Several SiO2 wood-inorganic composites and their fire-resisting properties

Summary In a study on the SiO₂ wood-inorganic composites prepared by the sol-gel process with tetraethoxysilane (TEOS), it is more appropriate to use safer agents than TEOS, considering the operational and processing environments. In this study, therefore, methyltrimethoxysilane (MTMOS) was used to prepare the SiO₂ wood-inorganic composites, and comparative studies were made with TEOS. Resultingly, SiO₂ wood-inorganic composites could be successfully prepared from MTMOS reaction system, as in TEOS system, with its lower concentration, and both composites had SiO₂ gels specifically formed within the cell walls from moisture-conditioned wood specimens. On this SiO₂ composites, the water-repellent properties were added most effectively with a molar ratio of 2-heptadecafluorooctylethyltrimethoxysilane (HFOETMOS) to alcohol being 1/250 and 1/180 for TEOS and MTMOS reaction systems, respectively. On the other hand, fire-resisting properties were tried to add to SiO₂ composites with several fire-resisting agents. The fire-resisting agents in the obtained composites are not, however, stable and leached out readily. Therefore, a small addition of HFOETMOS was tested to the MTMOS and TEOS reaction systems with fire-resisting agents. The obtained results clearly indicated that HFOETMOS could restrain the fire-resisting agents to be leached from the composites, and that composites from MTMOS system were superior to TEOS system on the antileachability. Therefore, MTMOS can be appropriate for displacement of TEOS as a chemical agent to prepare SiO₂ wood-inorganic composites.This research has been performed in Department of Wood Science and Technology, Faculty of Agriculture, Kyoto University, Kyoto, Japan.This research was supported by a Grant-in-Aid for Scientific Research (B) (No. 06453176, 1994.4–1996.3) from the Ministry of Education, Science, and Culture, Japan.