Thermal Decomposition and Stability of CL-20/TNT Co-crystal

Abstract

2, 4, 6, 8, 10, 12-hexanitro-2, 4, 6, 8, 10, 12-hexaazaisowurtzitane, commonly referred to as CL-20, is among the most potent explosives in existence, but it can't be generally applied due to its extremely high sensitivity. However, it has been found that CL-20 can be passivated by TNT within the co-crystal structure. In the current work, many testing methods such as DSC-TG and Raman spectroscopy, etc., were utilized to study the thermally induced decomposition of the CL-20/TNT co-crystal. Results show that the CL-20/TNT co-crystal can no longer maintain over 90 ℃, but its thermal decomposition process is severely retarded by the co-crystal structure, with a sharp increase in decomposition rate at around 127 °C. The activation energies of the thermal decomposition of the co-crystal below and above 127 ℃ are 141 kJ·mol^-1 and 167 kJ·mol^-1, respectively. In the region from 90°C to 127°C, the intermolecular hydrogen bonds between TNT and CL-20 molecules gradually weaken and break, leading to the decomposition of the CL-20/TNT co-crystal; above 127°C, CL-20 within the co-crystal tends to recrystallize into γ-phase CL-20, accelerating the decomposition of the co-crystal. This study discovered a slow decomposition process preceding the rapid decomposition of the CL-20/TNT co-crystal, re-determined the thermal decomposition products and the decomposition temperature of this explosive, and found that the thermal stability of the co-crystal explosive is influenced by the phase transitions of its components.