## 3 Results and Discussion
### Effect of Thermal Modification and Wax Impresation on Swelling of Wood  
Figure 2 shows the tangential and radial swellings after water adsorption and absorption. The tangential and radial swellings of the modified groups were smaller than the control group, and the swellings showed a similar trend in both a tangential and radial direction. There were significant  
Figure 1: _EMC_ and water absorption ratio (\(W\)) of control and modified groups: water adsorption (**a**) and water absorption (**b**). Bars showing different letters indicate significant difference (\(p<0.05\)) according to [PERSON]’s multiple range tests. differences (\(p<0.05\)) in adsorption swelling (Figure 2a) between the control and modified groups, indicating TM and TM + WI can both improve wood dimensional stability. Compared with the control group, the maximum reduction of swelling in the tangential direction was about 18.37%, 40.31%, and 71.94%; while in radial direction it was 15.48%, 48.39%, and 67.10%, for 150 \({}^{\circ}\)C TM, 200 \({}^{\circ}\)C TM, and 150 \({}^{\circ}\)C TM + WI, respectively. The dimensional stability of the wood was largely improved after 200 \({}^{\circ}\)C TM and 150 \({}^{\circ}\)C TM + WI. The swelling of the wood after 150 \({}^{\circ}\)C TM + WI had the smallest value, indicating this had the best dimensional stability. In contrast to the 150 \({}^{\circ}\)C TM group, swellings were decreased maximally by 53.57% and 51.62%, in the tangential and radial direction, respectively, after WI. These results indicate that WI played a key role in the reduction of wood adsorption swelling, and the influence of WI on improving dimensional stability was bigger than TM. Generally, the swelling of the wood in the tangential direction was about two times as great as that in the radial direction. However, the difference of swelling in the tangential and radial direction of the 150 \({}^{\circ}\)C TM + WI group became smaller, and they were almost same (Figure 2a). These suggest the wood swelling property was extremely influenced by wax impregnation, which improved the wood dimensional stability significantly. Similarly to the effects on water adsorption swelling, the absorption swelling of the modified groups reduced significantly (\(p<0.05\)), contrasting with the control group. The absorption swelling presented the same tendency as the adsorption swelling, that the 150 \({}^{\circ}\)C TM + WI group had the lowest swelling, followed by the 200 \({}^{\circ}\)C TM group and the 150 \({}^{\circ}\)C TM group. This indicates that, not only TM, but also WI, increased the absorption dimensional stability of the wood. In contrast to the control group and the 150 \({}^{\circ}\)C TM group, the swelling at 150 \({}^{\circ}\)C TM + WI was significantly decreased after wax impregnation. This indicates that WI had a dominant influence on improving the dimensional stability of the wood. The decreased swelling via WI was mainly attributed to the bulking effect of the long hydrophobic chains of wax [27]. The capacity for water absorption decreased after TM and TM + WI, consequently the deformation resistance of the wood increased. Compared with the water adsorption swelling of the 150 \({}^{\circ}\)C TM+ WI group (Figure 2a), the tangential absorption swelling was seemingly greater than the radial swelling (Figure 2b). However, the difference of absorption swelling between the tangential and radial direction was smaller compared with the control group and TM groups. Effect of Thermal Modification and Wax Impregnation on Bending Strength (MOR) and Bending Stiffness (MOE) of Modified Wood  
Figure 3 shows the MOR and MOE of the control and modified wood. Compared with the control group, the MOR of the 150 \({}^{\circ}\)C/6 h and 200 \({}^{\circ}\)C/6 h TM groups decreased by 12.78% and 33.48%, respectively, indicating that the MOR was influenced significantly (\(p<0.05\)) by TM temperature. This result is consistent with the previous findings [30; 31].