Kinetic Analysis of Overlapping Multistep Thermal Decomposition of 2,6-Diamino-3,5-dinitropyrazine-1-oxide (LLM-105)

Thermal decomposition kinetic behavior of energetic materials is of substantial importance for safety enhancement in manufacturing, usage, and storage. The thermal decomposition kinetic behavior of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) was studied by simultaneous differential scanning calorimetry and thermogravimetric analysis (DSC–TG). The thermal decomposition of LLM-105 is a two-step process in which the overall reaction was deconvoluted into two reaction steps for better analysis through different physical meanings consideration of the kinetic data derived from DSC and TG. Kinetic parameters of the two individual reaction steps were characterized through isoconversional and combined kinetic analysis methods. It was found that the activation energy of the first reaction step was 222.2 ± 0.5 kJ mol–1, whereas that of the second reaction step was 244.5 ± 0.5 kJ mol–1. Both steps mostly obeyed the nucleation and growth models (Avrami–Erofeev (A3)). The validity of the obtained kinetic parameters was tested through the successful reconstruction of the original experimental curves. The nucleation and growth were also confirmed through scanning electronic microscopy observations of the morphology evolution during the LLM-105 decomposition. The obtained kinetic parameters and kinetic models contributed to a comprehensive and in-depth understanding of the thermal decomposition of LLM-105.