## 3 Results
### TGA-DTG Analysis of Modified Mt
For the H-P-Mt, the mass loss of physisorbed water was only 0.2 wt.%, compared with 1.9 wt.% for Mt and 4.2 wt.% for H-Mt, indicating that the H-Mt that was intercalated by the surfactants was much less hydrophilic. In discussing the thermal decomposition of certain modified Mt, the curves, in general, can be divided into four different regions [42]. The first region occurs below 200 \({}^{\circ}\)C, and involved the physisorbed water and gases (N\({}_{2}\) or CO\({}_{2}\)) desorption. The decomposition of the organic species was mainly observed in the interval of 200-600 \({}^{\circ}\)C. The dehydroxylation occurred in the range from 600 to 700 \({}^{\circ}\)C. Finally, the evolution of products associated with organic carbonaceous residues occurred. The thermal behavior of the organic clays in the second region was very significant, in terms of their compatibility with polymers as nanofillers, because organic substances begin to decompose in this temperature range. The H-P-Mt showed three mass loss peaks in the temperature range of 200-600 \({}^{\circ}\)C. The peak at approximately 367 \({}^{\circ}\)C was the decomposition of the physically adsorbed surfactants. The peaks at approximately 444 \({}^{\circ}\)C and 492 \({}^{\circ}\)C were mainly related to the degradation of interlayered adsorbed and intercalated surfactants, respectively [43]. The mass loss of the H-P-Mt in the 200-600 \({}^{\circ}\)C temperature range was 18.8 wt.%, which was similar to the P-Mt (19.0 wt.%). However, the interlayer spacing of the P-Mt was 0.41 nm larger than that of the H-P-Mt. Therefore, it could be concluded that the surfactants in the H-P-Mt exhibited a tighter arrangement compared with the P-Mt. Compared with the P-Mt, the maximum mass loss temperature (\(T_{\text{max}}\), obtained from the DTG curve) for the H-P-Mt increased from 474 to 492 \({}^{\circ}\)C, which provided additional evidence that the surfactants in the H-P-Mt exhibited a tighter arrangement. The H-Si-Mt showed three distinct thermal events in the temperature range of 200-600 \({}^{\circ}\)C that were not observed in the H-Mt, and that corresponded to the decomposition of the silane molecules that were adsorbed onto the surface by hydrogen bonds, intercalation and/or chemical grafting [44]. The peak at 200-350 \({}^{\circ}\)C was due to adsorbed silanes on the external surfaces and/or at broken edges, linked by hydrogen bonds to hydroxyl groups. The mass loss between 350 and 450 \({}^{\circ}\)C corresponded to the intercalated silanes, whereas that between 450 and 600 \({}^{\circ}\)C was due to the grafted molecules on the broken edges and  
Figure 6: (**a**,**c**) TGA and (**b**,**d**) DTG curves of Mt and functionalized Mt samples. surfaces [45]. In addition, the mass loss of the H-Si-Mt, between 200 and 600 \({}^{\circ}\)C, was found to be approximately 11.4 wt.%, which was 8.2 wt.% higher than that of the Si-Mt. This result indicated that a significant increase in the amount of intercalated and/or grafted silane molecules in the H-Si-Mt was obtained, as a result of increasing the available hydroxyl groups during the acid activation. Compared with the Si-Mt, the mass loss of dehydroxylation of the H-Si-Mt was reduced, partly due to the consumption of the hydroxyl groups during the grafting reaction [46]. From the results presented so far, it could be concluded that the acid activation exhibited a beneficial effect on the thermal stability improvement of intercalated surfactants, and the amount of silane molecules grafted onto the surfaces. From Table 3, the mass loss of H-Si-P-Mt, between 200 and 600 \({}^{\circ}\)C, was 17.2 wt.%, which was 5.8 wt.% higher compared to H-Si-Mt and 0.9 wt.% lower compared to Si-P-Mt, indicating that the surfactant had been intercalated into the H-Si-Mt interlayer spacing, but the acid treatment could reduce the amount of intercalated surfactants. This result was in accordance with the XRD results. The two stages of thermal decomposition were observed for the H-Si-P-Mt.