Shock initiation of a heated ammonium perchlorate-based propellant

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Solid propellants containing ammonium perchlorate (AP), aluminum, and a carboxylterminated polybutadiene binder (CTPB) are known to burn reliably and to be very insensitive to transition to detonation under ambient conditions. In accident scenarios, these propellants may become more shock sensitive when they are subjected to heat and/or multiple impacts. The shock sensitivity of one such propellant, ANB-3066, is determined using embedded manganin pressure gauges at an elevated temperature of 170°C. The measured pressure histories are modeled using the Ignition and Growth reactive flow model of shock initiation and detonation. The experiments clearly show that ANB-3066 is not significantly more shock sensitive at 170°C than it is at ambient temperature. The Ignition and Growth reactive flow calculations indicate that less than 20% of the chemical energy of AP and CTPB reactions is released at input shock pressures as high as 21 GPa. The aluminum component does not reach the high temperatures required for it to react. These results indicate that AP-based solid propellants are still extremely resistant to shock to detonation transition even when heated to temperatures close to the thermal decomposition temperature of the propellant formulation. The shock insensitivity of heated AP-based propellants is hypothesized to be due to the melting of the AP component during shock loading and the relatively low temperatures produced by the weakly exothermic decomposition of AP and binder.