Thermochemical and energy characteristics di-, tri-, and tetraazide-substituted azines as gas-forming components of solid propellants for ramjet engines

A number of di-, tri-, and tetraazido-substituted azines as potential energetic dispersing components of solid rocket propellants for ramjet engines have been studied. The enthalpy of combustion and the enthalpy of formation of several azides (2,4,6-triazidopyrimidine, 2,4,6-triazidopyridine, 3,4,5-triazidopyridine-2,6-dicarbonitrile and 3,4,5,6-tetraazidopyridine-2-carbonitrile) were experimentally determined. Eleven azides studied were compared with MX in terms of the enthalpy of combustion in oxygen to CO$_2$ and water (in the case of the presence of hydrogen in the component), as well as in terms of the temperature of the products of adiabatic conversion of the studied components due to the high enthalpy of formation in the absence of an external oxidizer and the amount of gases released in this process. It has been found that the enthalpy of combustion of all the investigated azides burned in air is significantly higher than that of HMX, and in seven of the azides studied, the combustion temperature was significantly higher. As regards the gas release volume (24–31 mol/kg), the azides are inferior to HMX (41.9 mol/kg). Based on the combination of properties, the investigated azides can be considered as promising dispersing components of solid propellants for ramjet engines.