Isothermal decomposition of HMX before and after thermally induced β-δ crystal transformation

The β-δ crystal transformation of HMX is examined using a self-made constant temperature decomposition gas measuring device, and the isothermal decomposition kinetic parameters of HMX with different crystal phases are obtained. The pressure-time curves of HMX decomposition at different temperatures are divided into two parts, which have their own decomposition mechanism, thereby indicating that phase transition has a significant effect on HMX decomposition. The results of the model-fitting calculation show that the decomposition of β-HMX within the temperature range of 443-466 K conforms to model no. 6, namely, the Jander equation, and the corresponding activation energy is 114.15 kJ mol⁻¹, with ln(A/s⁻¹) = 7.89. The decomposition of δ-HMX within the temperature range of 469-483 K conforms to model no. 26, namely, the Mampel power rule, and the corresponding activation energy is 87.99 kJ mol⁻¹, with ln(A/s⁻¹) = 6.08. The results indicate that the storage life of HMX is 528.23 years at room temperature (298 K) when the reaction depth reaches 0.1%.