## 3 Results and Discussion
### Chemical Composition  
The results of the chemical analyses of the structural components of the cell wall are shown in Table 4. The results of the alpha-cellulose content revealed that CS160 had a higher absolute mean than untreated wood, while for the open-system treatments (OS185 and OS210), it was lower than the untreated wood. Despite this, none of the means differed significantly from untreated wood, which suggests that the thermal modification did not have a significant effect on the alpha-cellulose content. This result reinforces the high thermal stability of this cell wall constituent [33]. The thermal modification had varying effects on hemicellulose content: while CS160 had the lowest mean (8.90%), OS185 did not differ statistically from untreated wood, and OS210 was 3 p.p. lower than untreated but with statistical significance. The coefficient of linear correlation between CML and hemicellulose content was very high, negative, and significant (r = -0.996 *), indicating that the higher the CML, the lower the hemicellulose content. Indeed, the correlation between CML and the structural components of the cell wall was only significant (\(p<0.05\)) for the hemicellulose content. Hemicelluloses are the most fragile components of the cell wall due to their thermal sensitivity [3; 20; 21; 22]. The CS160 treatment showed a higher CML (Figure 5) due to the  
Figure 5: Corrected mass loss (%) per treatment. greater degradation of hemicelluloseoses (Table 4). In contrast, OS185 had a CML close to zero, indicating low thermal degradation, with a non-significant difference in the hemicellulose content compared to the control. These results confirmed what had been forecasted in the previous discussion of the results of CML. Teak wood contains several substances in its vessels, which are solubilized during chemical analyses. In thermal modification, especially, the most volatile extractives tend to disappear or degrade, as pointed out by [PERSON] et al. [21]. However, during the degradation of the structural components of the cell wall, new compounds are formed and can be extracted from the wood. The application of high temperatures degrades the hemicellulose, resulting in the formation of acetic acid, which acts as a catalyst for depolymerization and increases polymer breakdown. This leads to the formation of formaldehyde, furfural, and other aldehydes. In addition, part of the organic material can also be degraded and solubilized, justifying the reduction in the hemicellulose content after thermal modification at 160 CS and 210 OS. There was no statistical difference among the treatments for total lignin and insoluble lignin contents, and, along with the results of alpha-cellulose, this indicates that the mass loss was mainly due to the degradation of hemicelluloseoses. Accordingly, the values (Table 4) of r for CML and insoluble lignin were low and non-significant. Some studies [21; 34] mentioned an apparent increase in the lignin content, meaning that there is no formation of this polymer during the treatment, but a condensation of the lignin structure due to the degradation of other wood components, mainly hemicelluloses. Temperatures above 200 \({}^{\circ}\)C result in greater availability of hemicellulose degradation products, which can contribute to the lignin condensation reaction [34]. Another explanation for this apparent increase in lignin content is a change in the balance of the cell wall mass once these analyses are gravimetric. However, this difference had no significant effect on the results of total lignin content between the tested treatments. On the other hand, there was a significant effect of thermal modification of CS160 on soluble lignin when compared to untreated wood. The CML was high enough to cause a significant reduction in soluble lignin, and, in general, the higher the CML, the lower the content of it (r = \(-\)0.880 ns). However, the content of soluble lignin was too low (ranging from 1.61% to 1.89%) to significantly impact the total amount of lignin.