Comparative study on thermal behavior of three highly thermostable energetic materials: z-TACOT, PYX, and TNBP

The thermal behavior, decomposition kinetics and mechanisms of three heat-resistant explosives (HREs), 1,3,7,9-tetranitrodibenzo-1,3a,4,6a-tetraazapentalen (z-TACOT), 2,6-bis(picrylamino)-3,5-dinitropyridine (PYX), and 4,8-di(2,4,6-trinitrophenyl)bisfurazano[3,4-b:3′,4′-e]pyrazine (TNBP) have been investigated by using DSC, TG, FTIR, and TG-MS methods. The crystal structure of TNBP was determined by single crystal X-ray diffraction. Results show that TNBP is more stable than z-TACOT and PYX, while z-TACOT decomposes in two steps with different kinetic parameters. TNBP starts to decompose at around 397.5 °C with a peak temperature of 408.9 °C covered by a heat release of 2710 J g−1 at a heating rate of 5 °C min−1. In contrast, the onset temperature/heat release of z-TACOT and PYX are respectively 391.7 °C/2411 J g−1 and 353.3 °C/1856 J g−1 under the same conditions. Except for the second decomposition step of z-TACOT, all decomposition steps for these compounds are controlled by two or three dimensional nucleation and nucleus growth model (A2 or A3), indicating strong self-heating processes. The major thermolysis products during heating were characterized as CO2, C2H2, N2O, NO, and −C≡N from both FTIR and TG-MS