Energetic Residues from the Detonation of IMX‐104 Insensitive Munitions

The development of insensitive munitions by NATO countries is an ongoing effort. Less‐sensitive ingredients in both explosives and propellants will ensure the protection of deployed troops against an unwanted reaction to an external stimulus on the munitions stockpile. In the US Army, current efforts are directed towards the development of melt cast insensitive explosive formulations. Various formulations, mainly based on DNAN and NTO, have been developed and are now being fielded. Our research goal is to measure the deposition rate of energetics compounds from various insensitive munitions detonation scenarios. Our hypothesis is that the relative insensitiveness of these formulations leads to slightly higher deposition rates than conventional explosive formulations. This paper describes detonation residues research on mortar rounds containing IMX‐104 explosive. Analyses indicate that high‐order detonation residues are slightly greater for this formulation than for conventional munitions. However, blow‐in‐place detonations (BIPs) resulted in much higher residues deposition, indicating that a larger donor charge is required for efficient detonation. The highly soluble compound NTO was particularly problematic, with BIP deposition approaching 95 % of the original load. Toxicological studies of NTO are not finalized, leaving considerable uncertainty regarding the feasibility of approving these rounds for distribution.     

Thermal and Sensitivity Study of Dihydroxyl Ammonium 5,5′‐Bistetrazole‐1,1′‐diolate (TKX‐50)‐based Melt Cast Explosive Formulations

Dihydroxyl ammonium 5,5′‐bistetrazole‐1,1′‐diolate (TKX‐50) is a promising energetic material with predicted performance similar to RDX as well as to CL‐20. In the present study, TKX‐50 was evaluated as a possible replacement for RDX in TNT‐based, aluminized as well as non‐aluminized melt cast formulations. Thermal analysis reveals the compatibility of TKX‐50 with benchmark explosives like RDX and TNT in explosive formulations. This paper describes the thermal and sensitivity study of TKX‐50 with RDX and TNT‐based melt cast explosives. The result indicated that TKX‐50 can be effectively used as a RDX replacement in melt cast explosive formulations. TKX‐50/TNT‐based aluminized composition shows more thermal stability than RDX/TNT based composition, which clearly indicated the usefulness of TKX‐50 in melt cast explosive formulations.     

Laboratory‐Scale Method for Estimating Explosive Performance from Laser‐Induced Shock Waves

A new laboratory‐scale method for predicting explosive performance (e.g., detonation velocity and pressure) based on milligram quantities of material is demonstrated. This technique is based on schlieren imaging of the shock wave generated in air by the formation of a laser‐induced plasma on the surface of an energetic material residue. The shock wave from each laser ablation event is tracked for more than 100 μs using a high‐speed camera. A suite of conventional energetic materials including DNAN, TNT, HNS, TATB, NTO, PETN, RDX, HMX, and CL‐20 was used to develop calibration curves relating the characteristic shock velocity for each energetic material to several detonation parameters. A strong linear correlation between the laser‐induced shock velocity and the measured performance from full‐scale detonation testing has been observed. The Laser‐induced Air Shock from Energetic Materials (LASEM) method was validated using nitrocellulose, FOX‐7, nano‐RDX, three military formulations, and three novel high‐nitrogen explosives currently under development. This method is a potential screening tool for the development of new energetic materials and formulations prior to larger‐scale detonative testing. The main advantages are the small quantity of material required (a few milligrams or less per laser shot), the ease with which hundreds of measurements per day can be obtained, and the ability to estimate explosive performance without detonating the material (reducing cost and safety requirements).     

Characterization of PAX‐21 Insensitive Munition Detonation Residues

Insensitive high explosives are being used in military munitions to counteract unintended detonations during storage and transportation. These formulations contain compounds such as 2,4‐dinitroanisole (DNAN) and 3‐nitro‐1,2,4‐triazol‐5‐one (NTO), which are less sensitive to shock and heat than conventional explosives. We conducted a series of four tests on snow‐covered ice utilizing 60‐mm mortar cartridges filled with 358 g of PAX‐21, a mixture of RDX, DNAN, and ammonium perchlorate. Rounds were detonated high‐ and low‐order using a fuze simulator to initiate detonation. Blow‐in‐place (BIP) operations were conducted on fuzed rounds using an external donor charge or a shaped‐charge initiator. Results indicate that 0.001 % of the original mass of RDX and DNAN were deposited during high‐order detonations, but up to 28 % of the perchlorate remained. For the donor block BIPs, 1 % of the RDX and DNAN remained. Residues masses for these operations were significantly higher than for conventional munitions. Low‐order detonations deposited 10–15 % of their original explosive filler in friable chunks up to 5.2 g in mass. Shaped‐charge BIPs scattered 15 % of the filler and produced chunks up to 15 g. Ammonium perchlorate residue masses were extremely high because of the presence of large AP crystals, up to 400 μm in the recovered particles.     

