The impact of vacuum pressure on the effectiveness of SiO2 impregnation of spruce wood

Wood is a widely used construction material that has many advantageous properties. However, it suffers from weaknesses such as low-dimensional stability and low durability in humid environments. These issues are associated with the porous vascular structure of wood that leads to a high water uptake capacity. This research aims to reduce the water uptake capacity of spruce wood by dip-coating samples in an aqueous colloid of silicon dioxide (SiO2) nanoparticles. SiO2 is a dense ceramic material with good chemical stability. It is readily available and affordable, making it an excellent candidate for this application. This study investigates the effect of SiO2 impregnation on the physico-mechanical properties of spruce wood. Density measurements, water uptake tests, microscopy examination, thermogravimetric analysis, and dynamic mechanical analysis were conducted on non-treated and SiO2-treated spruce wood samples. Quantitative and qualitative analyses demonstrated that SiO2 impregnation performed under higher vacuum pressure was more effective compared to the atmospheric condition and exhibited a greater presence of SiO2 in the wood’s vascular system. SiO2 impregnation under vacuum pressure demonstrated an effective increase in the density of the wood. It also reduced the porosity, which led to a significant reduction in the water uptake of the spruce wood. The analysis of the wood viscoelastic properties revealed that SiO2 impregnation under atmospheric and vacuum conditions triggered two different reinforcing mechanisms. The results showed that a significant improvement of the spruce wood storage and loss moduli could be achieved when impregnation was performed at the highest vacuum pressure of − 90 kPa.