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

Abstract

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%.