Effects of Accelerated Aging on SiO₂-Treated Wood Samples

Abstract

Wood is a viscoelastic composite material that has been historically prominent in the construction of buildings and continues to see widespread use. When used for exterior applications, wood is exposed to dynamic environmental conditions and can degrade if left untreated. Previous research by Lemaire-Paul et al. (2022) has proven that vacuum impregnation of the wood cell structure with a silica (SiO₂) nanoparticle colloid under a vacuum pressure of -90 kPa can enhance the viscoelastic properties, increase the density, and reduce the water uptake of white spruce wood. However, the behaviour of SiO₂-treated wood under different environmental conditions over time has yet to be fully explored. This research aims to examine the durability and performance of SiO₂-treated spruce wood samples subjected to accelerated aging conditions under high temperature and humidity as well as freeze-thaw cycling. Spruce wood samples were treated with 40% SiO₂ nanoparticle colloid under a vacuum pressure of -90 kPa. One set was placed in a hydrolytic aging chamber at 90°C and 80% RH. Another set was placed in a freeze-thaw cycling chamber that cycled from 25°C to -18°C and back at a rate of 6 cycles per day. The samples were removed at regular intervals and thermogravimetric analysis, dynamic mechanical analysis, tensiometry, X-Ray diffraction, and scanning electron microscopy were performed. When compared to the results obtained from a set of non-treated samples, it was found that the SiO₂-treated samples exhibited lower water uptake values that stabilized over time, as well as a lower rate of decrease in peak cellulose degradation temperatures under hydrolytic aging and a slight increase in peak cellulose degradation temperature over time under freeze-thaw aging. The effects of both aging conditions on the viscoelastic properties of the samples were also found to be insignificant. Both types of samples under both types of aging also exhibited an increase in crystallinity over time. These results indicate that the durability and properties of wood can be improved through nano-SiO₂ impregnation as the material remains relatively stable when subjected to high temperature and humidity conditions as well as freeze-thaw cycling over time.