Photoinduced hydrophilicity and self-cleaning characteristics of silicone-modified soya alkyd/TiO2 nanocomposite coating

Abstract

Nano-TiO2-dispersed polymeric coatings have been extensively studied in recent years owing to their photocatalytic-induced self-cleaning characteristics. However, durability and long-term retention of self-cleaning performance of such coatings remain a challenge for practical applications. In the present work, we report the self-cleaning properties of nano-TiO2/silicone soya alkyd-based coating formulations comprising 0.5–5 wt% of nanofiller as well as conventional additives of rutile TiO2 and BaSO4. The nanocomposites were prepared by an in situ process involving dispersion of nano-TiO2 in soya oil, soya alkyd synthesis by alcoholic process, followed by silicone modification. The coatings prepared from the nanofiller-dispersed resin showed significant UV radiation-induced hydrophilicity and photocatalytic degradation of methylene blue (MB) solution. A coating formulation with 2 wt% of nano-TiO2 loading showed a decrease in water contact angle from 87° to < 10° after 24 h of UV radiation exposure and a 50% decrease in intensity of the 664-nm absorbance peak of MB solution after 8 h of UV irradiation. Further, Fourier transform infrared spectroscopy in reflectance mode (ATR-FTIR) and thermogravimetric analysis (TGA) studies revealed minimal degradation of the host matrix after 500 h of accelerated weathering studies with retention of self-cleaning characteristics. These results imply that silicone-modified alkyd resin can be a suitable host matrix for combining the requisite properties of self-cleaning, organic contaminant degradation, photocatalytic stability, and weathering resistance for sustainable self-cleaning applications.