## Materials and Methods
### Testing and Characterization  
The morphology and chemical composition of microcapsules were analyzed by Quanta 200 environment scanning electron microscopy (SEM) (FEI Company, Hillsboro, OR, USA) and VERTEX 80V Fourier Transform Infrared (FTIR) spectroscopy (Germany BRUKER Co., Ltd., Karlsruhe, Germany). SEGT-J portable color difference meter (Beijing Times Peak Technology Co., Ltd., Beijing, China) was used to test the color difference of the paint film. L, a and b represent the lightness, red-green, and yellow-blue value of the paint film, respectively. L\({}_{1}\), a\({}_{1}\), b\({}_{1}\), c\({}_{1}\) and H\({}_{1}\) were the chromaticity values of one point on the paint film, while L\({}_{2}\), a\({}_{2}\), b\({}_{2}\), c\({}_{2}\) and H\({}_{2}\) were the chromaticity values of another point. \(\Delta\)L = L\({}_{1}\) - L\({}_{2}\), \(\Delta\)a = a\({}_{1}\) - a\({}_{2}\) and \(\Delta\)b = b\({}_{1}\) - b\({}_{2}\). \(\Delta\)L, \(\Delta\)a and \(\Delta\)b are expressed as brightness difference, red green index difference and yellow blue index difference, respectively [24]. The color difference (\(\Delta\)E) was calculated by Equation (1)  
\[\Delta\mathrm{E}=[(\Delta\mathrm{L})^{2}+(\Delta\mathrm{a})^{2}+(\Delta \mathrm{b})^{2}]^{1/2} \tag{1}\]  
HG268 intelligent gloss meter (Tianjin Shunnuo Instrument Technology Co., Ltd., Tianjin, China) was used to test the gloss of the paint film, and the gloss of the paint film was recorded at the incident angle of 20\({}^{\circ}\), 60\({}^{\circ}\) and 85\({}^{\circ}\)[25]. Pencil hardness tester and 6H-6B pencils (Dongguan Huaguo Precision Instrument Co., Ltd., Dongguan, China) were used to measure the hardness of the paint film. Different types of pencil with hardness from soft to hard were used to scratch the paint film, which were 6B, 5B, 4B, 3B, 2B, B, HB, H, 2H, 3H, 4H, 5H, 6H. The greater the number B, the softer the pencil. The greater the H, the harder the pencil. The pencil was inserted into the instrument, clamped with clamps, and kept level. The pencil tip was placed on the surface of the paint film and pushed forward for 7.0 mm at the speed of 0.5-1.0 mm/s. When the paint film was not damaged, the maximum hardness of the pencil was the hardness of the paint film [26]. The adhesion of the paint film was tested by QFH-HG600 film scratch tester (Shenzhen Yeguan Instrument Equipment Co., Ltd., Shenzhen, China). The blade was perpendicular to the surface of the \begin{table}
\begin{tabular}{c c c c} \hline
**Experiment Number** & **Times of Coated Primer** & **Times of Coated Topcoat** & **Micocapsule Adding Method** \\ \hline
1\# & 2 & 2 & primer addition \\
2\# & 2 & 3 & primer addition \\
3\# & 3 & 2 & primer addition \\
4\# & 3 & 3 & primer addition \\
5\# & 2 & 2 & topcoat addition \\
6\# & 2 & 3 & topcoat addition \\
7\# & 3 & 2 & topcoat addition \\
8\# & 3 & 3 & topcoat addition \\ \hline \end{tabular}
\end{table} 
Table 1: Experimental schedule of coating process of the waterborne acrylic coatings with microcapsules. Figure 1: A schematic of sample 1. \begin{table}
\begin{tabular}{c c c c c} \hline
**Experiment Number** & **Micocapsule Weight (g)** & **Weight of Waterborne Primer (g)** & **Weight of Waterborne Topcoat (g)** & **Weight of Waterborne Coating (g)** \\ \hline
1-4\# & 2.0 & 18.0 & 20.0 & 40.0 \\
5-8\# & 2.0 & 20.0 & 18.0 & 40.0 \\ \hline \end{tabular}
\end{table} 
Table 2: Ingredients of the waterborne acrylic coatings with microcapsules. sample, and the film was cut at a uniform rate under uniform pressure. The 100 of 1 \(\times\) 1 mm grids were drawn on the surface of the sample. All cuts shall be cut to the surface of the substrate. The adhesive tape was firmly adhered to ensure good contact between the paint film and the adhesive tape, and then torn off at 60\({}^{\circ}\) angle. The damage of the paint film was observed with a magnifying glass to determine the adhesion grade of the paint film [27]. The adhesion grades of paint film can be divided into 0, 1, 2, 3, 4 and 5 grades from superior to inferior.