Thermal decomposition of energetic materials 50. Kinetics and mechanism of nitrate ester polymers at high heating rates by SMATCH/FTIR spectroscopy

Abstract

Kinetics and mechanism studies of the fast thermal decomposition of 9.45%, 11.7%, and 13.4% N nitrocellulose, poly(vinyl nitrate), poly(glycidyl nitrate) and poly(nitratomethylmethyloxetane) are described by the SMATCH/FTIR technique. Kinetic constants were calculated from the weight loss and temperature traces of thin films heated in the 100°–150°C/s range. The power rate law dα dt = A(1 − α) n exp(− E a RT ) was solved nonisothermally and linearized with n = 2. E a values of 31–34 kcal/mol and log A values of 14.7–16.9 s −1 were obtained. The similarity of the values among the compounds suggests that the same processes control the weight loss in all these compounds. The kinetic constants from SMATCH/FTIR predict the burn rate of the sample when the pressure and temperature conditions are the same. The relatively stable gas products that are detected during the reaction interval indicate that an extensive amount of the decomposition chemistry occurs in the condensed phase. The decomposition reactions at the beginning of the weight loss are similar to those near the end based on the constancy of the relative concentrations.