Estane-Assisted Preparation of Submicron β-Form HMX Particles through Antisolvent Crystallization

Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) particles were prepared through solvent-antisolvent crystallization at room temperature by using dimethyl sulfoxide and ethanol as a solvent and an antisolvent, respectively. Estane, which has been used as a polymer binder in polymer-bound explosives, was added to retard nucleation and inhibit crystal growth. The particles were characterized using scanning electron microscopy, X-ray diffraction analysis, nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. Owing to the nucleation at a high degree of supersaturation, thermodynamically unstable submicron non-β-form HMX particles were formed initially. Their morphology was changed to β-form; the submicron size was maintained while the particles were entrapped in Estane. Estane was removed by washing with tetrahydrofuran, and the purity of the submicron β-form HMX particles was greater than 99 %.