Thermal decomposition of hexanitrostilbene at low temperatures

The thermal decomposition of hexanitrostilbene (HNS), a well known heat res istant explosive, has been investigated by simultaneous TGA/DTA at heating rates between 0.05 and 40 degreesC min(-1). Depending on the temperature/ti me history, the reaction takes place either in the solid phase or in the li quid phase after melting of the sample. In order to observe the solid phase reaction, experiments with constant heating rates well below 2.5 degreesC min(-1) have to be performed. Therefore, it is impossible to judge the ther mal stability of solid HNS using kinetic models derived from DSC experiment s at heating rates of 10-20 degreesC min(-1), as is the standard procedure. In this work, a formal kinetic model has been developed for the thermal de composition of high bulk density I-INS in its solid phase. The model consis ts of three consecutive reaction steps (1) a three dimensional phase bounda ry reaction, dominantly a sublimation, (2) an autocatalytic decomposition r eaction, and (3) a slow reaction of fractal order, supposedly a high temper ature pyrolysis of primary solid products. The model was used to simulate t he stability of HNS under isothermal conditions at temperatures below 300 d egreesC. (C) 2001 Elsevier Science B.V. All rights reserved.