## 3 Results and Discussion
### Influence of Coating Processes on the Performances of Waterborne Coatings Containing Microcapsules
#### 3.2.4 Analysis of Microstructure and Infrared Spectrum of Coatings  
The optical property, mechanical property, and liquid resistance tests showed that the coating fabricated by the coating processes of three times of primer and two times of finish, microcapsule added into the primer, which was sample 6, had good performance. The roughness of the coating prepared by \"three times of primer and two times of finish, no microcapsules\" is 0.644 \(\upmu\)m. The roughness of coating with 6.0% microcapsules in the primer (sample No. 6) is 0.936 \(\upmu\)m. The SEM images of these two coatings are compared in Figure 4. It indicates that under the same coating process conditions, which are three times of primer and two times of finish, the waterborne coating without microcapsules is smoother than the waterborne coating with microcapsules in the primer. However, the surface of the coating coated with two times of finish after the three times of primer containing microcapsules is also relatively smooth and has less particles. As shown in Figure 5, it can be observed that for the coating with the microcapsules added into the primer by the method of three times of primer and two times of finish, the characteristic absorption peaks of methyl and methylene are at 2943 cm\({}^{-1}\) and 2875 cm\({}^{-1}\), the strong and sharp absorption peak is -OH at 1731 cm\({}^{-1}\), and the characteristic absorption peak of carbon oxygen single bond in ester group is at 1166 cm\({}^{-1}\). Because the microcapsules do not change the chemical composition of the coating, the spectra of the two  
Figure 4: SEM of the coating prepared by coating process on three times of primer and two times of finish: (**A**) without microcapsules and (**B**) with microcapsules in the primer. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Samples (\#)**} & \multicolumn{4}{c}{**Liquid Resistant Grade**} \\ \cline{2-5}  & **NaCl** & **Ethanol** & **Detergent** & **Red Ink** \\ \hline
4 & 1 & 1 & 1 & 3 \\
5 & 1 & 1 & 1 & 3 \\
6 & 1 & 1 & 1 & 2 \\
7 & 1 & 1 & 1 & 2 \\
8 & 1 & 1 & 1 & 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Effect of coating processes on liquid resistant grade of waterborne coating containing microcapsules. coatings are relatively similar. In order to better visualize the change of polymer film with the microcapsules, Figure S1 shows the infrared spectrum of paint film with microcapsules and microcapsules alone. From the above results, when shellac microcapsules coated with melamine/rice husk powder are mixed to the waterborne paint primer, the coating process of \"three times of primer and two times of finish, microcapsule added into the primer\" is better. The aging resistance test results of waterborne coatings without microcapsules and that with 6.0% microcapsule were analyzed. As shown in Figure 6, when the aging time was 8 h-40 h in the oven at 120 \({}^{\circ}\)C, the chromatic aberration of the coating with 6.0% microcapsule increased from 2.77 to 2.94, and that of the coating without microcapsule increased from 3.18 to 5.06. As shown in Figure 7, the chromatic aberration of the coating with 6.0% microcapsules increased from 19.70 to 30.51, and that of the coating without microcapsules increased from 24.06 to 40.07 when the aging time was 8 h-40 h in the oven at 160 \({}^{\circ}\)C. As shown in Figure 8, with the aging time in the UV climate resistance test chamber increased from 40 h to 200 h, the chromatic aberration of the coating with 6.0% microcapsules increased from 3.25 to 6.92, and the chromatic aberration of the coating without microcapsules increased from 5.44 to 10.44. It illustrated that during the aging process, the chromatic aberration of the coating would gradually increase with the aging time. Based on the two different high-temperature aging processes, the chromatic aberration of the coating without microcapsule increases more than that of the coating with microcapsules.