## 4 Conclusions  
In conclusion, we studied the thermal decomposition process of KNO\({}_{3}\), boron and BPN based on TG and DSC test data. The weight change of boron powder caused by chemical reaction occurred above 500 \({}^{\circ}\)C. When the temperature was lower than the peak exothermic temperature of decomposition, no  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample 1** & **Weight Loss Ratio after** & **Weight Loss Ratio after** & **Weight Loss Ratio after** \\  & **60 \({}^{\circ}\)C, 4 h (\%)** & **180 \({}^{\circ}\)C, 2 days (\%)** & **180 \({}^{\circ}\)C, 5 days (\%)** \\ \hline
1\#BPN (15:85) & 0.097 & 0.12 & 0.11 \\
4\#BPN (25:75) & 0.372 & 1.04 & 0.98 \\
5\#BPN (25:75) & 0.095 & 1.19 & 1.59 \\ KNO\({}_{3}\) & 0.0083 & 0.044 & – \\ Boron & 1.549 & 5.26 & – \\ \hline \hline \end{tabular} 1  
\end{table}
Table 6: Weight loss ratios of BPN samples in 180 \({}^{\circ}\)C test.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Component** & **60 \({}^{\circ}\)C, 4 h (\%)** & **180 \({}^{\circ}\)C, 2 days (\%)** & **180 \({}^{\circ}\)C, 5 days (\%)** \\ \hline
1\#BPN (15:85) & KNO\({}_{3}\) (\%) & 85.80 & 85.66 & 85.90 \\  & Boron (\%) & 14.87 & 14.88 & 14.85 \\
4\#BPN (25:75) & KNO\({}_{3}\) (\%) & 73.32 & 73.79 & 74.36 \\  & Boron (\%) & 23.04 & 27.38 & 26.24 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Component variation of BPN samples in 180 \({}^{\circ}\)C test [18].  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Component** & **60 \({}^{\circ}\)C, 4 h (\%)** & **180 \({}^{\circ}\)C, 2 days (\%)** & **180 \({}^{\circ}\)C, 5 days (\%)** \\ \hline
1\#BPN (15:85) & KNO\({}_{3}\) (\%) & 85.80 & 85.66 & 85.90 \\  & Boron (\%) & 14.87 & 14.88 & 14.85 \\
4\#BPN (25:75) & KNO\({}_{3}\) (\%) & 73.32 & 73.79 & 74.36 \\  & Boron (\%) & 23.04 & 27.38 & 26.24 \\ \hline \hline \end{tabular}
\end{table}
Table 8: P-t curve of BPN samples in 180 \({}^{\circ}\)C test [19; 20].  
obvious chemical reaction occurred with KNO\({}_{3}\), and only physical changes (crystal transformation and melting) occurred. Combined with a verification test at 180 \({}^{\circ}\)C for two days, it is concluded that boron and KNO\({}_{3}\) components are stable at 180 \({}^{\circ}\)C. With the increase of boron content, the thermal stability of BPN sample improved, and the best performance was achieved when the ratio was 25:75 (B:KNO\({}_{3}\)).  
BPN samples without binder have the best thermal stability. In the 5 day 180 \({}^{\circ}\)C test, the binder affected the weight loss and p-t curve of BPN. Finally, BPN with fluororubber binder is better than BPN with unsaturated polyester binder.  
Conceptualization, C.L. and N.Y.; methodology, C.L. and Z.L.; formal analysis, N.Y.; data curation, J.H. and N.Z.; writing--original draft preparation, C.L.; writing--review and editing, N.Y. and Y.Y.; visualization, X.H.  
This research was funded by Beijing Space Vehicle General Design Department.  
Thanks for the support from State Key Laboratory of Explosive Science and Technology, [PERSON]'s guidance in the field of thermal analysis, and the funding and experimental support from Beijing Space Vehicle General Design Department.  
The authors declare no conflict of interest.