A Facile Synthesis of 3,3'-Dinitro-5,5'-diamino-bi-1,2,4-triazole and a Study of Its Thermal Decomposition

3,3’-Dinitro-5,5’-diamino-bi-1,2,4-triazole (DABNT) was synthesized by a facile method and its crystalline density was determined as 1.839 g·cm−3 at 293(2) K by X-ray diffraction. Its thermal decomposition kinetics and mechanism were studied by means of differential scanning calorimetry-thermogravimetry (DCS-TG), in situ thermolysis by rapid-scan Fourier transform infrared spectroscopy (RSFTIR) and simultaneous TG-IR technology. The results showed that the apparent activation energies obtained by the Kissinger, Ozawa and Starink methods were 122.9 kJ·mol−1, 123.2 kJ·mol−1 and 123.5 kJ·mol−1, respectively. The thermodynamic parameters of ΔS≠, ΔH≠ and ΔG≠ were −37.5 J·K−1·mol−1, 118.4 kJ·mol−1 and 138.7 kJ·mol−1, respectively. The decomposition reaction process of DABNT starts with the transformation from a primary amine to a secondary amine and then the loss of one nitro-group from the DABNT structure. Gaseous products, such as N2O and H2O, were detected from decomposition in the range of 50-300 °C. Density functional theory (DFT) calculations were further employed to illustrate the decomposition mechanism. The above-mentioned information on the synthesis and thermal behaviour is quite useful for the scale-up and evaluation of the thermal safety of DABNT.