THERMAL-DECOMPOSITION OF ENERGETIC MATERIALS .53. KINETICS AND MECHANISM OF THERMOLYSIS OF HEXANITROHEXAZAISOWURTZITANE

The kinetics of thermal decomposition of hexanitrohexazaisowurtzitane (HNIW) were measured by the isothermal weight loss (TGA) and absorbance changes in the FTIR spectrum at 1 atm. Below 204-degrees-C, the initial 50% of decomposition follows the power rate expression k(T)(1 - alpha)n with n = 1.2. The activation energy is 36.3 +/- 0.6 kcal/mol and log A of 13.6 s-1 for n = 1. The data do not fit an autocatalytic decomposition model. Thermolysis in the 250-degrees-400-degrees-C range was studied by the fast-heat-and-hold/FTIR technique. N-NO2 homolysis dominates the decomposition rate in the lower temperature range and NO2 is the major gas product. Several later stage decomposition reactions of HNIW are proposed in light of the nature of the gas products, their concentration ratios as a function of temperature, and information on the residue. The NO/NO2 ratio shows that oxidation of the residue by NO2 becomes increasing important at higher temperatures.