Studies on Energetic Compounds Part 23: Preparation,Thermal and Explosive Characteristics of Transition Metal Salts of 5‐Nitro‐2,4‐Dihydro‐3H‐1,2,4‐Triazole‐3‐One (NTO)

Five transition metal salts of 5‐nitro‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐one, [namely M(NTO)_n⋅mH₂O where M is Ag, Hg, Cd, Cr, Fe where n=1,2,2,3,3 and m=1,2,2,8,2 respectively] were prepared and characterized (hereafter these compounds will be named as AgNTO, HgNTO, CdNTO, CrNTO and FeNTO, respectively). Their thermal decomposition was investigated by TG, DTA whereas explosive behaviour has been studied in terms of explosion delay, impact and friction sensitivities. Further, kinetic parameters have been derived using non‐isothermal TG data and mechanism of thermolysis has also been proposed. It seems that dehydration takes place prior to the evolution of NO₂ and the subsequent ring rupture yielding metal oxide. AgNTO on the other hand yields metallic silver. Dehydration in the case of HgNTO occurs in two steps: at each step one molecule is lost. All the salts are insensitive to impact and at the same time insensitive to friction up to 360 N.     

新型叠氮-均三嗪类含能化合物的合成与表征

以三聚氯氰为前驱体,通过亲核取代反应,得到硝基芳环均三嗪中间体;再将中间体与NaN3反应,得到4种新型叠氮-均三嗪类含能化合物:4,6-二叠氮基-N-(2-硝基苯基)-1,3,5-三嗪-2-胺基、4,6-二叠氮基-N-(3-硝基苯基)-1,3,5-三嗪-2-胺基、4,6-二叠氮基-N-(4-硝基苯基)-1,3,5-三嗪-2-胺基、2,4-二叠氮基-6-(2-(2,4-二硝基苯基)肼基)-1,3,5-三嗪;采用IR、1 H NMR、13 C NMR、MS等对4种化合物的结构进行了表征;采用TG-DSC研究了4种化合物的热力学性能;通过B3LYP/6-311G**方法预估了化合物的理论密度、标准生成焓、爆速和爆压。结果表明,4种化合物具有较好的热稳定性,叠氮基的引入使其具有较高的正生成焓。综合4种叠氮-均三嗪类含能化合物的性能,化合物2,4-二叠氮基-6-(2-(2,4-二硝基苯基)肼基)-1,3,5-三嗪的性能较佳。     

Dinitrophenyl Triazoles – “A Class of Energetic Azoles”: Synthesis,Characterisation, and Performance Evaluation Studies

Energetic azoles have shown great potential as powerful energetic molecules, which find various applications in both military and civilian fields. This work describes the synthesis, characterization and performance evaluation of two energetic triazole derivatives, viz. N‐(2,4‐dinitrophenyl)‐3‐nitro‐1H‐1,2,4‐triazole ( 1a ) and N‐(2,4‐dinitrophenyl)‐3‐azido‐1H‐1,2,4‐triazole ( 1b ). The compounds were synthesized from 3‐nitro‐1,2,4‐triazole and 3‐azido‐1,2,4‐triazole, by a simple synthetic route and structurally characterized using FT‐IR and NMR (¹H, ¹³C) spectroscopy as well as elemental analysis. Thermal analyses on the molecules were performed using simultaneous TG‐DTA. Both compounds ( 1a , 1b ) showed good thermal stability with exothermic decomposition peaks at 348 °C and 217 °C, respectively, on DTA. The energetic and sensitivity properties of both compounds like friction sensitivities and heats of formation are reported. The heats of combustion at constant volume were determined using oxygen bomb calorimetry and the results were used to calculate the standard molar heats of formation (Δ_fH^m). The azido derivative ( 1b ) showed a higher positive heat of formation. The thermo‐chemical properties of the compounds as well as the thermal decomposition products were predicted using the REAL thermodynamic code.     

Coating of Energetic Materials using Crystallization

A sensitive explosive was coated with a less sensitive explosive in order to improve stability while maintaining explosion performance. In this study the sensitive explosive HMX was coated with the less sensitive explosive NTO (3‐nitro‐1, 2, 4‐triazole‐5‐one) by cooling crystallization. The mechanism of coating by crystallization was determined to be an agglomeration and crystal growth phenomenon. The surface morphology and the growth rate of the coating were investigated under various experimental conditions. The surface morphology was predominantly influenced by the solvent type, HMX/NTO ratio, agitation speed, and degree of sub‐cooling. The growth rate of the HMX coating was increased to a certain extent by increasing the concentration ratio of HMX/NTO, but then began to decrease because of high agglomeration. Finally, the optimal conditions to achieve thin and uniform surface coatings on HMX were found experimentally.     

