Thermal Decomposition of HMX and RDX: Decomposition Processes and Mechanisms Based on STMBMS and TOF of Velocity-Spectra Measurements

Abstract

A brief history of the decomposition of HMX and RDX is presented to illustrate the development of the mechanisms that are used to explain the decomposition of these two nitramines. The results from simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) and time-of-flight (TOF) velocity-spectra measurements on HMX and RDX are used to identify the decomposition products and to determine their gas formation rates as a function of time during the decomposition of the samples. Both nitramines form H2O, N2O, CH2O, NO, and (CH3)NHCHO during the decomposition. RDX forms NO2 and hydroxy-s-triazine (HST), products associated with N-N bond breaking, whereas HMX forms C2H6N2O, CO, and a nonvolatile residue (NVR). A mononitroso analogue of the parent compound is formed during the decomposition of both materials. The rates of gas formation of the various pyrolysis products along with the macroscopic and microscopic features of the NVR that is generated during the decomposition of HMX suggest that a major process involved in the decomposition of HMX below its melting point is the formation of bubbles containing pyrolysis products within the HMX particles. The pressure of the gas within the bubbles may range up to 35000 psi.