Superhydrophilicity and durability of fluoropolymer-TiO 2 coatings

Abstract

Abstract Self-cleaning fluoropolymer-TiO2 coatings have been in focus as a promising group of materials for a number of years due to their favorable combination of photo-activated hydrophilicity and chemical resistivity of the Teflon-based material. The technology incorporates photocatalysis, which results in oxidation of organic compounds absorbed to a surface, with its superhydrophilic nature, which hinders further absorption of any non-polar substances. The main practical challenge concerning this subject is optimization of the coatings composition without compromising its stability and durability. The aim of this study was to characterize the superhydrophilicity (SHP) of a fluoropolymer-TiO2 coatings as a function of their composition, namely the amounts of polymer, type of the applied curing agent, and the amounts of the titania particles. The hydrophilicity of the coatings was compared to their surface structure and durability to withstand UV-light exposure. In this study, 24 combinations of coatings were studied with contact angle measurements, Fourier transform infra red spectroscopy (FTIR), and scanning electron microscopy (SEM). The results were analyzed statistically with general linear models (GLM) and multivariate data analysis (MDA). The contact angle measurements have shown that time was the most important variable influencing the surface properties of self-cleaning coatings. In terms of composition, the amount of polymer was of significance. Neither the curing agent, nor the amount of titanium dioxide seemed to have any lasting effect on SHP. The analysis of surface structure indicated that illumination influenced the organic polymer, and at long exposure times it led to the degradation of the polymer. This was confirmed by SEM analysis.