3D processing and characterization of acrylonitrile butadiene styrene (ABS) energetic thin films

This study examined processing and characterization of an energetic material synthesized with a binder that is extensively used in existing additive manufacturing methods. Aluminum (Al), molybdenum trioxide (MoO3), and potassium perchlorate (KClO4) are suspended in a solvent–binder system composed of acetone solvent and acrylonitrile butadiene styrene (ABS) binder. The concentration of ABS is varied from 10 to 50 wt% and the mass of acetone is correspondingly varied to ensure a slurry with constant volume percent solids. Three-dimensional films are cast with 1 mm thickness for all ABS concentrations tested. Rheological results show that all slurries exhibit non-Newtonian shear thinning behavior for viscosity as a function of shear rate such that negligible extrudate swell (i.e., die swell) is produced. Investigation into the viscoelastic properties of the slurries revealed them to be highly elastic such that thin sections in the film that cause crack formation can be induced. These results combine to show that 20 wt% ABS is a minimum threshold for ABS to provide a matrix capable of supporting the energetic materials and the elastic nature of the slurry contributes to crack formation below this threshold. Flame speed characterization showed that at and above 40 wt% ABS, the volatiles produced from the thermal degradation of the polymer cause burning above the surface of the film excluding the energetic materials from the reaction. Polymer concentrations of 20 wt% (i.e., 80 wt% energetic material loading) exhibited the highest flame speeds of 1.21 cm/s with an energy density estimated as 5737 kJ/kg. Optimal energetic composites processed using additive manufacturing are achieved if binder concentration can be minimized, as shown here.