Study on thermal decomposition and combustion of insensitive explosive 3,3′-diamino-4,4′-azofurazan (DAAzF)

Thermal decomposition of an explosive with low sensitivity, 3,3'-diamino-4,4'-azofurazan (DAAzF), has been investigated under isothermal conditions at 200-320 degrees C using the thin-walled glass manometer of the compensation type. Changing the ratio of the sample weight to the vessel volume allowed us to measure the kinetic parameters of DAAzF decomposition predominantly in the solid state (k = 5.0 x 10(11) exp(-21,320/T), s(-1)) and the gas phase (k = 3.3 x 10(12) exp(-21,020/T), s(-1)). The kinetics of decomposition in solution (k = 3.5 x 10(6) exp(-14,070/7), s(-1)) have also been measured. Based on the burning rate and thermocouple measurement data, rate constants of DAAzF decomposition in the molten layer at 600-800 degrees C have been derived from a condensed-phase combustion model (k =4.6 x 10(8) exp(-16,680/n s(-1)), which is in a good agreement with kinetic data obtained in the solution at 235-260 degrees C. The mechanism of DAAzF thermolysis and combustion includes initial rupture of C-N bond between the azo-group and furazan ring with subsequent nitrogen evolution and decomposition of the heterocyclic ring. In the combustion wave, the heat release from decomposition of the stable furazan ring follows the heat release from azo-group decomposition, resulting in a distinct two-stage flame structure. (C) 2008 Elsevier B.V. All rights reserved.