Evaluation of weathering resistance of cross-laminated timber blocks surface-treated with TiO2 nanoparticles by liquid-precursor flame spray pyrolysis

Wood is a versatile and renewable resource utilized in a wide range of applications, including tools, furniture, construction, and advanced engineering structures. However, certain inherent properties of wood, such as moisture and ultraviolet (UV) degradation, impose limitations on its long-term durability and dimensional stability for outdoor applications. This research investigates the weathering durability of cross-laminated timber (CLT) blocks surface-treated with titanium dioxide (TiO2) nanoparticles synthesized via liquid-precursor flame spray pyrolysis (FSP), directly deposited onto the surface of CLT blocks, and thereby resulting in a porous TiO2 coating. This coating endows the CLT surface with superhydrophobic properties evidenced by a water contact angle of ≥150°. Results from scanning electron microscopy and X-ray diffraction show the coating to be comprised of crystalline, sub-100 nm individual and aggregated TiO2 particles with significant porosity. Even after an 8-week accelerated weathering test, a portion of the crystalline TiO2 particles remains on the CLT surface. The TiO2-treated CLT demonstrates enhanced resistance to discoloration and gloss change over 8-weeks of accelerated weathering conditions, which are evidenced by a total color difference (ΔE) that is 3–4 times lower than that of the untreated CLT in the initial two weeks, and 58% lower after 8 weeks of weathering. Furthermore, the TiO2-treated CLT exhibits fewer weathering defects, such as splits and cracks, than the untreated CLT. The enhanced weathering durability of the TiO2-treated CLT is attributed to reduced lignin degradation, which is supported by the Fourier-transform infrared spectroscopy analysis. The findings of this study suggest that the TiO2 coating by FSP offers a viable and cost-effective method for modifying engineered wood products for improving hydrophobicity and protecting against the deteriorating effects of UV irradiation and moisture exposure. •TiO2 nanoparticles are applied to the surface of CLT blocks by flame spray pyrolysis (FSP).•The FSP process on CLT results in a TiO2 layer consisting of sub-100 nm TiO2 nanoparticles on CLT.•TiO2-treated CLT shows enhanced resistance to discoloration and weathering defects during an 8-week accelerated weathering test.•Enhanced protection against lignin degradation is attributed to the UV-absorbing properties of TiO2 nanoparticles.