Ageing of Australian DNAN Based Melt‐Cast Insensitive Explosives

2,4‐Dinitroanisole (DNAN) is a new melt‐cast matrix ingredient that replaces traditional TNT in TNT‐based melt‐cast explosives. Aside from sensitiveness improvements, the use of DNAN allows for the continued operation of existing melt‐cast facilities (for example the Australian Munitions plants located at Mulwala and Benalla) without the need for major plant modifications. Researchers at Defence Science and Technology Group (DST Group) have developed several DNAN based formulations that have been extensively characterized. In an effort to better understand the ageing properties of these formulations, an accelerated ageing program was undertaken. Testing was conducted under two different ageing conditions; the first test condition was conducted at a constant 60 °C with ambient humidity and the second test condition was the A2 diurnal cycle (representative of hot dry climates). Analysis of the formulation density, sensitiveness, mechanical and thermal properties was made at three‐month intervals for a period of 12 months and results compared with conventional explosives similarly aged. For all DNAN‐based formulations there was negligible change in impact, friction, electrostatic discharge, and thermal testing over time. These results highlight the ability of the ARX formulations to diurnal temperature cycling and to hold favorable sensitiveness properties to various stimuli.     

Sensitivity and Detonation Characteristics of Selected Nitramines Bonded by Sylgard Binder

Four plastic explosives based on cyclic nitramines and polymeric matrix were prepared and studied. The nitramines were RDX (1,3,5‐trinitro‐1,3,5‐triazinane), HMX (1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocane), BCHMX (cis‐1,3,4,6‐tetranitro‐octahydroimidazo‐[4,5‐d]imidazole), and ϵ‐CL20 (ϵ‐2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane, ϵ‐HNIW). Sylgard 184 was used in the all PBXs prepared samples as a binder. The sensitivities to different mechanical stimuli were determined. The detonation velocities were experimentally measured. Detonation characteristics were calculated by EXPLO5 thermodynamic code. For comparison, standard plastic explosives, Composition C4, Semtex 10, and EPX‐1 were studied. Results showed that the experimental detonation velocities as well as the calculated detonation parameters decrease in the following order: CL20‐sylgard>HMX‐sylgard≥BCHMX‐sylgard>RDX‐sylgard. Calculations by EXPLO5 computer program resulted in detonation velocities close to the experimental ones with 3.1 % maximum difference. Urizar coefficient for the Sylgard binder was calculated from experimental data. An inverse linear relationship between friction sensitivity and heat of detonation of the studied samples was observed. Sylgard binder significantly decreased the sensitivity of all the studied nitramines. Among these prepared samples, the properties of BCHMX‐sylgard are similar to other ordinary plastic explosives.     

Explosive Strength and Impact Sensitivity of Several PBXs Based on Attractive Cyclic Nitramines

Plastic explosives based on different cyclic nitramines with different polymeric matrices were prepared and studied. The used polymeric matrices were fabricated on the basis of polyisobutylene (PIB), acrylonitrile‐butadiene rubber (ABR), Viton A, and polydimethyl‐siloxane as binders, whereas the nitramines named RDX (1,3,5‐trinitroperhydro‐1,3,5‐triazine), β‐HMX (β‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine), BCHMX (cis‐1,3,4,6‐tetranitrooctahydroimidazo‐[4,5‐d]imidazole) and ε‐HNIW (ε‐2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane) were used as explosive fillers. Commercial Semtex 10, based on pentaerythritol tetranitrate (PETN), was used for comparison. Impact sensitivity, loading density, ρ, detonation velocity, D, and relative explosive strength (RS) measured by ballistic mortar were determined. It was concluded that plastic BCHMX based on Viton A or PIB‐matrix exhibits higher RS compared with PBXs based on RDX and HMX. Correlations between RS and the impact sensitivity, the ρD² term and the square of the detonation velocity were studied and discussed. The results confirm the well‐known fact that increasing the performance is usually accompanied by an increase in the sensitivity of the explosives. In this connection, Viton A enables achieving a high RS, but with a relatively high sensitivity of the PBXs, whereas the polydimethyl‐siloxane matrix should perhaps give PBXs with optimum explosive strength and sensitivity parameters.     

