Comparative study of HMX and CL-20

Abstract

This study deals with a well-known monocyclic nitramine HMX and a relatively new polycyclic strained-cage nitramine CL-20. Experimental data on the powder morphology, simultaneous thermal analysis (STA) and burning rate of binary formulations Al/HMX and Al/CL-20 are presented. Kinetic modelling for HMX and CL-20 are considered based on analysis of STA data obtained for low heating rates. The processing of STA data by the Kissinger method was shown to need to be supplemented with the construction of a thermokinetic model. The thermal decomposition of HMX is reliably described by the reaction of the first order with the autocatalysis. Obtained kinetic parameters of the HMX thermal decomposition correlate with literature-known data on kinetics of the lead stage of HMX combustion. Two types of aluminium powder, i.e. micron-sized and ultrafine, are used to investigate the interaction with both nitramines. Thermal analysis revealed the higher Al oxidation ability of the solid compounds produced at CL-20 thermolysis, than that one of HMX. Burning rate experiments show the differences in the combustion parameters between CL-20- and HMX-based formulations, specifically along with the burn rate level increase for CL-20 monopropellant as compared to HMX one, the pressure exponent and effect of the aluminium particle size variation are also distinct. Results are analyzed and compared to available literature data.