Preparation and Properties of An Insensitive Booster Explosive Based on LLM‐105

A new insensitive booster explosive based on 2,6‐diamino‐3,5‐dinitropyrazing‐1‐oxide (LLM‐105) was prepared by a solvent‐slurry process with ethylene propylene diene monomer (EPDM) as binder. SEM (scanning electron microscopy) was employed to characterize the morphology and particle size of LLM‐105 and molding powder. The mechanical sensitivity, thermal sensitivity, shock wave sensitivity, and detonation velocity of the LLM‐105/EPDM booster were also measured and analyzed. The results show that both mechanical sensitivity and thermal sensitivity of LLM‐105/EPDM are much lower than that of conventional boosters, such as PBXN‐5 and A5. Its shock wave sensitivity is also lower than that of PBXN‐5 and PBXN‐7. When the density of charge is 95 % TMD, its theoretical and measured detonation velocities are 7858 m s⁻¹ and 7640 m s⁻¹, respectively. These combined properties suggested that LLM‐105/EPDM can be used as an insensitive booster.     

Insensitive High Explosives II: 3,3′‐Diamino‐4,4′‐azoxyfurazan (DAAF)

This paper reviews the synthesis, properties, performance, and safety of the insensitive explosive 3,3′‐diamino‐4,4′‐azoxyfurazan (DAAF, C₄H₄N₈O₃), CAS‐No. [78644‐89‐0], and 18 formulations based on it. Though having a moderate crystal density only, DAAF offers high positive heat of formation and hence superior performance when compared with TATB. It is friction and impact insensitive but is more sensitive to shock than TATB and has an exceptionally small critical diameter and performs very well at low temperatures unlike other insensitive explosives. 39 references to the public domain are given. For Part I see Ref. [1].     

唑、嗪和呋咱类富氮化合物热行为研究进展

综述了近年来国内外关于唑、嗪和呋咱类富氮化合物热行为的研究进展,分析总结了热行为研究的方法,得出了化合物结构和取代基团对化合物热稳定性的影响规律。研究表明,富氮化合物热稳定顺序为:呋咱类嗪类唑类;三唑四唑五唑;三嗪四嗪,这是由于含碳量、骨架张力和共平面等因素引起的。引入硝基、偶氮键、氰基和叠氮基等含氮基团会降低热稳定性,这是由于取代基团的吸电子效应引起的。富氮环之间的共轭效应可以有效增强分子化合物的热稳定性。指出将热分析与理论计算及气相色谱结合来推断反应机理是未来相关研究的一个方向。     

Synthesis,Characterization, and Energetic Properties of N‐Rich Salts of the 4,5‐Dicyano‐2H‐1,2,3‐triazole Anion

The synthesis and characterization of the 4,5‐dicyano‐2H‐1,2,3‐triazole anion in its 5‐aminotetrazole, 1,5‐diaminotetrazole, and 1,5‐diamino‐4‐methyl‐tetrazole salts are reported. All compounds were characterized by IR, ¹H NMR, and ¹³C NMR spectroscopy, as well as elemental analyses. Their thermal decompositions were investigated by TG‐DSC. The densities, combustion heats, and sensitivity properties were tested. Additionally, enthalpies of formation, detonation pressures, detonation velocities, and heats of detonation were calculated. The compounds have potential application in the energetic materials field.     

Miscibility enhancement of supramolecular polymer blends through complementary multiple hydrogen bonding interactions

We have investigated the miscibility behavior and specific interactions of supramolecular poly[vinylbenzylthymine‐co‐(butyl methacrylate)] (T‐PBMA) and poly[(2‐vinyl‐4,6‐diamino‐1,3,5‐triazine)‐co‐styrene] (VDAT‐PS) blends with respect to their vinylbenzylthymine (VBT) and 2‐vinyl‐4,6‐diamino‐1,3,5‐triazine (VDAT) contents. Fourier transform infrared spectroscopy revealed that multiple hydrogen bonding interactions occurred exclusively between the VDAT and VBT units, which were stronger than adenine and thymine interactions. A miscibility window occurred in the VDAT‐PS/T‐PBMA blend system when the VBT and VDAT fractions in the copolymers were greater than 7 mol%, as predicted using the Painter–Coleman association model. Copyright © 2010 Society of Chemical Industry     

Stabilization of Nitro‐Aromatics

For a variety of reasons, including U.S. Federal law and improved safety, it is desirable to have insensitive munitions (IM). Although a variety of methods are available to reduce the sensitivity of munitions only changes to the high explosive (HE) itself result in increased safety during storage, transportation, handling, and deployment. As a result of this IM are almost always filled with fire resistant, shock resistant insensitive HE such as triaminotrinitrobenzene (TATB). The high cost of TATB has limited its use. In this study we examine 28 nitro‐aromatics, including TATB and five previously unpublished structures, in the solid state in order to identify forces that stabilize the HE. We show that the sum of forces involved in crystal packing (i.e. the estimated energy of stabilization) has a direct relationship to the observed sensitivity of nitro‐aromatic explosives.     

