Patrick R. Bowden

Efficiency of perchlorate consumption in road flares, propellants and explosives

When an explosive detonates or a propellant or flare burns, consumption of the energetic filler should be complete but rarely is, especially in the presence of large amounts of non-combustible materials. Herein we examine three types of perchlorate-containing devices to estimate their potential as sources of contamination in their normal mode of functioning. Road flares, rocket propellants and ammonium nitrate (AN) emulsion explosives are potentially significant anthropogenic sources of perchlorate contamination. This laboratory evaluated perchlorate residue from burning of flares and propellants as well as detonations of ammonium nitrate emulsion explosives. Residual perchlorate in commercial products ranged from 0.094mg perchlorate per gram material (flares) to 0.012mg perchlorate per gram material (AN emulsion explosives). The rocket propellant formulations, prepared in this laboratory, generated 0.014mg of perchlorate residue per gram of material.

Steady-state shock-driven reactions in mixtures of nano-sized aluminum and dilute hydrogen peroxide

ABSTRACT Mixtures of nanoaluminum (nAl) and dilute hydrogen peroxide (HP) were studied to determine their potential to detonate when subjected to explosive shock. Results of explosively driven rate stick experiments revealed steady shock propagation for stoichiometric mixtures of nAl and 10 wt% HP. The critical diameter of this composition is estimated to be between 27.7 and 34.5 mm. Detonation velocities between 3.034 and 3.187 mm/μs were obtained, varying with charge diameter and density. This represents the first measured shock-driven, self-sustained reaction in nAl and dilute HP mixtures.

Development of inert density mock materials for HMX

ABSTRACT Inert surrogates or mocks for high explosives are commonly used in place of the real material for complex experiments or in situations where safety is a concern. Here, several materials were tested as potential mocks for HMX in terms of density, thermal stability, and processability. Selection criteria were developed and a literature search was conducted primarily using the Cambridge Structural Database. Out of over 200 potentially acceptable materials, six were chosen for crystallization experiments and a suite of analytical characterization. Of these six, 5-iodo-2ˊ-deoxyuridine, N,Nˊ-bis(2,3,4,5,6-pentafluorophenyl)oxamide, and 2,3,4,5,6-pentafluorobenzamide all were found to be thermally stable at 150°C, matched HMX density as a pressed pellet, and could be crystallized to appropriate particle sizes. These three materials are considered suitable inert density mocks for HMX and will be the subject of future testing.

Characterization of hypervelocity metal fragments for explosive initiation

The fragment impact response of two plastic-bonded explosive (PBX) formulations was studied using explosively driven aluminum fragments. A generic aluminum-capped detonator generated sub-mm aluminum particles moving at hypersonic velocities. The ability of these fragments to initiate reaction or otherwise damage two PBX materials was assessed using go/no-go experiments at standoff distances of up to 160 mm. Lower density PBX 9407 (RDX-based) was initiable at up to 115 mm, while higher density PBX 9501 (HMX-based) was only initiable at up to 6 mm. Several techniques were used to characterize the size, distribution, and velocity of the particles. Witness plate materials, including copper and polycarbonate, and backlit high speed video were used to characterize the distribution of particles, finding that the aluminum cap did not fragment homogeneously but rather with larger particles in a ring surrounding finer particles. Finally, precise digital holography experiments were conducted to measure the three-dim...

Characterizing the propensity of hypervelocity metal fragments to initiate plastic bonded explosives

The off-normal detonation behavior of two plastic-bonded explosive (PBX) formulations was studied using explosively-driven aluminum fragments created by two types of detonators. A generic aluminum-cupped detonator contained 100 mg of PETN which was sufficient to fragment the aluminum into hundreds of sub-mm particles moving at hypersonic velocity; for comparison, a Teledyne RISI® RP-80 was also tested which generated a more substantial flyer plate of aluminum. Low-density polystyrene foam was used as a witness material with subsequent computed tomography analysis to characterize the distribution of particles post-test. Precise digital in-line holography experiments were conducted in situ to measure three-dimensional shape and size of the fastest-moving fragments as they impacted PBXs. Fragments showed significant variability in size, shape and distribution or clustering. Depending on the shot, single or multiple shock impacts could be imparted to the PBX from the generic detonator fragments, or clusters, ...

