Process optimization studies were performed for the preparation of the high explosive 3,3′‐diamino‐4,4′‐azoxyfurazan (DAAF). These process studies were pursued to address issues such as problematic waste generation products, particle size, impurities, and manufacturability. This paper describes the original synthesis method and inherent issues. An optimization process was designed to investigate the issues with purity and manufacturability. Particle size effects were addressed by adding a recrystallization step to the synthesis. Ultimately, a complete solution to all observed issues was found with a new synthesis process, which now allows DAAF to be prepared without any impurities, with good particle size and without the need for recrystallization. Importantly, the new synthesis process can be performed in an environmentally friendly manner, with the production of non‐hazardous waste.

We have used ultra-small-angle neutron scattering (USANS) with contrast variation to measure the porosity (voids and binder-filled regions) in a composite high explosive, PBX 9501, formulated with a deuterated binder. Little is known about the microstructure of pressed PBX 9501 parts and thus how it is affected by processing.Here, we explore the effect of varying the pressing intensity on the PBX 9501 microstructure. Disk-shaped samples of PBX 9501 were die-pressed with applied pressures ranging between 10,000 and 29,000 psi at 90°C. Five samples were prepared at each pressure that differed in the fraction of deuterated binder, facilitating variation of the neutron scattering length density contrast (~p) and thus, the resolution of microstructural details. The sample composition was determined by calculation of the Porod Invariant as a function of ~p and compared with compositional estimates obtained from the bulk sample density. Structural modeling of the USANS data, at different levels of contrast, assuming both spherical and cylindrical morphologies, allowed the mean size and size distribution of voids and binder-filled regions to be determined. A decrease in the mean diameter of binder-filled regions was found with increasing pressing intensity, while the mean void diameter showed no significant change.2

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The handling safety characteristics of energetic materials must be measured in order to ensure the safe transport and use of explosives. Drop-weight impact sensitivity measurements are one of the first standardized tests performed for energetics. They utilize a small amount of the explosive sample and a standard weight, which is dropped on the material from various heights to determine its sensitivity. While multiple laboratories have used the impact sensitivity test as an initial screening tool for explosive sensitivity for the past 60 years, variability exists due to the use of different instruments, different methods to determine the initiation, and the scatter commonly associated with less-sensitive explosives. For example, standard explosives such as 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane (HMX) initiate reliably and consistently on the drop-weight impact test, whereas insensitive explosives such as 3,3′-diamino-4,4′-azoxyfurazan (DAAF) exhibit variability in sound levels and the expended material. Herein we investigate the impact sensitivity of DAAF and HMX along with a more detailed investigation of ignition sites using a novel “crush gun” apparatus: a pneumatically powered drop-weight tower with advanced diagnostics, including high-speed visual and infrared cameras. Using this crush gun assembly, the ignition sites in HMX and DAAF were analyzed with respect to the effects of particle size and the presence of a source of grit. The formation of ignition sites was observed in both explosives; however, only HMX showed ignition sites that propagated to a deflagration at lower firing speeds. Finally, the presence of grit particles was shown to increase the occurrence of ignition sites in DAAF at lower firing speeds, though propagation to a full reaction was not observed on the time scale of the test. These results enable a better understanding of how ignition and propagation occurs during the impact testing of DAAF.