Evaluation of weatherability of latex paint films using synthetic aluminum silicate-modified titanium dioxide photocatalysts as a multifunctional filler

Nanocomposites of TiO₂ modified with semi-crystalline aluminum silicates (AS-T nanocomposites) with various chemical compositions were synthesized using a hydrothermal process and evaluated as fillers for aqueous latex paints. AS-T nanocomposite powders decomposed and mineralized gaseous acetaldehyde more efficiently than a commercial TiO₂-based material. Coating films containing AS-T nanocomposites were prepared using a spray-coating method. The films exhibited high degradation behavior for methylene blue aqueous solution, and the degradation level of one of these films reached up to 80%. After 600 h of accelerated weathering tests, gloss of the reference films decreased to 40% and their surface condition deteriorated, while no change was confirmed in either gloss or the surface condition of AS-Ts-contained films. Furthermore, color difference after the same period showed a value of 8 ΔE* units (CIELAB) for the reference films due to discoloration but relatively favorable values ranging from 3.6 to 5.6 units for AS-Ts-contained films. These results indicate that AS-Ts-contained films possess superior weatherability compared to the reference films. For this film surface designing, appropriate ratios of the surface functional groups with different affinities and proportions of Si(Al)-OH and/or Si-OH-Al in a specific range of chemical compositions should be considered.