## 3 Results and Discussion
### Before Aging: Paints Characterization
#### 3.2.3 Acrylic-Based Samples  
According to the commercial datasheet, the acrylic emulsion used to prepare the samples (Acr_V) was a copolymer of \(n\)-butyl acrylate (\(n\)BA) and methyl methacrylate (MMA). In Supplementary Figure S5 and Table S6, it is possible to identify the presence of the \(n\)BA-MMA copolymer by the IR bands related to the _stretching_ of the C-H bond (2956-2872 cm\({}^{-1}\)); the _stretching_ of the carbonyl group (1727 cm\({}^{-1}\)); and the additional bands at 1436, 1164, and 842 cm\({}^{-1}\), corresponding to the C-H _bending_, the C-O _stretching_, and the C-H _rocking_, respectively [22]. Furthermore, the spectral signal of a surfactant, namely PEO (polyethylene oxide), was identified by the characteristic bands at 1341 and 1114 cm\({}^{-1}\) of the CH\({}_{2}\)_nugging_ and the C-O-C _stretching_[22; 53; 54; 55]. PEO is a non-ionic surfactant that is usually added to stabilize acrylic emulsion [54]. \(\mu\)-Raman analysis supported the results obtained with ATR-FTIR spectroscopy, as shown in Figure 5b, where the characteristic bands of the acrylic emulsion are visible. In particular, bands related to the C-H _stretching_ (2939 and 2873 cm\({}^{-1}\)) and the C=O _stretching_ vibration (1733 cm\({}^{-1}\)) are distinguishable [51]. Other bands associated with this binder are those corresponding to the C-H _bending_ (1449 cm\({}^{-1}\)), the C-H _twisting/rocking_ (1296 cm\({}^{-1}\)), the C-H _rocking_ (844-807 cm\({}^{-1}\)), and the C=O _bending_ (612 cm\({}^{-1}\)) [51]. Py-GC/MS analysis confirmed that the acrylic emulsion used is a copolymer of \(n\)BA/MMA. The TIC (Total Ion Current) pyrogram in Supplementary Figure S6 shows the most intense peaks of MMA at RT 4.23 min and \(n\)BA at RT 6.70 min. Additionally, a peak corresponding to \(n\)-butyl methyl acrylate (\(n\)BMA) at RT 7.71 min was recorded, and peaks related to the pyrolysis products of butyl acrylate were detected as 1-butene, \(n\)-butyl acetate, and \(n\)-butyl tglate. At higher retention time, several peaks were detected, indicating dimeric and trimeric fractions, which are formed due to the depolymerization process occurring during the pyrolysis phase [24; 52]. Specifically, as listed in Supplementary Table S7, it was possible to identify the \(n\)BA-MMA sesquimer and dimer at RT 12.12 min and RT 12.37 min, respectively. Moreover, the \(n\)BA sesquimer, dimer, and trimer were detected. Finally, the _n_BA-_n_BA trimers are present at RT 17.21 min, RT 17.39 min, and RT 18.16 min. Py-GC/MS analysis revealed no additives other than PEO, which was identified only by IR analysis. This may be due to the use of high temperatures in the Py-GC/MS analysis. With ATR-FTIR analysis, it is possible to distinguish the functional groups belonging to the acrylate part and the phenyl group in the styrene-acrylic emulsion samples (Supplementary Figure S7 and Table S8). The acrylate fraction is characterized by the _stretching_ of the C-H bond at 2957, 2931, and 2872 cm\({}^{-1}\); the _stretching_ of the C=O bond at 1728 cm\({}^{-1}\); and the _stretching_ of the C-O bond at 1163 cm\({}^{-1}\)[22; 24]. On the other hand, the bands ascribable to the C-H _stretching_ (3082-3061-3028 cm\({}^{-1}\)), the C=C _stretching_ (1602 cm\({}^{-1}\)), the C-C _vibration_ (1494-1450 cm\({}^{-1}\)), and the C-H _bending_ (758-698 cm\({}^{-1}\)) are characteristic of the phenyl group [22; 24]. As can be observed in Figure 5b, the main styrene-acrylic emulsion bands can be found also in the Raman spectrum. The styrene-acrylic copolymer is characterized by the C-H _stretching_ at 2916 and 2879 cm\({}^{-1}\), and C=O _stretching_ at 1735 cm\({}^{-1}\)[51; 56]. Furthermore, additional bands at 1602, 1449, and 1002 cm\({}^{-1}\), attributable to C=C _stretching_ and C-C _vibrations_, are also present [51; 56]. Py-GC/MS analysis provides more detailed information on the organic fraction.