The effects of TiO₂ particles on the physico-chemical properties of polyester coatings

Titanium dioxide (TiO₂) based surface coatings with appropriate binding matrices provide notable characteristics such as long-lasting efficacy and physico-chemical durability to minimise complex failures in a variety of applications. However, how the crystalline forms of TiO₂ and their distribution within matrices affect the coating characteristics remains unclear. In this research, we prepared TiO₂-based coatings by compositing two forms of TiO₂ nanoparticles (rutile and anatase) with an unsaturated polyester resin (UPR) matrix to produce TiO₂/UPR coatings, followed by physico-chemical characterization. Morphology and topography results revealed that the rutile nanoparticles showed a sphere-like shape, while the anatase nanoparticles had an irregular polyhedron structure. Additionally, a ring-like structure was formed on all coatings whilst coatings containing pure rutile exhibited slight agglomeration in the boundaries of rings. In contrast, anatase-containing coatings presented more agglomerates inside the rings. The consistent phenomenon was demonstrated by Raman and XRD analysis. The addition of anatase in the coatings significantly increased the surface free energy and hardness based on the wettability and nanoindentation tests. The chemical durability evaluation suggested that anatase improved the ability of chemical solution resistance of coatings by strong interaction between nanoparticles and matrix resulting from the irregular polyhedron structure and high surface free energy of the anatase nanoparticles. Excellent anti-wear performance was observed in anatase-containing coatings, implying that the nanoparticle distribution and the resulting higher hardness affected the wear-resistance of the TiO₂-based coatings.