Studies of Novel Heterocyclic Insensitive High Explosive Compounds: Pyridines,Pyrimidines, Pyrazines and Their Bicyclic Analogues

The rationale behind using heterocyclic compounds [1], particularly nitrogen heterocycles, as higher energy insensitive high explosives is discussed, including the potential advantages compared with carbocyclic compounds. The types of functional groups used to impart energy to heterocyclic nuclei, whilst maintaining insensitivity, and methodologies for their introduction, are covered. The latter include nitration (by conventional and clean synthetic methods), amination, and oxidation (on ring heteroatoms and of exocyclic amino groups). Strategies for maximising the energetic content of a given heterocyclic nucleus are also examined. The syntheses of specific examples at QinetiQ are described, based on the following nuclei: pyridine, pyrimidine, pyrazine, quinoxaline, quinazoline, pteridine and purine. Strategies for obtaining the desired amino‐nitro derivatives and their heterocyclic N‐oxides are outlined. Optimisation of the synthetic routes for several candidates is discussed. The physical, explosive and thermal properties of the more successful candidates are described, with suggestions for their potential application in military stores.     

Preparation,Characterization, and Sensitivity Data of Some Azidomethyl Nitramines

1,3‐Diazido‐2‐nitro‐2‐azapropane (DANP) and 1,7‐diazido‐2,4,6‐trinitro‐2,4,6‐triazaheptane (DATH) were synthesized, thoroughly analyzed, and their explosive properties and sensitivities toward friction and impact were measured. The precursors 1,3‐diacetoxy‐2‐nitro‐2‐azapropane ( 1 ), 1,3‐dichloro‐2‐nitro‐2‐azapropane ( 3 ), and 1,7‐dichloro‐2,4,6‐trinitro‐2,4,6‐triazaheptane ( 4 ) – as well as DATH – were furthermore characterized by X‐ray diffraction.     

4,5‐Bis(5‐tetrazolyl)‐1,2,3‐triazole: Synthesis and Performance

4,5‐Bis(5‐tetrazolyl)‐1,2,3‐triazole (BTT) was synthesized by a new method. Its structure was characterized by IR and ¹³C NMR spectroscopy and elemental analysis (EA). The thermal stability of BTT was investigated by TG‐DSC technique. The kinetic parameters including activation energy and pro‐exponential factor were calculated by Kissinger equation. The combustion heat, detonation products, hygroscopicity, impact, and friction sensitivity were also measured. The formation heat, detonation pressure, and detonation velocity of BTT were calculated. BTT has high detonation pressure and detonation velocity (P=35.36 GPa, D=8.971 km s⁻¹). BTT has potential application prospect as environmentally friendly gas generant, insensitive explosive and solid propellant.     

Estimating Ambient Vapor Pressures of Low Volatility Explosives by Rising‐Temperature Thermogravimetry

Vapor pressure is a fundamental physical characteristic of chemicals. Some solids have very low vapor pressures. Nevertheless numerous chemical detection instruments aim to detect vapors. Herein we address issues with explosive detection and use thermogravimetric analysis (TGA) to estimate vapor pressures. Benzoic acid, whose vapor pressure is well characterized, was used to calculate instrumental parameters related to sublimation rate. Once calibrated, the rate of mass loss from TGA measurements was used to obtain vapor pressures of the 12 explosives at elevated temperature: explosive salts – guanidine nitrate (GN); urea nitrate (UN); ammonium nitrate (AN); as well as mono‐molecular explosives – hexanitrostilbene (HNS); cyclotetramethylene‐tetranitramine (HMX), 4,10‐dinitro‐2,6,8,12‐tetraoxa‐4,10‐diaza‐tetracyclododecane (TEX), cyclotrimethylenetrinitramine (RDX), pentaerythritol tetranitrate (PETN), 3‐nitro‐1,2,4‐triazol‐5‐one (NTO), 1,3,3‐trinitroazeditine (TNAZ), triacetone triperoxide (TATP), and diacetone diperoxide (DADP). Ambient temperature vapor pressures were estimated by extrapolation of Clausius‐Clapeyron plots (i.e. ln p vs. 1/T). With this information potential detection limits can be assessed.     

