Thermal decomposition mechanisms of LLM-105/HTPB plastic-bonded explosive: ReaxFF-lg molecular dynamics simulations

Thermal decomposition is not only related to the explosive's ignition and detonation performances but also to their sensitivity to the surrounding environment. Based on the molecular dynamics method, the interaction and the thermal decomposition mechanism of plastic-bonded explosives (PBXs) composed by 2,6-diamino-3,5-dinitropyrazine-1-oxidated (LLM-105) and hydroxyl-terminated polybutadiene (HTPB) were investigated using the reactive force field molecular dynamics (ReaxFF-lg MD) simulations at 2000 K-4000 K. The interaction between the explosive and the binder effectively stabilizes the explosive crystal and reduces its sensitivity. The predicted activation energy of LLM-105/HTPB is 39.86 kcal/mol, more than that of the pure LLM-105 (36.57 kcal/mol), which reduces the initial decomposition reaction rate of LLM-105 after adding HTPB binder. Products distribution in thermal decomposition shows that the main initial decomposition mechanisms of LLM-105 include the C-NO2, C-NH2 bonds breaking, nitroso rearranging, NH2 elimination and H atom transferring. The H ions from the HTPB dehydrogenation delay the chemical bond breaking to inhibit the decomposition of LLM-105, and the reversible H transfer reactions provide an energy buffering area to reduce sensitivity.