Photo-oxidative Stability of a Series of Red Acrylic Paints

Photo-oxidative stability of a series of most common red acrylic paints has been investigated. The paints in question were carmine, quinacridone scarlet, alizarin crimson, brilliant red, vermilion and cadmium red hue. Structural changes, discoloration and weight loss of paints film subjected to UV irradiation in an accelerated ageing chamber were measured using FT-IR spectroscopy, colorimetry and gravimetric analysis before and after 400, 800 and 1200 hours of irradiation. The results of FT-IR spectroscopy showed that cadmium, quinacridone scarlet, primary magenta and vermilion involved most structural changes, where the reduction of transmission peak at 2900 cm-1 region symmetric stretching of C-H bond was noteworthy. Colorimetric measurements indicated the reduction in the absorption of visible light due to photo-degradation of the pigment structure. Furthermore, alizarin crimson and brilliant red have undergone more weight loss compared to the others, which was a result of rapid formation of VOCs.