Impregnations using Silicon-containing Compounds

3 Impregnations using Silicon-containing Compounds 7.3.1 Inorganic Silane Impregnations 

Zollfrank (2001) reacted beech wood with trimethylsilyl chloride under anhydrous conditions in tetrahydrofuran in the presence of pyridine. Pyridine was present to scavenge the HCl produced during the reaction, thus limiting polysaccharide degradation. After reaction at room temperature for 12 hours, the wood was extracted with methanol to remove the pyridinium chloride by-product. SEM of the modified wood indicated that there was no evidence of cell wall degradation. 

Miyafuji and Saka (2001) treated moisture-conditioned wood with a methanolic solution of MTMS in combination with sodium ethoxide, or sodium acetate, to form Na20-Si02 gels. The gels were found to be mainly located in the cell wall and improved the fire resistance of the wood. The use of benzophenone in combination with a Si-gel treatment has been fonnd to improve the UV stability of wood (Miyafuji etal. 2004). 

Hager (1995), noting that water-based silicone systems had been used on masonry and concrete to provide water repeUency, investigated their potential as wood protection agents. He mentioned the work of E.G. Rochow, who built a house in 1958 using cedar that was treated with a silicone solution as a water repellent. After 28 years, the silicone protective layer was still sound. Hager treated wood with water-based silicone microemulsions and found that good water repellency could be obtained. 

Rozman etal. (1997a) treated rubberwood by impregnation with a methanolic solution of TMPS for 24 hours, followed by curing at 110°C for 5 hours. No solvent extraction was employed after treatment. Volume increases due to treatment were considerably lower than predicted theoretically, showing that little cell wall penetration had occurred. ASE measurements were made over two cycles, and it was found that ASE increased in the second cycle. This odd behaviour was not explained and the experimental details for ASE determination were not given. 

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