ReaxFF/lg molecular dynamics study on thermolysis mechanism of NTO/HTPB plastic bonded explosive

XF Yuan and SH Zhang and RJ Gou and Y Huang and H Bai and QJ Guo, COMPUTATIONAL AND THEORETICAL CHEMISTRY, 1215, 113834 (2022).

DOI: 10.1016/j.comptc.2022.113834

3-nitro-1,2,4-triazol-5-one (NTO), a very promising high-energy density energy material, has been extensively used in plastic bonded explosive (PBX). However, the potential mechanism of thermal decomposition of PBX systems composed of NTO and the ordinary binder Hydroxyl-terminated polybutadiene (HTPB) is not yet un-derstood. Therefore, in this paper, the mechanism of thermal decomposition of the NTO/HTPB hybrid system was investigated at five temperatures in the range of 2500-3500 K using a reactive molecular dynamics approach (ReaxFF/lg). The results show that the intermolecular reaction paths of NTO in the hybrid system are still re-actions such as dehydrogenation and denitrification reaction, etc. The incorporation of HTPB introduces a large amount of H and OH into the hybrid system, and these radicals react with NTO and the decomposition products of NTO. For example, A large amount of chemical reaction with HNO2 promote the thermal decomposition of NTO. The number of hydrogen transfer reactions between NTO molecules is all reduced to different degrees in the mixed system. The comparison of the number of products is shown that the content of H2O increases greatly and the curve reaches the peak in a shorter time, and the decomposition reaction rate of the system is faster, while the content of N2 decreases substantially. The changes of clusters at five temperatures were analyzed, and the maximum number of clusters increased with the increase of temperature in a certain temperature range, and the high temperature played a certain degree of inhibition on the formation of clusters. The ratio of the number of H, O and N atoms to C atoms in the clusters at each temperature was O/C > H/C > N/C. In addition, The natural logarithm of pre-exponential factor (ln(A)) of the initial and intermediate decomposition stages of the hybrid system were 24.25 and 28.10, respectively, and the activation energies (Ea) were 68.3786 KJ/mol and 59.6588 KJ/mol, respectively. Comparing the activation energy of NTO- only monoplasmic systems, both were reduced to varying degrees. Therefore, the incorporation of HTPB would contribute to the thermal decomposi-tion of NTO and reduce the insensitivity of the system to thermal stimuli.

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