Study of the Effect of Covolumes in BKW Equation of State on Detonation Properties of CHNO Explosives

Due to its simplicity, the Becker‐Kistiakowsky‐Wilson (BKW) equation of state has been used in many thermochemical codes in the calculation of detonation properties. Much work has been done in the calibration of the BKW EOS parameters to achieve agreement with experimental detonation velocities and pressures thus resulting in many different sets of BKW constants (α, β, κ and θ) and covolumes of detonation products, with varying levels of accuracy over broad density limits, i.e. broad pressure limits. The covolumes of the product gases in BKW EOS may be regarded as measures of intermolecular interactions, and their values should affect the predicted detonation properties, particularly at higher explosives densities. This work aims to study the effect of covolumes on calculated values of detonation parameters. Several sets of covolumes available from literature and derived by different methods (matching experimental Hugoniots of individual products, by stochastic optimization, and calculated from van der Waals radii), were studied. In addition, the covolumes of the product gases were also calculated by ab initio methods. The effect of covolumes is studied comparing detonation properties calculated using different sets of covolumes, and experimental data for a series of standard CHNO explosives. It was found that it is possible to reproduce experimental detonation velocities and pressures within reasonable accuracy (root mean square error of less than 5 % for all tested sets) using different set of covolumes, and simultaneously optimizing constants in BKW EOS. However, different values of covolumes strongly affect the composition of detonation products at the Chapman‐Jouguet state. It particularly applies to oxygen‐deficient explosives and at higher densities, where formic acid appears to be an important detonation product.     

Solubility Determination of Raw Energetic Materials in Molten 2,4‐Dinitroanisole

2,4‐Dinitroanisole (DNAN) is an ingredient used in several insensitive munition formulations that have recently been qualified by the US Army. A phenomenon known as irreversible growth is found to occur during conditioning cycles of insensitive munitions (IM) that contain DNAN. A possible cause of the irreversible growth maybe the potential solubility of energetic components formulated with melted DNAN. This report documents methods development and procedures used to determine the solubility of energetic constituents in molten DNAN at 100 °C. High performance liquid chromatography and ion chromatography were used for quantitation. Solubilities (given as g energetic per 100 g DNAN) of RDX, HMX, NTO, NQ, and AP were found as 13.7, 3.02, 0.222, 0.448, and 0.088, respectively.     

Attractive Nitramines and Related PBXs

At present, cis‐1,3,4,6‐tetranitro‐octahydroimidazo‐[4,5‐d]imidazole (bicyclo‐HMX, BCHMX) and ε‐2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (ε‐HNIW, CL‐20) are a topic of interest from the attractive and the potentially attainable nitramines. They were chosen to be studied in comparison with 1,3,5‐trinitro‐1,3,5‐triazinane (RDX) and β‐1,3,5,7‐tetranitro‐1,3,5‐tetrazocane (β‐HMX). Marginal attention is devoted also to 4,8,10,12‐tetranitro‐2,6‐dioxa‐tetraazawurtzitane (Aurora 5). BCHMX, ε‐HNIW, RDX, and HMX were studied as plastic bonded explosives (PBXs) with elastic properties based on Composition C4 and Semtex 10 matrices. Also they were studied as a highly pressed PBXs based on the Viton A binder. The detonation parameters and sensitivity aspects of these nitramines and their corresponding PBXs were determined. Relative explosive strengths (RS) of these compositions are mentioned with mutual relationships between the measured RS values and some detonation parameters. These relationships indicate a possibility of changes in detonation chemistry of these mixtures filled mainly by HNIW. A sensitivity of RS‐CL20 (HNIW with reduced sensitivity) is reported and the new findings in the friction sensitivity are discussed.     

