“…Lastly, alkoxysilanes are a relatively new addition to the wood conservation toolkit but have gained increasing popularity in recent years [111][112][113][114]. Alkoxysilanes have already been heavily used in the waterproofing and fire retardancy of construction wood, particularly for external applications, so their transfer into the conservation field is not surprising [115][116][117].…”