Characterization of commercial artists’ acrylic paints and the influence of UV light on aging (original) (raw)

2017, International Journal of Polymer Analysis and Characterization

A large part of Mexican artistic heritage was created with artist's acrylic emulsion paints, so it is crucial to investigate their composition, behavior and decay. Acrylic films are complex chemical systems combining organic and inorganic compounds; therefore, the degradation studies require a variety of techniques. We characterize three acrylic films before and after UV ageing. The relative composition of the polymer matrix was studied by nuclear magnetic resonance (NMR), pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and mass spectrometry with direct analysis in real time (DART-MS).The inorganic compounds and surfaces were characterized by microscopic techniques, such as digital microscopy (DM), scanning electron microscopy (SEM),energy dispersive X-ray spectroscopy (EDS) and micro X-Ray diffraction (-XRD).The combined use of these techniques proved to be effective for an in-depth study of the acrylic painting degradation process. The main results were the gradual degradation for the organic surfactant and the loss of inorganic aggregates (talc and carbonates), that led to the Extensive studies on the identification and characterization of these emulsions have been carried out. [3,4,5,6] The two main analytical techniques used were FTIR [7] and Py-GC-MS. [ Error! Bookmark not defined. ] Other less commonly used techniques are the direct thermally-resolved mass spectroscopy (DTMS) [8] and NMR, [ Error! Bookmark not defined. ] the last being ideal for the identification of organic molecules in such paint materials. The surfactants are generally present in low concentrations and they can be either anionic(e.g., sodium lauryl sulfate), cationic(usually based on quaternary ammonium compounds), or nonionic (e.g., alkyl phenol ethoxylates). Non-ionic surfactants, especially those based on polyethoxylates, have been studied in recent years, primarily by their migration to the film surface causing changes in gloss and surface roughness. [9] The main analytical techniques for their study are MS-based techniques, [10,11] several FTIR-based techniques [9,12] and Py-GC/MS. [ Error! Bookmark not defined. ] Many of the artworks with pigmented acrylic emulsions are in outdoor spaces,where ultraviolet (UV) light has an important effect on their photo-oxidative stability. [13,14,15,16] We present the results of a study of three acrylic films,before and after accelerated ageing,by the combined use of techniques: NMR,Py-GC-MS,DART-MS,DM, SEM-EDSand-XRD. EXPERIMENTAL Chemicals / Materials Two of the most used colors in Mexico artworks were chosen: the Toluidine Redand the Hansa Yellow (Politec, Mexico), as well as the unpigmented acrylic binderlike Primal® AC33, (Santiago arte conservación y restauración, Mexico).