Azo-pigments effect on UV degradation of contemporary art pictorial film: A FTIR-NMR combination study

In this study, The behavior of Acrylem AC 33–a waterborne paint binder, chemically a ethyl acrylate-methyl methacrylate copolymer-after an UVB-artificial ageing was evaluated. In particular, it has been investigated its behavior in presence of three different azo-pigments – Pigment Red 9, Pigment Yellow 3 and Pigment Yellow 74-, in order to evaluate the effects of these pigments on photodegradation processes of the medium. For this aim, Fourier Transformed InfraRed, both in Attenuated Reflectance and transmission mode, and Nuclear Magnetic Resonance Spectroscopies were used. Thanks to this multianalytical approach, the chemical variations, both on the surface and on the bulk of the pictorial film, have been assessed and the degradation products of surfactant present in the binder were identified. Furthermore, specific effects of these synthetic organic pigments on the photodegradation of the matrix and its additives were observed. The information obtained from this study can be employed in the characterization of differential ageing phenomena in artworks, especially in case of outdoor exposition as it occurs in street-art conditions.