## 3 Results and Discussion
### Effect of Coating Process on Mechanical Properties  
The results of hardness, adhesion, impact resistance and elongation at break of the paint film prepared by different coating process were shown in Table 5. The hardness grades of No. 1-8# were 2H-3H. There was no significant difference between adding microcapsules in primer and adding in topcoat. The number of primer and topcoat had a slight effect on the hardness, which was mainly due to the uneven distribution of microcapsule particles in the coating process [31]. The adhesion of No. 1-8# paint film was good, which was basically grade 0, except that No. 6# and No. 8# were grade 1. For No. 6 and No. 8, the surface adhesion is slightly reduced, which is due to the excessive coating times after adding microcapsules into the topcoat. The impact resistance of No. 1-8# was basically 100.0 N-cm\({}^{-2}\), while that of No. 3# and No. 8# was slightly higher. From the experimental results of the elongation at break, after the microcapsules were added to the waterborne coatings, the elongation at break was significantly increased. This is because microcapsules are shell-shaped spheres. Under the \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **20\({}^{\circ}\)****Gloss (\%)** & **60\({}^{\circ}\)****Gloss (\%)** & **85\({}^{\circ}\)****Gloss (\%)** \\ \hline No microcapsules & 7.3 \(\pm\) 0.1 & 27.9 \(\pm\) 0.6 & 30.7 \(\pm\) 0.7 \\
1\# & 5.6 \(\pm\) 0.1 & 22.9 \(\pm\) 0.5 & 39.0 \(\pm\) 0.9 \\
2\# & 4.1 \(\pm\) 0.1 & 17.1 \(\pm\) 0.4 & 49.7 \(\pm\) 1.2 \\
3\# & 8.3 \(\pm\) 0.2 & 29.1 \(\pm\) 0.7 & 53.3 \(\pm\) 1.3 \\
4\# & 7.1 \(\pm\) 0.1 & 24.5 \(\pm\) 0.6 & 40.7 \(\pm\) 1.0 \\
5\# & 1.9 \(\pm\) 0 & 7.3 \(\pm\) 0.1 & 22.1 \(\pm\) 0.5 \\
6\# & 2.5 \(\pm\) 0 & 10.0 \(\pm\) 0.2 & 16.1 \(\pm\) 0.4 \\
7\# & 2.8 \(\pm\) 0 & 10.8 \(\pm\) 0.2 & 19.3 \(\pm\) 0.4 \\
8\# & 1.8 \(\pm\) 0 & 7.2 \(\pm\) 0.1 & 21.6 \(\pm\) 0.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Effect of the coating process on the gloss of the paint film with microcapsules. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Sample** & **I\({}_{\textbf{z}}\)** & **z\({}_{\textbf{l}}\)** & **b\({}_{\textbf{l}}\)** & **c\({}_{\textbf{l}}\)** & **H\({}_{\textbf{l}}\)** & **I\({}_{\textbf{z}}\)** & **z\({}_{\textbf{l}}\)** & **b\({}_{\textbf{z}}\)** & **c\({}_{\textbf{l}}\)** & **H\({}_{\textbf{l}}\action of tensile force, the rupture of microcapsules will release healing agents, reduce the occurrence of cracks and significantly improve the toughness of the paint film [32]. There was little difference in elongation at break of the paint film, among which No. 3# and No. 5# had higher elongation at break. The mechanical properties of the paint film prepared by the coating process of \"3 layers of primer, 2 layers of topcoat, microcapsules added in primer\" was better. At this time, the paint film hardness grade was 3H, the adhesion grade was 0, the impact resistance was 110.0 N\(\cdot\)cm\({}^{-2}\), and the elongation at break was 29.7%. The liquid resistance of the paint film prepared by different coating process was tested, shown in Table 6. The color of No. 1-8# had no change and the color difference was very small after the NaCl, ethanol and detergent liquid test. After the red ink test, the color difference increased. However, the color difference of the coatings with the microcapsules added to the primer was smaller than that of the topcoat. The reason for this is that after the microcapsules are added to the primer, the topcoat separates the white particles of the microcapsules from the red ink, so that the color difference does not change significantly. The gloss of No. 1-8# paint film was almost unchanged after the liquid resistance test of NaCl, ethanol, detergent and red ink. The liquid resistance of No. 1-8# paint film to NaCl, ethanol and detergent was grade 1, and there was no mark on the surface of the paint film. The liquid resistance level of red ink was different, ranging from 1 to 3.