Thermal decomposition mechanism of HMX/HTPB hybrid explosives studied by reactive molecular dynamics

• Published in: Journal of molecular modeling Vol. 30; no. 7; p. 224
• Main Authors: Chen, Fang, Li, Tianhao, Zhao, Linxiu, Guo, Guoqi, Dong, Ling, Mi, Fangqi, Jia, Xiangyu, Ning, Ruixing, Wang, Jianlong, Cao, Duanlin
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.07.2024; Springer Nature B.V
• Subjects: Activation energy; Characterization and Evaluation of Materials; Chemical reactions; Chemistry; Chemistry and Materials Science; Computer Appl. in Life Sciences; Computer Applications in Chemistry; Decomposition; Decomposition reactions; Dehydrogenation; Disintegration; Explosives; HMX; Hybrid systems; Molecular dynamics; Molecular Medicine; Original Paper; Radicals; Theoretical and Computational Chemistry; Thermal decomposition; Hybrid explosive; HMX; ReaxFF MD; Thermal decomposition; HTPB
• ISSN: 1610-2940; 0948-5023; 0948-5023
• DOI: 10.1007/s00894-024-06022-y

Context The thermal decomposition process of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine/hydroxyl-terminated polybutadiene (HMX/HTPB) hybrid explosives and pure HMX explosives at different temperatures (2000 ~ 3500 K) was investigated using the reactive molecular dynamics method. This study aimed to analyze the effect of binders on the thermal decomposition of HMX at the atomic scale and reveal the thermal decomposition mechanism of HMX/HTPB. The results showed that the thermal decomposition process of the HMX molecule in the HMX/HTPB hybrid system involves a continuous denitration followed by the disintegration of the main ring. The HTPB chain will experience dehydrogenation, dehydroxylation, and chain fragmentation. Including HTPB in the hybrid system significantly increased the presence of H and OH radicals. These radicals then interacted with HMX and its decomposition products and produced more of the final products H 2 O and H 2 in the HMX/HTPB hybrid system compared to pure HMX. Additionally, it was observed that the HTPB chain fragments attached to the HMX decomposition products prevented the formation of N 2 and CO 2 . Furthermore, the activation energies ( Ea ) of the initial and intermediate decomposition stages of the HMX/HTPB hybrid system were 98.45 kJ mol −1 and 90.69 kJ mol −1 , respectively. The results showed that the activation energies of the HMX/HTPB hybrid system are lower than the pure HMX system in these two stages. Consequently, HTPB will enhance HMX’s thermal decomposition and decreased the system’s insensitivity to heat stimuli. Methods The molecular dynamics simulation of the HMX/HTPB hybrid system was performed using the ReaxFF module in the LAMMPS software, and the ReaxFF/lg force field was used to describe the interatomic interactions as well as the chemical reactions.