Silica-Acrylic Nanocomposite Coatings for Durable and Hydrophobic Wood

Wood strength, renewability and appearance make it one of the most preferred and widely used natural materials in structural and cultural applications. The gradual degradation of wood from abiotic and biotic factors has an adverse impact on its structural durability and service life. This study investigates the effect of surface treatment of wood of the invasive tree species of tree-of-heaven, through short-term immersion in an acrylic polymer (Paraloid-B72) containing silica dioxide (SiO₂) nanoparticles at low concentrations (0-4% w/v) to impart hydrophobic behavior and weathering resistance. FTIR analysis confirmed the successful incorporation of the acrylic polymer and silica nanoparticles within the wood structure without altering the chemical integrity of the substrate. For both treated and untreated wood specimens, the physical properties (density, equilibrium moisture content, surface roughness, color-parameters), hygroscopic properties (swelling/absorption, contact angle) and weathering resistance tests were conducted using xenon-arc combined with wetting-drying cycles. The findings revealed that treated wood has significantly improved hydrophobic performance and dimensional stability, reducing moisture uptake. Treatment significantly increased the samples' resistance to artificial weathering, with the effectiveness dependent on nanoparticle concentration. Although moderate surface color changes were observed in treated samples (compared to untreated ones), during their exposure to weathering, reduced lightness and slight increases in red and yellow chromatic coordinates were observed, with treated specimens exhibiting higher color stability during aging. Nevertheless, surface roughness increased significantly by the treatment, slightly restricting the method when a highly smooth surface touch is required. The proposed modification method appears promising to prolong the wooden structures' service-life, meanwhile inspiring modern strategies for conserving historical timber structures that cannot be moved and should be protected by applying less invasive protective methods.