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

• Supercritical anti-solvent method employed to fabricate energetic composites. • Polymers precipitate as globular islands on surface of HMX benchmark explosive. • Impact and friction sensitivity are significantly improved even at 1 wt% of polymer. • Flowability for composites is enhanced compared to pristine HMX powder. 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 CO 2 -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.