Rapid ranking of thermal safety realized by accelerating rate calorimetry correlating with small-scale slow cook-off: A case study of four melt-castable explosives

The lack of effective diagnostic tools for thermal safety at the early stage hinders the design of efficient explosives to meet the application demands encountering high-temperature cook-off environments. Thus, exploring the powerful tools for rapid ranking the thermal safety sequence with small dose of explosives is of great importance but remains significant challenges. In this study, we propose a novel method for rapid ranking the thermal safety sequence of explosives via the strong correlations between accelerating rate calorimetry (ARC) tests and small-scale slow cook-off (SSCO) tests. As a proof of concept, this work focuses on clarifying the thermal safety ranking sequence of two typical (TNT, DNAN) and two novel (DFTNAN, DMDNP) melt-castable explosives through multiscale thermal diagnostic tests including TGA-DSC (∼2.0 mg), ARC (∼0.2 g), and SSCO (∼4.0 g). First, the increased thermal stability of DFTNAN, DMDNP, TNT, DNAN can be seen from the rising temperatures obtained by TGA-DSC tests. Second, ten characteristic temperature/pressure parameters at the three important moments (onset, trigger, maximum) of ARC tests have been extracted to correlate with the thermal safety towards SSCO tests. Among the ten parameters, the temperature at trigger moment (Ttrigger) exhibits an increasing trend of DFTNAN (224.3 °C), TNT (256.2 °C), DMDMP (258.8 °C), and DNAN (301.4 °C), which perfectly matches with the improved thermal safety ranking sequence determined by bomb debris, glass debris, and flame propagations of SSCO tests. Additionally, increasing the pressure at trigger moment (Ptrigger) while lowering the pressure increment at sharp exothermic step (ΔPm-t) mainly correlate with the increased thermal safety. Consequently, the combination of six selected characteristic parameters of ARC tests has been successfully optimized to rapidly rank the thermal safety sequence of four melt-castable explosives for the first time, which provides a powerful tool for rapid screening the thermal safety at initial design stage, showing great potentials in energetic materials field.