Comparison of physical and thermal properties of various wood-inorganic composites (WICs) derived by the sol-gel process

Abstract

AbstractThe physical properties and thermal decomposition kinetics of wood-inorganic composites (WICs) were in focus, which were prepared from methyltriethoxysilane (MTEOS), tetraethoxysilane (TEOS) and titanium (IV) isopropoxide (TTIP) by the sol-gel process. The hydrophobicity and dimensional stability of the composites were better than those of unmodified wood (Wcontr), but the performance of SiO2-based WICs (WICSiO2) was the best. The SEM-EDX micrographs show that silica is only distributed within the cell wall of the WICSiO2. By contrast, titania was deposited principally in the cell lumens of the WICTiO2. The thermal decomposition kinetic experiments show that the average apparent activation energies with conversion rates between 10% and 70% were 156–168 (Wcontr), 178–180 (WICMTEOS), 198–214 (WICTEOS) and 199–204 (WICTTIP) kJ mol−1at the impregnation level of 20% weight gain. The reaction order values calculated based on the Avrami theory were 0.51–0.57, 0.39–0.51, 0.36–0.47 and 0.28–0.51 in the same order of species indicated above. Accordingly, the dimensional and thermal stability of the wood could be enhanced effectively by the sol-gel process with silicon- and titanium-based alkoxides.