## 3 Results and Discussion
### Determination of Surface Wettability and Water Absorption  
The surface CA and water absorption of the modified samples are shown in Figure 11. The CA is a convenient indicator to evaluate the hydrophilic-hydrophobic nature of the surface, and the hydrophobicity of the wood surface is of great significance for practical applications [39; 40; 41]. The CA results showed significant differences between the four treatments (Figure 11b). The CAs of the 103, ZC-103, 120, and ZC-120 treatments after equilibrium were 36.20\({}^{\circ}\), 56.10\({}^{\circ}\), 37.10\({}^{\circ}\), and 47.35\({}^{\circ}\), respectively, indicating that the CA was largest for ZC-103 with ZnCl\({}_{2}\) cured at 103 \({}^{\circ}\)C, 36.65\({}^{\circ}\) larger than in the untreated samples (19.45\({}^{\circ}\)). ZC-120 had the second largest CA, indicating that the addition of ZnCl\({}_{2}\) resulted in an increase in the CA of the wood surface: this was attributed to the proportion of chemicals entering the wood. As shown in Figure 11a, in untreated wood, the deionized water penetrated into the interior of the wood through channels such as pits, and hydrophilic groups such as hydroxyl groups on the surface combined with water molecules to form oxygen bonds and were diffused [41], which resulted in a small CA of the untreated wood and strong hydrophilicity. In contrast, the channels of the modified wood were filled with chemicals, which hindered the infiltration of moisture. The results show that the larger the filling amount, the larger the CA was. In addition, the DM/MA also reacted with hydrophilic groups on the surface of the wood, rendering the surface hydrophobic. However, the unreacted DM monomer also contained two hygroscopic hydroxyl groups, which generated hydrogen with water molecules. The combination of the bonds made the surface of the wood somewhat hydrophilic, but since most of the modifiers underwent polycondensation into macromolecules inside the wood, in general the wood surface was still hydrophobic.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Methods** & \(T_{onset}\) (\({}^{\circ}\)C) & \(T_{max}\) (\({}^{\circ}\)C) & \(T_{end}\) (\({}^{\circ}\)C) & **Residual Mass (\%)** \\ \hline Ctrl & 221.36 & 348.21 & 494.23 & 14.72 \\
103 & 203.68 & 332.42 & 495.49 & 23.25 \\ ZC-103 & 187.80 & 323.96 & 495.34 & 27.65 \\
120 & 210.85 & 337.45 & 495.50 & 19.82 \\ ZC-120 & 205.75 & 325.01 & 495.40 & 26.97 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Thermal properties of the 10% DM + 10% MA-treated samples in different groups. \(T_{onset}\): decomposition onset temperature; \(T_{max}\): maximum decomposition rate temperature; \(T_{end}\): decomposition termination temperature.  
As shown in Figure 11c, the water absorption of the samples was also related to the amount of fixation agent in the wood. The maximum water absorption values of the 103, ZC-103, 120, and ZC-120 treatments were 133.96%, 110.17%, 140.41%, and 139.23%, respectively, and the water absorption in all groups was lower than in the untreated wood. The STDVA of the CA was in the range of 1.40\({}^{\circ}\) to 2.90\({}^{\circ}\), indicating that the left and right CAs and the characteristics of the wood surface were relatively uniform. In addition, the STDVA of water absorption was in the range of 0.16% to 14.15% and increased with increasing water absorption, but both were within the allowable range. In summary, the CA was the largest for the group with ZnCl\({}_{2}\) cured at 103 \({}^{\circ}\)C, which proved that these conditions greatly improved the hydrophobicity of the wood.