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The non‐isothermal TG/DTG/DSC technique has been used to study the thermal decomposition of RDX as pure and impure (contain 5 wt. % HMX) in the absence and presence of 5 wt. % irganox 1010 antioxidant under nitrogen atmosphere at different heating rates (4, 6, 8, and 10 °C min−1). The DSC curves show an exothermic peak for decomposition of RDX exactly after its melting point. The activation energy (Ea) for thermal decomposition of pure and impure RDX in the absence and presence of irganox was calculated using non‐isothermal isoconversional methods of KAS, OFW, and Friedman for different conversion fraction (α) values in the range of 0.1–0.9. The pre‐exponential factor (A) and the kinetic model have been determined by means of the compensation effect and the selected model is confirmed by the nonlinear fitting method. The activation energies for thermal decomposition of pure RDX in the absence and presence of irganox are 240.5 to 246.2 and 330.0 to 350.6 kJ mol−1 with the reaction model of R3 and D2, respectively, whereas; the Ea values for decomposition of impure RDX in the absence and presence of antioxidant are 172.1 to 173.0 and 195.3 to 214.2 kJ mol−1, respectively, with the reaction model of R2 for both of them.

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Abstract:The non-isothermal TG/DSC technique has been used to study the kinetic triplet of the thermal decomposition of potassium chlorate at different heating rates (5, 10, 15 and 20 °C·min −1). The DSC results showed two consecutive broad exothermic peaks after melting. The first peak contains a shoulder indicating the presence of at least two processes. The overlapped peaks were resolved by a peak fitting procedure, and the three resolved peaks were used for evaluation of the kinetic triplet for each step. The TG results also showed two consecutive mass losses after melting. The kinetics of the mass loss processes were studied using resolved DTG peaks. The activation energies were calculated using the KAS model-free method. The pre-exponential factor and the best kinetic model for each step were determined by means of the compensation effect, and the selected models were confirmed by the nonlinear model fitting method. The average activation energies obtained from the DSC results were 237.3, 293.8, and 231.3 kJ·mol −1 for the three consecutive steps of thermal decomposition of KClO3. The activation energies were 231.0 and 239.9 kJ·mol −1 for the first and second mass loss steps. The Avrami-Erofeev of Ax/y with the function of g(α) = [−ln(1−α)]x/y (x/y = 5/4 and 3/2) was the most probable model for describing the reaction steps.

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