## 3 Results and Discussion
### The Formation Mechanism of the Condensed Phase  
The microstructures of the residual chars formed after the combustion of EVA/MH, EVA/MH/PCS, and EVA/MH/PCS/DVB are revealed in Figure 13. There are no differences in the surface char layers of the three composites. The surface char layers are composed of close-packed spherical particles (Figure 13(a1-c1)). The char structures in the cross-sections of the residues show differences. There are many long intersecting cracks in the residues of EVA/MH composites, while there are many vertical upward channels that are convenient for gas release and short parallel cracks in the residues of EVA/MH/PCS and EVA/MH/PCS/DVB (Figure 13(a2-c2)). Thanks to the existence of gas channels, the residual char can be free of violent shocks by the degradation gas, and the continuous surface char layer can be maintained. In addition, the particle shape in the cross-section of the residual char of EVA/MH/PCS/DVB maintains the original platelet shape of MH, which is different from that of EVA/MH and EVA/MH/PCS (Figure 13(a3-c3)), indicating that PCS/DVB covering the MH surface plays a non-negligible role in impeding the solid reaction between the molten EVA and MH. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **EVA/MH** & **EVA/MH/PCS** & **EVA/MH/PCS/DVB** & **EVA/MH/PCS+DVB** \\  & **50/50** & **50/47/3** & **50/47/2/1** & **50/47/2+1** \\ \hline T\({}_{5}\) (\({}^{\circ}\)C) & 325 & 349 & 351 & 349 \\ T\({}_{10}\) (\({}^{\circ}\)C) & 335 & 360 & 362 & 360 \\ T\({}_{50}\) (\({}^{\circ}\)C) & 472 & 484 & 484 & 484 \\ T\({}_{\text{max1}}\) (\({}^{\circ}\)C) & 336 & 365 & 369 & 366 \\ T\({}_{\text{max2}}\) (\({}^{\circ}\)C) & 467 & 479 & 485 & 476 \\ R\({}_{\text{max1}}\) (\({}^{\circ}\)C/min) & \(-0.93\) & \(-0.74\) & \(-0.93\) & \(-0.95\) \\ R\({}_{\text{max2}}\) (\({}^{\circ}\)C/min) & \(-1.96\) & \(-2.95\) & \(-1.31\) & \(-1.43\) \\ Residue\({}_{600}\) (\%) & 35.1 & 35.9 & 36.4 & 35.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: TG and DTG parameters of the composites. Figure 13: The microstructures of carbon residues after combustion of composites: (**a**) EVA/MH, (**b**) EVA/MH/PCS, and (**c**) EVA/MH/PCS/DVB. Image 1 is the surface, and images 2 and 3 are cross-sections. Figure 14 shows the XRD diffraction patterns and the FTIR spectra of the residual char of the composites after combustion. The residual char was composed of magnesium oxide, as evidenced in Figure 14 a. However, except for the absorption peaks of the Mg-O stretching vibration at 536 cm\({}^{-1}\) in the FTIR curves, there was a stretching vibration of carbonates at 1431 cm\({}^{-1}\) in the EVA/MH residue, as well as Si-O stretching vibrations at 1100 cm\({}^{-1}\) in the residues of the rest of the EVA composites, which indicates that an amorphous inorganic-phase substance existed in the residues. XPS was adopted to further reveal the binding states of the elements in the residues of EVA/MH and EVA/MH/PCS/DVB. The XPS spectra are given in Figure 15, and the contents of the elements are given in Table 7. For the residue of EVA/MH, the binding states of C1s (Figure 15(b1)) at 286.3 eV and 289.8 eV were attributed to C-O [40] and C=O [41], respectively. The binding states of O1s (Figure 15(b2)) at 531.3 eV and 532.6 eV were attributed to C-O and C=O, respectively, and were probably due to carbonate formed by the oxidation of generated coke and a reaction with magnesium oxide at a high temperature after the decarboxylation of EVA resin [39]. In addition, the element ratio of O to Mg was 2.5:1 (Table 7), far more than the 1:1 ratio in magnesium oxide, indicating the existence and oxidation of coke. Figure 14: The XRD diffraction patterns (**a**) and the FTIR spectra of the residual char (**b**). For the residue of EVA/MH/PCS/DVB, the binding states of C1s (Figure 15(a1)) at 281.7 eV and O1s (Figure 15(a2)) at 531.7 eV were attributed to C-Si and Si-O, respectively, which could be further confirmed by the Si-O (102.4 eV) and Si-C (99.8 eV) of the Si2p binding site (Figure 15(a3)).