A note on evaluating the photocatalytical activity of anatase TiO2 during photooxidation of acrylic clear wood coatings by FTIR and mechanical characterization

We investigate the influence of TiO2 in the anatase (ATiO2) form on the chemical and mechanical properties of clear wood coatings based on a high Tg/low Tg multiphase acrylic binder dispersion. The photooxidation rates were compared using ATR-FTIR techniques and tension tests. The partial least square regression (PLS-R) used showed to be a suitable method to monitor the chemical changes of the polymeric binder and to investigate the influence of the photocatalyst on the photooxidation behaviour. The results obtained by comparing the relative photooxidation rates of the coating systems with and without ATiO2 showed that ATiO2 led to higher photooxidation rates, especially at the beginning of the exposure cycle. Tension tests proved that samples containing ATiO2 are characterized by a significant change of the elastic behaviour at the initial phase of the Xenon arc exposure. After 150 h of Xenon arc exposure, the change of the Young's modulus, which can be attributed mostly to the high Tg component of the multiphase binder, increased at a higher rate. We conclude that the photooxidation of the acrylic binder was strongly accelerated by ATiO2, whereas the effect of increasing concentration of ATiO2 is limited.