Kinetic Modeling of Overlapping Thermal Decomposition of 2,6-Diamino-3,5-dinitropyrazine-1-oxide: Two Consecutive Autocatalytic Reactions and the Thermal Safety Assessment

The practical application of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) highly requires the understanding of its thermal decomposition kinetics and thermal hazard prediction. In this study, by combining nonisothermal analysis and the advanced kinetic-based approach, a kinetic model comprised of two consecutive autocatalytic reactions was successfully identified to describe the complex overlapping thermal decomposition behavior of LLM-105, and the contribution of each step to the overall reaction was revealed. The established kinetic model enables the thermal safety evaluation of LLM-105 under different conditions, and the simulated results indicate that the adiabatic time to maximum rate after 24 h (TD24) and 8 h (TD8) of LLM-105 are 257.47 and 268.14 °C, respectively. In addition, the thermal hazard simulations of LLM-105 under mass storage further demonstrate that the self-accelerating decomposition temperature strongly depends on the storage quality, packaging material, and stacking forms of the explosives.