Development of Low-Density Explosive Formulations Based on Ammonium Picrate with Slow Detonation Velocities

Traditional slow detonation velocity (D-v) explosives components, such as Baratol (76% Ba(NO3)(2) and 24% TNT), rely on dilution of a traditional explosive with a dense relatively inert material, while some utilize Ca(NO3)(2), ZnO or BaCO3. However, our applications require solely CHNO-based formulations that exhibit slow D-v near theoretical maximum density. Given a target D-v of 6.5 mm/mu s, ammonium picrate was chosen as a convenient explosive to be diluted with a high binder level (14-20%). Thermal equilibrium calculations were performed to determine the binder level to provide the desired D-v. Two formulations were produced, a molding powder with a polystyrene/dioctyl adipate binder, D-v = 6.45 mm/mu s and a cast-cure using hydroxy-terminated polybutadiene/bis-(2,2-dinitropropyl)acetal-formal/MDI binder, D-v = 6.58 mm/mu s. All formulations showed no sensitivity response or compatibility issues. The cast-cured formulation was chosen for further analysis, and cylinder expansion was performed followed by JWL parameterization. Detonation tests confirmed that cast-cured formulation would initiate and propagate unconfined at thicknesses above 12 mm. The ultimate test configuration of the formulation was a sweeping initiation from PBX 9502, with Proton Radiography (pRad) imagery to demonstrate the leading detonation front in the PBX 9502 and a lagging detonation front in the slower cast-cured formulation, as predicted by simulation.