Evaluation of the Detonation Performance of Insensitive Explosive Formulations Based on 3,3ʹ Diamino-4,4ʹ-Azoxyfurazan (DAAF) and 3-Nitro-1,2,4-Triazol-5-One (NTO)

ABSTRACT Two energetic materials identified for relatively high energy, but little to no response to impact, spark or friction stimuli are 3-nitro-1,2,4-triazole-5-one (NTO), and 3,3ʹ diamino-4,4ʹ-azoxyfurazan (DAAF). More of an outlier in performance versus sensitivity, DAAF illustrates insensitivity by small-scale sensitivity tests, yet has a failure diameter estimated to be 1.25 mm and a short run length to detonation. Because of this unusual behavior, DAAF is an ideal material to formulate with NTO to obtain tailored shock sensitivity and critical diameter, with detonation velocities and pressures higher than PBX 9502. Here, we present detonation properties of Kel-F® bonded formulations with ratios of 20–70 wt.-% DAAF added to NTO. All formulations were evaluated for detonation velocity, aluminum flyer acceleration at jump-off, and via the cylinder expansion test.

Initiation of Insensitive High Explosives Using Multiple Wave Interactions

Insensitive High Explosives (IHEs) increase safety in many types of uses. However, the safety comes at the cost of performance. Initiation of IHE requires large boosters and powerful detonators as well. Multipoint initiation is being utilized to exploit explosive wave interactions to create overdriven states, greatly facilitating the initiation of IHEs. This concept builds from recent explosive experiments where the minimum spot size for single-point initiation in PBX 9502 was determined. Below this threshold, PBX 9502 could not be initiated. This was then expanded to three initiation points, which were smaller than this threshold. Measurements of the velocity and pressure of the wave interactions were collected using Photon Doppler Velocimetry (PDV). Not only was initiation observed, but the resulting pressures at the double and triple points were found to be above the CJ state for PBX 9502. Based on these results, further tests were conducted to isolate and measure the longevity and pressure of this phenomenon using a series of cutback tests.Insensitive High Explosives (IHEs) increase safety in many types of uses. However, the safety comes at the cost of performance. Initiation of IHE requires large boosters and powerful detonators as well. Multipoint initiation is being utilized to exploit explosive wave interactions to create overdriven states, greatly facilitating the initiation of IHEs. This concept builds from recent explosive experiments where the minimum spot size for single-point initiation in PBX 9502 was determined. Below this threshold, PBX 9502 could not be initiated. This was then expanded to three initiation points, which were smaller than this threshold. Measurements of the velocity and pressure of the wave interactions were collected using Photon Doppler Velocimetry (PDV). Not only was initiation observed, but the resulting pressures at the double and triple points were found to be above the CJ state for PBX 9502. Based on these results, further tests were conducted to isolate and measure the longevity and pressure of this phe...

Energetic salt of trinitrophloroglucinol and melamine

We hope to harness the field of energetic co-crystals for development of insensitive, high-performing explosives. As demonstrated by other groups, co-crystals of energetic materials are diverse in their resultant properties versus the native materials. Herein, we discuss the synthesis, characterization, and testing of an energetic co-crystal of trinitrophloroglucinol (1,3,5-trihydroxy-2,4,6-trinitrobenzene) and melamine. Although melamine is not an energetic material, high nitrogen content and insensitivity can be of benefit in a co-crystal. Currently, trinitrophloroglucinol (TNPG) and melamine have been found to exist as a 1:1 ionic co-crystal. Characterization by NMR, IR, small-scale sensitivity, thermal stability and powder X-ray diffraction have all been used to characterize the individual compounds as well as the co-crystals developed.

Characterization of diacetone diperoxide (DADP)

To date, diacetone diperoxide (DADP) has been significantly less studied than its well-known counterpart, triacetone triperoxide (TATP). Much of this disparity in the literature is due to the harsher conditions/multi-step syntheses required to obtain DADP leading to much lower evidence of frequency of use. Because of this, DADP is often misrepresented as being more dangerous (i.e. more sensitive and less stable) than TATP. This paper discusses the synthesis and characterization (sensitivity, thermal stability, etc.) of DADP with comparisons to other energetic organic peroxides (TATP, HMTD and MEKP) and differences in polymorphism, crystal habit and effects of aging and processing differences are discussed. Additionally, the deflagration-to-detonation transition (DDT) behavior of DADP is discussed with comparison to TATP.To date, diacetone diperoxide (DADP) has been significantly less studied than its well-known counterpart, triacetone triperoxide (TATP). Much of this disparity in the literature is due to the harsher conditions/multi-step syntheses required to obtain DADP leading to much lower evidence of frequency of use. Because of this, DADP is often misrepresented as being more dangerous (i.e. more sensitive and less stable) than TATP. This paper discusses the synthesis and characterization (sensitivity, thermal stability, etc.) of DADP with comparisons to other energetic organic peroxides (TATP, HMTD and MEKP) and differences in polymorphism, crystal habit and effects of aging and processing differences are discussed. Additionally, the deflagration-to-detonation transition (DDT) behavior of DADP is discussed with comparison to TATP.