Degradation of TNT,RDX, and HMX Explosive Wastewaters Using Zero‐Valent Iron Nanoparticles

The high‐energy explosives 2,4,6‐trinitrotoluene (TNT), hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX), and the high melting explosive octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) are common groundwater contaminants at active and abandoned munitions production facilities causing serious environmental problems. A highly efficient and environmentally friendly method was developed for the treatment of the explosives‐contaminated wastewaters using zero‐valent iron nanoparticles (ZVINs). ZVINs with diameters of 20–50 nm and specific surface areas of 42.56 m² g⁻¹ were synthesized by the co‐precipitation method. The explosives degradation reaction is expressed to be of pseudo first‐order and the kinetic reaction parameters are calculated based on different initial concentrations of TNT, RDX, and HMX. In addition, by comparison of the field emission scanning electron microscopy (FE‐SEM) images for the fresh and reacted ZVINs, it was apparent that the ZVINs were oxidized and aggregated to form Fe₃O₄ nanoparticles as a result of the chemical reaction. The X‐ray diffraction (XRD) and X‐ray absorption near edge structure (XANES) measurements confirmed that the ZVINs corrosion primarily occurred due to the formation of Fe₃O₄. Furthermore, the postulated reaction kinetics in different concentrations of TNT, RDX, and HMX, showed that the rate of TNT removal was higher than RDX and HMX. Furthermore, by‐products obtained after degradation of TNT (long‐chain alkanes/methylamine) and RDX/HMX (formaldehyde/methanol/hydrazine/dimethyl hydrazine) were determined by LC/MS/MS, respectively. The high reaction rate and significant removal efficiencies suggest that ZVINs might be suitable and powerful materials for an in‐situ degradation of explosive polluted wastewaters.     

Predicting the Detonation Velocity of CHNO Explosives by a Simple Method

A simplified method is shown, based on a semi‐empirical procedure, to estimate the detonation velocities of CHNO explosives at various loading densities. It is assumed that the product composition consists almost of CO, CO₂, H₂O and N₂ for oxygen‐rich explosives. In addition solid carbon and H₂ are also counted for an oxygen‐lean explosive. The approximate detonation temperature, as a second needed parameter, can be calculated from the total heat capacity of the detonation products and the heat of formation of the explosive by PM3 procedure. The detonation velocities of some well‐known CHNO explosives, calculated by the simple procedure, fit well with measured detonation velocities and the results from the well‐established BKW‐EOS computer code.     

Study of Plastic Explosives based on Attractive Cyclic Nitramines,Part II. Detonation Characteristics of Explosives with Polyfluorinated Binders

A series of plastic bonded explosives (PBXs) based on Viton A and Fluorel binders were prepared using four nitramines, namely RDX (1,3,5‐trinitro‐1,3,5‐triazinane), β‐HMX (β‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocane), BCHMX (cis‐1,3,4,6‐tetranitro‐octahydroimidazo‐[4,5‐d]imidazole), and ε‐HNIW (ε‐2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane). The detonation velocities, D, were determined. Detonation parameters were also calculated by means of modified Kamlet & Jacobs method, CHEETAH and EXPLO5 codes. In accordance with our expectations BCHMX based PBXs performed better than RDX based ones. The Urizar coefficient for Fuorel binder was also calculated.     

Validation of DSD Relations for RDX‐TNT‐Based Cast Explosives for Lower Diameters and Dn–κ Surface Equation

In this paper, we extended our work on RDX and TNT‐based explosives to lower diameter to validate detonation shock dynamics (DSD) first‐order relationships between normal detonation velocity D_n and detonation wave curvature κ. At 25 mm diameter, we observed that D_n–κ relationship approximates, although not perfectly, the relation for 50 mm diameter. Thus to an approximation, the first order DSD theory is independent of geometry. On that basis, a general equation has been proposed, which can predict D_n–κ for RDX/TNT cast explosives in the mixing ratios 60 : 40–40 : 60.     

老化对TNT基熔铸炸药性能的影响

为了研究老化对炸药性能的影响,对自然贮存的3种熔铸炸药TNT／RDX、TNT／RDX／Al和 TNT／HMX／Al进行了加速老化试验。通过扫描电镜、真空安定性试验研究了老化前后3种炸药的微观形貌和安全性能,并测试了老化前后3种炸药的感度和爆速。结果表明,老化后炸药颜色变深,体积膨胀,质量变轻。样品的放气量小于2 mL／g ,热感度变化也较小。机械感度的变化与炸药组分和老化方式有关。TNT／RDX的爆速随着贮存时间的增加而降低,与整体加速老化情况一致,TNT／RDX／Al和 TNT／HMX／Al的爆热随贮存时间的增加变化趋势相反,说明两者老化机理可能不同。     

The Role of Aluminum in the Detonation and Post‐Detonation Expansion of Selected Cast HMX‐Based Explosives

