## 3 Results and Discussion
### Aging Resistance Test of Water-Based Coating Film with Microcapsules
After aging at 160 \({}^{\circ}\)C, the glossiness of the coating film containing microcapsules declined by 0.4, and that of the coating film without microcapsules declined by 4.7. After UV aging, the glossiness of the coating film containing microcapsules declined by 1.1, and that of coating film without microcapsules declined by 3.0. It can be seen that with the increase of aging time, the glossiness of coating film decreased gradually, and the glossiness of coating film containing microcapsules declined less than that of coating film without microcapsules. This was because after aging for a period of time, microcracks will occur on the surface of the coating film, thus the roughness of the coating film will increase and the gloss will decline. However, the paint film with microcapsules can inhibit the appearance of cracks by the action of microcapsules, so the gloss decreases relatively little [38]. The SEM images of the coating film without microcapsule and the film containing microcapsules before and after aging in three environments are shown in Figures 6-8. Figure 6 shows the electron micrographs of the coating films before and after 120 \({}^{\circ}\)C aging. Figure 7 shows the electron micrographs of the coating films before and after 160 \({}^{\circ}\)C aging. Figure 8 shows the electron microscope images of the coating films before and after UV aging. Before aging, the particles on the surface of the coating film containing microcapsules were obvious, while the surface of the coating film without microcapsules was smooth. After aging at 120 \({}^{\circ}\)C, the coating film without microcapsules was seriously cracked, and the surface of the film containing microcapsules was almost unchanged. After aging at 160 \({}^{\circ}\)C, the surface cracks of the two kinds of coating films were not obvious, but the coating film \begin{table}
\begin{tabular}{c c c} \hline \hline
**Aging Time (h)** & **Coating Film with Microcapsule** & **Coating Film without Microcapsule** \\ \hline
0 & 0 & 0 \\
40 & 1.5 & 2.3 \\
80 & 2.1 & 5.1 \\
120 & 3.3 & 5.6 \\
160 & 3.5 & 5.9 \\
200 & 4.2 & 6.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Chromatic aberration of coating film under UV aging environment. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Aging at 120 \({}^{\circ}\)C** & **Aging at 160 \({}^{\circ}\)C** \\ \hline
**Aging** & **Coating Film with** & **Coating Film without** & **Coating Film with** & **Coating Film without** \\
**Time (h)** & **Microcapsule** & **Microcapsule** & **Microcapsule** & **Microcapsule** \\ \hline
0 & 34.1 & 66.5 & 23.8 & 48.9 \\
8 & 33.7 & 65.6 & 23.8 & 48.4 \\
16 & 33.5 & 65.0 & 23.7 & 47.4 \\
24 & 33.4 & 64.3 & 23.9 & 45.4 \\
32 & 33.3 & 63.9 & 23.5 & 45.3 \\
40 & 33.2 & 63.3 & 23.4 & 44.2 \\ \hline \hline \without microcapsules produced more bubbles after the aging experiment. After aging in an ultraviolet weathering test oven, the coating film without microcapsules produced many bubbles of different sizes, while the coating film containing microcapsules only changed slightly. The microcapsules were added to the coatings with the best coating technology, which made the fracture elongation and toughness of the coating film increase, so that the coating film containing microcapsules was better able to adapt to the changes of environmental factors, thus effectively preventing the occurrence and expansion of cracks [39]. In conclusion, after the aging test, the coating film without microcapsules was obviously damaged in different environments, and the coating films containing microcapsules had better stability and aging resistance. Figures 9 and 10 show infrared spectra of coating films without microcapsules and coating films containing microcapsules before and after aging, respectively. In Figure 10, 1639 cm\({}^{-1}\) was attributed to the stretching vibration of C = O in urea-formaldehyde resin in wall materials [40]. After aging, microcapsules were broken and urea-formaldehyde resin was decomposed, so the peak intensity decreases or even disappears.