UV stability of polymeric binder films used in waterborne facade paints

The UV-stability study of four polymeric binders for water-borne paints, based on acrylic, styrene-acrylic, vinyl acetate and vinyl acetate-butyl acrylate (co)polymers is described. To the best of our knowledge the UV stability of this set of binders relevant to decorative industry is systematically compared for the first time. Thin films obtained from the respective latexes were irradiated with UV light (λ ≥ 275 nm) and analysed using electrokinetic potential (ζ-potential), FTIR ATR spectroscopy, SEM microscopy and differential scanning calorimetry (DSC). The films obtained from different latexes displayed distinct changes in their surface composition and response to UV-irradiation. Among the studied compositions, the vinyl acetate-based ones seem to be the least prone to UV-degradation in the absence of other components typically present in paint formulations. The analytical techniques employed in this study are shown to be complementary and provide information on different regions of the surface layer, depending on their effective probing depth. Especially, a combination of FTIR and ζ-potential measurements is shown useful to clarify the nature of the carbonyl groups formed during photodegradation.