In order to improve understanding of how aluminum contributes in non‐ideal explosive mixtures, cast‐cured formulations have been analyzed in a series of cylinder tests and plate‐pushing experiments. This study describes the contribution of 15 % aluminum (median size of 3.2 μm) vs. lithium fluoride (an inert substitute for aluminum; <5 μm) in cast‐cured HMX formulations in different temporal regimes. Small cylinder tests were performed to analyze the detonation and wall velocities (1–20 μs) for these formulations. Near‐field blast effects of 58 mm diameter spherical charges were measured at 152 mm and 254 mm using steel plate acceleration. Pressure measurements at 1.52 m gave information about free‐field pressure at several milliseconds. While the observed detonation velocities for all formulations were within uncertainty, significantly higher cylinder wall velocities, plate velocities, and pressures were observed for the aluminum formulations at ≥2 μs. Additionally, hydrocode calculations were performed to determine how non‐ideal behavior affected the plate test results. Collectively, this work gives a clearer picture of how aluminum contributes to detonation on timescales from 1 μs to about 2 ms, and how the post‐detonation energy release contributes to wall velocities and blast effects. The experiments indicate that significant aluminum reactions occur after the CJ plane, and continue to contribute to expansion at late times.     

A Discussion of the Kamlet‐Jacobs Formula for the Detonation Pressure

The main features of the Kamlet‐Jacobs formula for the detonation pressure of C H N O explosives are analytically derived from a BKW (Becker‐Kistiakowsky‐Wilson) equation of state of the detonation products. In the derivation, well‐known typical values at the Chapman‐Jouguet state, in particular the nearly constant value of the relative volume of the detonation products, are used.     

Quantum Chemical Studies on the Structure and Performance Properties of 1,3,4,5‐Tetranitropyrazole: A Stable New High Energy Density Molecule

Molecular orbital calculations were performed for the geometric and electronic structures, band gap, thermodynamic properties, density, detonation velocity, detonation pressure, stability and sensitivity of 1,3,4,5‐tetranitropyrazole ( R23 ). The calculated density (approx. 2060 kg m⁻³), detonation velocity (approx. 9.242 km s⁻¹) and detonation pressure (approx. 41.30 GPa) of the model compound are appearing to be promising compared to hexahydro‐1,3,5‐trinito‐1,3,5‐triazine (RDX) and octahydro‐1,3,5,7‐tetranitro‐l,3,5,7‐tetrazocine (HMX). Bader’s atoms‐in‐molecules (AIM) analysis was also performed to understand the nature of the intramolecular N ⋅⋅⋅ O interactions and the strength of trigger X NO₂ bonds (where XC, N) of the optimized structure computed from the B3LYP/aug‐cc‐pVDZ level.     

Review on Melt Cast Explosives

A systematic overview of melt cast explosives is given. The research on melt cast explosives over several decades can be divided into three broad areas: (i) aromatic compounds with C CH₃, N CH₃, OCH₃ C NO₂, N NO₂ and ONO₂ groups, (ii) improved synthesis of compounds, which are currently used in formulations or which have shown promise for such use and (iii) the preparation of melt cast formulations with various compositions. Exudation, high volume change from liquid to solid, super cooling, irreversible growth, fragility and unpredictable sensitivity are the disadvantages of existing melt cast formulations.     

Simultaneous Determination of Multiple Mechanical Parameters for a DNAN/HMX Melt‐Cast Explosive by Brazilian Disc Test Combined with Digital Image Correlation Method

Tensile strength, tensile modulus, compressive modulus, and Poisson's ratio are important mechanical parameters for brittle explosives. Generally, these parameters are separately measured by several different tests in which the homogeneity of specimens cannot be guaranteed, thus requiring a simultaneous determination of these mechanical parameters by one test. In this paper, simultaneous determination of multiple mechanical parameters of a DNAN/HMX melt‐cast explosive using Brazilian disc test combined with digital image correlation (DIC) method is described. The method would allow tensile strength, tensile modulus, compressive modulus, and Poisson′s ratio to be obtained simultaneously by one test, when the influences of rigid body motion have been effectively removed. The method principle was introduced in detail in this paper. The effect of temperature on the mechanical properties and the difference between the tensile modulus and compressive modulus of the DNAN/HMX melt‐cast explosive were investigated. The elastic constants and tensile strength were quantitatively analyzed and are qualitatively correct, which demonstrates the effectiveness of the presented method.