Macrocyclic tetra(azo-) and tetra(azoxyfurazan)s: Comparative study of decomposition and combustion with linear analogs

Abstract Thermal decomposition and combustion of macrocyclic tetra(azofurazan)s, TATF, and tetra(azoxyfurazan)s, TOATF, were studied using a number of complementary experimental techniques, namely thermogravimetry, differential scanning calorimetry, manometry, microthermocouple measurements in a combustion wave. Kinetic studies of polyazo- and azoxyfurazans have demonstrated that macrocycles, TATF and TOATF, have a different mechanism of thermal decomposition than their linear counterparts. While linear azo- and azoxyfurazans have relatively low activation energy (130-143 kJ·mol-1) of thermal decomposition, the activation energies for macrocyclic TATF and TOATF are 202-210 kJ mol-1, which is close to the calculated breaking energy of the C-NN bond. The initial stage of decomposition of these macrocyclics is the monomolecular cleavage of the C-NN bond, while linear azofurazan decomposes according to a concerted mechanism, loss N2 or N2O molecules. It was found that the condensed-phase chemistry determines the combustion mechanism of TOATF. Combustion instability is observed for TATF in the pressure range below 3 MPa. Both macrocyclic TATF and TOATF are relatively fast-burning energetic compounds, with burning rates exceeding the burning rates of the CL-20.