A simple imide compound as a curing agent for epoxy resin. I. Synthesis and properties

A simple imide compound, 4‐amino‐phthalimide (APH), was synthesized as a curing agent for epoxy resin. APH was prepared from the hydration of 4‐nitro‐phthalimide, which was prepared from the nitration of phthalimide. The chemical structure of APH was verified by IR and ¹H‐NMR spectra. The thermal properties and dielectric constant (ε) of a phosphorus‐containing novolac epoxy resin cured by APH were determined and compared with those of epoxy resins cured by either 4,4′‐diamino diphenyl methane (DDM) or 4,4′‐diamino diphenyl sulfone (DDS). The results indicate that the epoxy resin cured by APH showed better thermal stability and a lower ε than the polymer cured by either DDM or DDS. This was due to the introduction of the imide group of APH into the polymer structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Size Reduction of Particulate Energetic Material

The size reduction by dispersers in the liquid phase was investigated for different energetic materials such as hexogen (RDX), octogen (HMX), 3‐nitro‐1,2,4‐triazole‐5‐one (NTO), hexanitrostilbene (HNS), ammonium nitrate (AN) and hexanitrohexaazaisowurtzitane (CL20). Two different dispersers, an ultrasonic device and a rotor stator milling device, were used. Changes in the mean particle size and particle size distribution during the comminution could be observed. The use of different ultrasonic intensities for the ultrasonic comminution yields different size reduction results. Induction of ultrasound into a liquid phase was optically investigated in liquids of different viscosity.     

A Novel Cocrystal Explosive of HNIW with Good Comprehensive Properties

In order to improve the safety of the high explosive 2,4,6,8,10,12‐hexanitrohexaazaisowurtzitane (HNIW), we cocrystallized HNIW with the insensitive explosive DNB (1,3‐dinitrobenzene) in a molar ratio 1 : 1 to form a novel cocrystal explosive. Structure determination showed that it belongs to the orthorhombic system with space group Pbca. Therein, layers of DNB alternate with bilayers of HNIW. Analysis of interactions in the cocrystal indicated that the cocrystal is mainly formed by hydrogen bonds and nitro‐aromatic interactions. Moreover, the thermal behavior, sensitivity, and detonation properties of the cocrystal were evaluated. The results implied that the melting point of the cocrystal is 136.6 °C, which means an increase of 45 °C relative that of pure DNB. The predicted detonation velocity and detonation pressure of the cocrystal are 8434 m s⁻¹ and 34 GPa, respectively, which are similar to that of the reported HNIW/TNT cocrystal, but its reduced sensitivity (H₅₀=55 cm) makes it an attractive ingredient in HNIW propellant formulations.     

1,3,5‐Trinitroperhydro‐1,3,5‐triazine (RDX)‐Based Sheet Explosive Formulation with a Hybrid Binder System

A plastic‐bonded explosive (PBX) in the form of a sheet was formulated comprising of 1,3,5‐trinitroperhydro‐1,3,5‐triazine (RDX) and an hybrid binder system containing a linear thermoplastic polyurethane and a fluoroelastomer (Viton). The effect of a fluoroelastomer on the explosive as well as mechanical properties and thermal behavior of sheet explosive formulations were investigated and compared with a control formulation containing 90 % of RDX and 10 % of natural rubber (ISNR‐5). The replacement of 10 % natural rubber by a hybrid binder system led to an increase in the velocity of detonation (VOD) of the order of 250–950 m s⁻¹ and better mechanical properties in terms of tensile strength (1.9–2.5 MPa) compared to the control formulation (RDX/ISNR‐5 (90/10)). The compatibility of ingredients and thermal decomposition kinetics of selected sheet explosive formulations were investigated by vacuum stability tests and differential scanning calorimetry (DSC). The results suggested better compatibility of RDX with the hybrid binder system (polyurethane/Viton), which is useful to reduce potential hazards in handling, processing, and storage.     

The Development of a New Synthesis Process for 3,3′‐Diamino‐4,4′‐azoxyfurazan (DAAF)

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.     

无氯TATB的合成进展

根据国内外文献,综述了钝感炸药TATB的合成方法,介绍了几种含氯TATB改进的合成方法,着重讨论采用不同原料和路线合成无氯TATB的进展,特别介绍了利用氢的VNS直接胺化法合成TATB的原理和有关工艺路线,包括反应原材料、物料配比、胺化剂及其加入方式、淬灭反应的方法对产物得率、粒度、纯度和表观形貌的影响。VNS法是合成多硝基多氨基硝基芳烃类含能材料的一种新方法。