## 3 Results and Discussion
### Thermal Stability Analysis
#### 3.3.2 Pyrolysis Kinetics Analysis  
The thermal stability of the composites was calculated by Coats-Redfern method. The thermal stability of the composites was analyzed from the mathematical point of view by the apparent activation energies. The Coats-Redfern method is a classical integral method for calculating the single heating rate in pyrolysis kinetics. And when the material consists of one or more irreversible reactions, the pyrolysis kinetic expression is divided into two types [30]. When n = 1,  
\[\ln\Big{[}\frac{1-(1-\alpha)^{1-n}}{T^{2}(1-n)}\Big{]}=\ln\Big{[}\frac{AR}{ \beta E}\Big{(}1-\frac{2 RT}{E}\Big{)}\Big{]}-\frac{E}{RT}. \tag{1}\]  
When n \(\
eq\) 1,  
\[\ln\Big{[}\frac{1-(1-\alpha)^{1-n}}{T^{2}(1-n)}\Big{]}=\ln\Big{[}\frac{AR}{ \beta E}\Big{(}1-\frac{2 RT}{E}\Big{)}\Big{]}-\frac{E}{RT}, \tag{2}\]  
where \(\alpha\) is the decomposition rate, \(T\) is the temperature corresponding to the decomposition rate, \(\beta\) is the heating rate, and \(R\) is the gas constant (8.314 J mol\({}^{-1}\) K\({}^{-1}\)), n is the reaction order. Figure 5 shows the curves obtained by fitting the pyrolysis data by the Coats-Redfern method, where n = 1 and n = 0, respectively, to determine the effect of the value of n on the results. When n = 1, \(\ln\Big{[}-\ln[1-\alpha]/T^{2}\Big{]}\) and \(1/T\) are plotted to produce a straight line with a slope of \(-E/R\). When n = 0, the straight line can be calculated in the same way. The apparent activation energy of different specimens can be calculated as shown in Table 4. The value of \(\alpha\) is based on TG and DTG curve data, followed by the selected mass loss of 0.05, 0.1, 0.2, 0.3, 0.5, 0.6, 0.7. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Samples** & \({}^{\textbf{a}}\)**T\({}_{\textbf{5\%}}\)(\({}^{\textbf{c}}\)**C)** & \({}^{\textbf{b}}\)**T\({}_{\textbf{max}}\)(\({}^{\textbf{c}}\)**C)** & \({}^{\textbf{c}}\)**T\({}_{\textbf{95\%}}\)(\({}^{\textbf{c}}\)**C)** & **Samples** & \({\textbf{T}}_{\textbf{9\%}}\)(\({}^{\textbf{c}}\)**C)** & \({\textbf{T}}_{\textbf{max}}\)(\({}^{\textbf{c}}\)**C)** & \({\textbf{T}}_{\textbf{95\%}}\)(\({}^{\textbf{c}}\)**C)** \\ \hline EP & 256 & 290 & 562 & F5N5 & 251 & 289 & 564 \\ F5 & 257 & 294 & 568 & F5N10 & 252 & 292 & 562 \\ F7 & 241 & 299 & 562 & F7N7 & 256 & 291 & 565 \\ F10 & 240 & 289 & 581 & F10N5 & 246 & 290 & 579 \\ F15 & 253 & 289 & 600 & — & — & — & — \\ \hline \hline \end{tabular}  
* T\({}_{\text{5\%}}\) means the temperature to lose 5% weight; \({}^{\textbf{b}}\) T\({}_{\text{max}}\) means the temperature to maximum mass loss rate;
* T\({}_{\text{95\%}}\)means the temperature to lose 95% weight.  
\end{table} 
Table 3: T\({}_{\text{5\%}}\), T\({}_{\text{max}}\) and T\({}_{\text{95\%}}\) of different samples [26]. As shown in Figure 5, the pyrolysis curve of the material exhibits two slopes, indicating that the pyrolysis process should include two stages. The first stage is mainly pyrolysis of EP. The main chain of the EP group is decomposed into a volatile gas at a relatively low temperature, and the main chain with a high bonding pressure in EP is broken at the higher temperature, resulting in an increase in mass loss, which corresponds to the first peak of DTG in Figure 4b. The second stage is the residual carbon oxide decomposition in the air atmosphere, which is consistent with the study of [PERSON] et al. [30; 31]. CF and CNTs do not participate in the reaction due to their excellent high-temperature resistance characteristics within the temperature range. The apparent activation energy of the pyrolysis of the material in Table 4 shows that the varying tendency of the apparent activation energy of the material is consistent regardless of the value of n, except that the activation energy of n = 0 is smaller. This shows that the value of n does not have much effect on the thermodynamics of the material. When n = 1, the activation energy of EP in the first stage is 101.0 kJ-mol\({}^{-1}\).