New thermal decomposition pathway for TATB

Abstract

Understanding the thermal decomposition behavior of TATB (1,3,5-triamino-2,4,6-trinitrobenzene) is a major focus in energetic materials research because of safety issues. Previous research and modelling efforts have suggested benzo-monofurazan condensation producing H2O is the initiating decomposition step. However, early evolving CO2 (m/z 44) along with H2O (m/z 18) evolution have been observed by mass spectrometric monitoring of head-space gases in both constant heating rate and isothermal decomposition studies. The source of the CO2 has not been explained, until now. With the recent successful synthesis of 13C6-TATB (13C incorporated into the benzene ring), the same experiments have been used to show the source of the CO2 is the early breakdown of the TATB ring, not adventitious C from impurities and/or adsorbed CO2. A shift in mass m/z 44 (CO2) to m/z 45 is observed throughout the decomposition process indicating the isotopically labeled 13C ring breakdown occurs at the onset of thermal decomposition along with furazan formation. Partially labeled (N18O2)3-TATB confirms at least some of the oxygen comes from the nitro-groups. This finding has a significant bearing on decomposition computational models for prediction of energy release and deflagration to detonation transitions, with respect to conditions which currently do not recognize this oxidation step.

TATB thermal decomposition: Expanding the molecular profile with cryo‐focused pyrolysis GC‐MS

“…The NO gas may also be acting as a reducing agent as furazans form, with NO gas reacting to reduce nitrogen from NO 2 groups, and NO 2 gas reacting to oxidize amine groups as furazans form. Intramolecular electron transfer may also be driving this redox balance as furazans are formed [33]. Overall, these results suggest an auto-oxidation mechanism driven by NO 2 gas formation is a strong driver of TATB thermal decomposition.…”

“…The thermal decomposition lag may be caused by the kinetic barriers to releasing NO 2 groups [30]. The verification of NO 2 loss in TATB thermal decomposition products along with a weak signal measured with various mass spectrometry and vibrational spectroscopy techniques [10] suggests NO 2 molecule is highly reactive [25,[31][32][33] and may drive a portion of the TATB decomposition, resulting from a series of redox reactions, such as the oxidation of the carbon ring to CO 2 and drive the redox reactions aiding in the formation of furazans. The high reactivity may explain why it is only found in trace levels in the gas phase.…”