The Effect of Pollutant Gases on Surfactant Migration in Acrylic Emulsion Films: A Comparative Study and Preliminary Evaluation of Surface Cleaning

Abstract

From their first employment in the 1950s, acrylic emulsions have remained widely used as art material today. Although under certain deteriorating conditions they are very stable, if exposed to high humidity and atmospheric pollutant gases, their structural and chemical conformation is strongly affected. Dealing with the resulting surfactant migration, various cleaning treatments were considered over the years. However, their choice remains difficult as they easily alter the acrylic component, especially if in contact with aqueous solutions. The present study focuses on investigating the stability of acrylic emulsion films exposed to accelerated aging by various pollutant gases. Firstly, a comparative analytical study was carried out in order to morphologically (by 3D optical and Atomic Force Microscopy) and chemically (by Raman and Infrared spectroscopy) characterize the reactions and degradation products. Subsequently, two water-based cleaning treatments were tested, and a preliminary evaluation of their cleaning effectiveness was performed. The results show that the reaction of atmospheric gas pollutants with water molecules in moisture leads to acidic reaction products that attack the acrylic matrix and favor the migration of the surfactant to the surface. The effectiveness of cleaning treatments depends on the aging conditions applied, which further lead to different surface morphological changes.

Data Fusion Approach to Simultaneously Evaluate the Degradation Process Caused by Ozone and Humidity on Modern Paint Materials

“…It was characterized as nBA/MMA as it shows C-H bond stretching vibrations (at 2956-2875 cm −1 ), C=O stretching (at 1726 cm −1 ), CH 2 -and -CH 3 bending vibrations (1452 and 1386 cm −1 , respectively), and the C-O-C and C-O stretching bands (at 1236, 1160, 1146 cm −1 ) in the fingerprint region [46,59,60]. Furthermore, the spectral signal of a surfactant, namely PEO (polyethylene oxide), was identified by the three characteristic absorbance bands at 2891, 1343, and 1112 cm −1 [61,62].…”

Protecting Street Art from Outdoor Environmental Threats: What Are the Challenges?

“…Furthermore, they can form micelles, resulting in a stabilising effect in paints. The two most studied and identified examples in modern paints are polyethylene glycol (PEG) and polyethylene oxide (PEO) [44,45]. (5) Surface modifying agents.…”

“…In addition, thermal stresses tend to expand and shrink paint layers, inducing the mechanical failure. In drastic outdoor conditions and sunlight exposure, additives (such as surfactants and plasticisers) can migrate towards the surface following the cracks network and then be removed by rain, leading to a more brittle and fragile paint film, devoid of the plasticisers [32,45,50]. Equally, studies described the migration to the surface of the paint layer of inorganic additives of the paint itself or from background layers (as preparatory layers or underlying paints) [52], in particular, it has been observed that thinner paint layers (as the one produced by spray paints) are more susceptible to this phenomenon [50].…”