Slow and rapid thermal decomposition characteristics of enhanced blast explosives for burning in fuel-rich, oxygen-rich conditions

Highlights: • Thermal decomposition kinetics are provided for enhanced blast explosives. • Three explosives are specifically designed for understanding the role of Al and AP. • Simulations of slow and fast cook-off tests are validated against experiments. -- Abstract: The thermal decomposition of metalized polymer-bonded explosives (PBXs) with the addition of ammonium perchlorate (AP) was characterized using slow and fast cook-off simulations, differential scanning calorimetry (DSC), and an isoconversional technique. PBXs #1, #2, and #3 contain 95% cyclotetramethylene-tetranitramine (HMX) with binder; 66% HMX and 25% aluminum with binder; and 25% cyclotrimethylene-trinitramine (RDX), 35% aluminum (Al), 25% AP, and binder, respectively. The roles of Al and AP during thermal decomposition, distinct from the shock-to-detonation transition, were confirmed, indicating that Al does not contribute to the exothermic ignition process due to its higher reaction temperature compared to HMX; instead, Al leads to a higher explosion time and temperature for PBX #2 compared to PBX #1. We extracted the kinetic scheme of PBXs based on the isoconversional technique. In the slow cook-off test for PBX #3, a thermal runaway occurred at the RDX reaction temperature, which is lower than the AP reaction temperature, indicating that AP has a negligible effect. In the fast cook-off test, however, the reactions of RDX and AP occurred simultaneously due to the higher heating rate, demonstrating the influence of AP on the explosion time and temperature.