Thermal decomposition behavior and safety assessment of Diazidoglyoxime (DAzG) synthesis for TKX-50 production: A calorimetric and risk classification study

Diazidoglyoxime (DAzG), a pivotal intermediate in the synthesis of dihydroxylammonium 5,5′-bis-tetrazole-1,1′-diolate (TKX-50)—a high-energy-density explosive with growing applications in defense and aerospace—was comprehensively investigated to elucidate its thermal decomposition behavior and assess safety risks during synthesis. Differential scanning calorimetry (DSC) analyses were conducted on both the precursor dichloroglyoxime (DCG) and product diazidoglyoxime (DAzG), revealing distinct thermal degradation profiles. The onset decomposition temperatures were determined to be 197.8 °C for DCG and 156.9 °C for DAzG, highlighting DAzG’s lower thermal stability. Reaction calorimetry (RC1) studies under varied synthesis conditions further quantified the thermal dynamics of the azidation step, identifying a maximum temperature of the synthesis reaction (MTSR) of 4.9 °C. To evaluate secondary decomposition hazards, accelerating rate calorimetry (ARC) was employed, measuring a TD24 (the temperature at which the time-to-maximum rate under adiabatic conditions, TMRad, reaches 24 h) of 20.4 °C for the reaction residue. This low TD24 value indicates a high propensity for thermal runaway at near-ambient temperatures, necessitating stringent thermal control protocols. Based on Francis Stoessel’s thermal risk classification framework, the thermal risk of DAzG is classified as class 2, signifying moderate but manageable thermal risks during synthesis and handling. The findings emphasize the critical need for real-time temperature monitoring, controlled cooling systems, and hazard mitigation strategies in industrial-scale DAzG production. This study not only advances the understanding of DAzG’s thermal behavior but also provides actionable guidelines for enhancing safety in the manufacturing of advanced energetic materials like TKX-50.