HMX surface modification with polymers via sc-CO2 antisolvent process: A way to safe and easy-to-handle energetic materials

Abstract The continuous need for energetic materials with increased performance and improved safety characteristics stimulates synthetic efforts as well as physical modification of existing compounds. The present study reports the fabrication of 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane (HMX)-based composites with common commercial polymers, polymethyl acrylate (PMA), acrylonitrile butadiene styrene rubber (ABS), ethyl cellulose (EC), polylactide (PLA), and polyethylene terephthalate glycol (PETG). To precipitate the polymer on the HMX particles, the supercritical CO2-based anti-solvent method was employed. Surface state studies with various modes of scanning probe microscopy show that the polymers at less than 3 wt% content do not form a continuous layer but precipitate as globular islands. Nevertheless, the coating effectively absorbs the mechanical stress, resulting in a much lower sensitivity to impact and a considerable improvement of the HMX friction sensitivity. Specifically, for HMX@3PMA composite the impact and friction sensitivities are 54 J and 240 N, as compared to 7 J and 150 N for neat HMX. Additionally, the beneficial improvement of flowability is observed for the fabricated composites, and evidenced by small-scale flow cup studies. Importantly, the suggested procedure affords the safe and easy-to-handle energetic material powder containing only 1–3 wt% of the polymer additive.