Unexpected behavior of commercial artists' acrylic paints under UVA artificial aging

摘要

The study of the behavior of acrylic paints after UV-A (400-300 nm, near UV) artificial exposure was further investigated by extending it to more commercially available artists' acrylic paints. The accelerated aging of eight acrylic-based commercial paints was studied using a combination of analytical techniques including Nuclear Magnetic Resonance (NMR) spectroscopies, Pyrolysis coupled with Gas Chromatography/Mass Spectrometry (Py-GC/MS), Fourier Transform Infrared in ATR mode (FTIR-ATR), Direct Analysis in Real Time coupled to Mass Spectrometry (DART-MS) and microscopic techniques, such as Stereoscopic Microscopy (SM) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDS). All the aging process was characterized and monitored to study the signs of decay. During the aging process a gradual loss of the organic surfactant occurred in all the paints, similar to the results contained in a previous study. Interestingly, two of the studied paints presented an unexpected behavior related to the properties of the acrylic binder. In one of such paints solid-state C-13 Cross Polarization Magic Angle Spinning (C-13 CPMAS) NMR spectroscopy was performed. The results obtained by changing the recycled delay and carrying out variable temperature experiments, suggested a change in the internal mobility of the aged sample that could be attributed to the presence of ionomers.