Recrystallization of cyclotetramethylenetetranitramine (HMX) using gas anti-solvent (GAS) process

[Display omitted] ► We prepared small sized β-HMX particles using GAS process. ► We examine the effect of operating parameters on the characteristics of precipitated HMX particles. ► The solvent type can change the crystal phase and structure. ► Among various parameters, CO 2 addition rate has the biggest influence on the particle size. ► We confirm the small sized HMX particles have improved performance of pyrolysis. A gas anti-solvent process (GAS) was used to recrystallize cyclotetramethylenetetranitramine (HMX). A series of experiments were carried out, changing key operating parameters such as the solvent type, temperature, CO 2 addition rate, initial solute concentration, and agitation rate. It was observed that the crystal structure and the crystal phase of precipitated ultra fine HMX particles depended on the solvent type used in the GAS process. As the effects of each parameter on particle size were variable, small sized HMX particles could be obtained by the GAS process at low temperature, high flow rate of CO 2, low solution concentration, and high agitation rate. DSC analysis showed that small sized particles of HMX were expected to have high performance of pyrolysis due to its low activation energy ( E a ) and large enthalpy change (Δ H) at the decomposition of HMX.