Accelerated degradation of water borne acrylic nanocomposites used in outdoor protective coatings

In this study, the degradation of a water-borne acrylic coating and the influence of rutile-TiO2 (R-TiO2) nanoparticles and a hindered amine light stabilizer (HALS) on its photo-stability in accelerated aging environment has been quantitatively studied by monitoring the chemical modifications occurring upon aging conditions. By using non-destructive analytical methods, like IR and UV-visible spectroscopy, 3D laser microscopy, SEM observations and weight loss measurements, it was possible to follow continuously the formation of photo-oxidative products and the loss of the binder functional groups on a sample undergoing accelerated aging. For the first time, numerous dark spots, randomly dispersed on the whole surface of the sample upon UV/condensation exposure are successfully observed and explained by using a novel technique 3D laser microscopy. Our findings also confirm that HALS greatly improved photo stability to the coating thank to its free radical and hydrogen peroxide scavenging capacity. This work provides some useful information for a better understanding of the degradation behavior of water-borne acrylic coating under accelerated aging conditions. (C) 2016 Elsevier Ltd. All rights reserved.