## 2 Theoretical Considerations
### Additive Selection
#### 2.2.1 Silane Coupling Agent  
The silane coupling agent used in this study is mainly used for modifying materials and resins or for bonding and has the characteristic of compounding organic and inorganic materials. The structure of the silane coupling agent is characterized by having at least two types of functional groups with different reactivity in one molecule and is divided into a reactive group that chemically bonds with an organic material and a reactive group that chemically bonds with an inorganic material, as shown in Figure 2.  
The silane coupling agent has both organic and inorganic functional groups, so it acts as a crosslinking agent capable of chemical bonding of both organic and inorganic materials; this reaction improves the tensile performance of rubber, synthetic resin, paint, and the adhesive. In particular, it has the property of increasing the bonding strength of  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{**Quality Standard Criteria**} & \multicolumn{1}{c}{**Performance Result**} & \multicolumn{1}{c}{**Quality Standard**} & \multicolumn{1}{c}{
\begin{tabular}{c} **Enhancement** \\ **Compared to Quality** \\ **Standard** \\ \end{tabular} } \\ \hline Tensile Strength & & 0.33 & More than 0.3 & 110\% \\ Tensile Performance (N/mm\({}^{2}\)) & & 1352 & More than 600 & 225\% \\  & Elongation (\%) & 3.21 & More than 2.9 & 111\% \\ Shear Strength (N/mm) & & 73.33 & \(\pm\)3\% compared to & 1.7\% \\ Solidity Ratio (\%) & & (Standard value = 75) & standard & 1.7\% \\ Viscosity (mPa/s) & & 522 & N/A & N/A \\ (LV 3 Spindle 20 rpm, 23 \({}^{\circ}\)C) & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Water-soluble rubber-asphal-based waterproof coating performance and quality standard.  
Figure 2: Sealant coupling agent structure.  
the materials by integrating different materials, such as organic materials and inorganic materials. In addition, the alkoxysilyl group is hydrolyzed by moisture or moisture in the material to be synthesized, and it is called a silanol group (Si-OH). These silanol groups cause a condensation reaction with the inorganic surface and induce Si-O-M bonding by the condensation reaction, as shown in Figure 3.  
In addition, in the case of another reactive group, X, it is possible to chemically combine inorganic substances and organic substances by combining with organic substances, as shown in Figure 4.  
The overall coupling reaction of the silane coupling agent is shown in Figure 5.  
Table 3 below shows the types of silane coupling agents used in Korea.  
Therefore, in this study, '3-Glycidyloxy Propyl Trimethoxy Silane' was used as an additive for water-soluble rubber asphalt coating film.  
In this study, the mixing method of the silane coupling agent was tested by simultaneously adding and mixing the silane coupling agent when mixing the organic resin and the inorganic material (filler), which was mixed through the integral blend additive method. In the method, the silanol group (Si-OH) generated during hydrolysis of the silane coupling agent is combined with an inorganic additive, and the reactor (X) is combined with an organic raw material to improve physical performance.  
Figure 4: Silane coupling agent organic coupling reaction.  
Figure 5: Total coupling reaction of silane coupling agent.  
Figure 3: Silane coupling agent inorganic coupling reaction.