## 3 Results and Discussion
### Structure Analysis  
Through the performance test of the water-based topcoat paint film, it can be seen that when the core-wall ratio of microcapsules was 0.67:1, the comprehensive performance of the water-based topcoat paint film was better. The microstructure of the microcapsule with a core-wall ratio of 0.67:1 is shown in Figure 3. The microcapsules seen in the microscopic image were not so obvious, but a small number of round microcapsules can be seen. This is due to the thick powder observed, which causes the microcapsules to be clumped together [28; 29]. It was obvious from the scanning electron microscope images that the  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Core-Wall Ratio**} & \multirow{2}{*}{
\begin{tabular}{c} **Content of** \\ **Microapsules (\%)** \\ \end{tabular} } & \multicolumn{4}{c}{**Liquid Resistance (Level)**} \\ \cline{3-6}  & & **NaCl** & **Ethanol** & **Detergent** & **Red Ink** \\ \hline \multirow{6}{*}{0.42:1} & 0 & 1 & 1 & 1 & 2 \\  & 5.0 & 1 & 1 & 1 & 1 \\  & 10.0 & 1 & 1 & 1 & 1 \\  & 15.0 & 1 & 1 & 1 & 1 \\  & 20.0 & 1 & 1 & 1 & 3 \\  & 25.0 & 1 & 3 & 1 & 2 \\  & 0 & 1 & 1 & 1 & 2 \\  & 5.0 & 1 & 1 & 1 & 1 \\  & 10.0 & 1 & 1 & 1 & 1 \\
0.50:1 & 15.0 & 1 & 1 & 1 & 2 \\  & 20.0 & 1 & 1 & 1 & 2 \\  & 20.0 & 1 & 1 & 1 & 3 \\  & 25.0 & 1 & 1 & 1 & 3 \\  & 0 & 1 & 1 & 1 & 2 \\  & 5.0 & 1 & 1 & 1 & 1 \\
0.58:1 & 10.0 & 1 & 1 & 1 & 1 \\  & 15.0 & 1 & 1 & 1 & 1 \\  & 20.0 & 1 & 1 & 1 & 2 \\  & 25.0 & 1 & 1 & 1 & 2 \\  & 0 & 1 & 1 & 1 & 2 \\  & 5.0 & 1 & 1 & 1 & 1 \\
0.67:1 & 10.0 & 1 & 1 & 1 & 1 \\  & 15.0 & 1 & 1 & 1 & 1 \\  & 20.0 & 1 & 1 & 1 & 1 \\  & 25.0 & 1 & 1 & 1 & 2 \\  & 5.0 & 1 & 1 & 1 & 1 \\
0.83:1 & 15.0 & 1 & 2 & 1 & 3 \\  & 20.0 & 1 & 3 & 1 & 3 \\  & 25.0 & 1 & 3 & 1 & 3 \\  & 0 & 1 & 1 & 1 & 2 \\  & 5.0 & 1 & 1 & 1 & 1 \\
0.92:1 & 15.0 & 1 & 1 & 1 & 2 \\  & 20.0 & 1 & 2 & 1 & 2 \\  & 25.0 & 1 & 1 & 1 & 3 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Liquid resistance rating of water-based topcoat paint film.  
number of microcapsules was large, and most of them were spherical. The morphology of microcapsules was good, and the size difference was small.  
The SEM picture of the water-based topcoat paint film with 0.67:1 microcapsules is shown in Figure 4. The surface of the water-based topcoat paint film without microcapsules was smooth and has no grain feeling. The surface of the water-based topcoat paint film with 5.0% and 10.0% microcapsules was uneven due to minor agglomeration in microcapsules. The surface particles of the water-based topcoat paint film with 25.0% microcapsules increased, and the agglomeration was serious. When the content of microcapsules was 0-10.0%, the microstructure of the water-based topcoat paint film was clearly characterized. The self-healing performance of the water-based topcoat paint film with the 0.67:1 microcapsules is shown in Figure 5. First, the surface of the water-based topcoat paint film was scratched and the size of the scratch on the first day was observed. Then, the water-based topcoat paint film was placed for five days, and the size of the same place was observed again. The size of water-based topcoat paint film scratches reduced from 33.23 \(\upmu\)m to 22.85 \(\upmu\)m, and the repair rate was 31.23%. Compared with literature [30], the coating repair rate in this paper was higher than the 21.53% reported in literature. It can be seen that microcapsules have a certain repair effect, but because the scratches were larger, it was impossible to completely repair the cracks.