Ignition experiments and models of a plastic bonded explosive (PBX 9502)

Abstract

Ignition experiments from various sources, including our own laboratory, have been used to develop a simple four-step, pressure-dependent ignition model for PBX 9502, which is composed of 95% by mass triaminotrinitrobenzene (TATB) and a 5% by mass chlorotrifluoroethylene/vinylidine fluoride binder. The four-steps include drying, mono-furazan formation, and decomposition of mono-furazan and TATB into equilibrium products. Our experiments were both sealed and vented and included various ullage percentages ranging from 18% to 75% of unfilled confinement volume. Our sample densities ranged from 38% of the theoretical maximum density (TMD) to 98% TMD. We observed a decrease in ignition times with the higher density samples, an increase in ignition times with increased venting, and an increase in ignition times with increased ullage. From our experiments, we conclude that decomposition of PBX 9502 is pressure dependent, open pore decomposition occurs in low-density experiments, and that closed pore decomposition occurs when the samples are pressed to near full density. In some of our confined high-density experiments we have observed for the first time, multiple temperature excursions prior to ignition caused by internal pressure generation.