Partial Reparametrization of the BKW Equation of State for DNAN‐Based Melt‐Cast Explosives

DNAN‐based melt‐cast explosives are a type of new, insensitive munitions (IM) explosives. Quickly determining munitions’ explosive properties is extremely important during the formulation design stage. The aim of this study was to partially reparameterize BKW‐EOS (only β and κ were reparameterized on the basis of the parameters (α , β , κ , and θ ) of classical BKW‐RDX set and BKW‐TNT set) to more accurately predict the properties of DNAN‐based melt‐cast explosives. A new set of parameters β and κ was obtained (β =0.19, κ =9.81) according to measured detonation velocity and detonation pressure for ideal DNAN‐based melt‐cast formulations (DNAN/RDX and DNAN/HMX). For non‐ideal DNAN‐based melt‐cast formulations (DNAN/RDX/Al and DNAN/HMX/Al), aluminum oxidation degree was first determined according to the measured detonation heat; then, another new set of parameters β and κ was obtained in the same way as the ideal formulations (β =0.24, κ =8.5). The predicted detonation properties with BKW reparametrization for DNAN‐based melt‐cast explosives agreed with the measured data.     

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.     

TNT、DNAN和DNTF单质凝固过程中温度和缩松的数值模拟及实验研究

为了解熔铸载体炸药凝固过程中温度及缩松规律,以TNT、DNAN和DNTF 3种单质炸药为研究对象,使用铸造软件ProCAST对3种载体在铜模具中自然凝固时轴向不同位置处温度变化及总体缩松情况进行了模拟计算,并针对模拟工况进行了试验验证;通过热电偶温度传感器测量并记录温度曲线;对凝固后的药柱进行机械剖分并观察缩松情况。结果表明,TNT、DNAN和DNTF的凝固点分别为81、90和109℃;TNT及DNAN凝固偏向于逐层凝固,而DNTF凝固则接近于体积凝固;3种单质炸药凝固过程中温度模拟结果准确度高,平均误差均小于10%;缩松预测计算结果同试验结果一致;模拟计算精度能够满足工艺实践的需求。     

国外二硝基茴香醚基炸药发展现状

为及时了解国外二硝基茴香醚(DNAN)炸药技术的发展现状,在系统跟踪国外技术文献和研发动态的基础上,综述了DNAN基炸药的配方设计、制备工艺、环境健康评估和装备应用等最新研究与进展。从中分析得出:美国DNAN基炸药技术发展最迅速,DNAN基炸药配方研究活跃,有多种配方已达到实用化水平;DNAN基熔铸炸药的环保和安全特性明显优于TNT,预示着其在不敏感弹药中具有广泛的应用前景;美军率先大规模装备IMX-101和IMX-104炸药并部署部队,标志着大口径炮弹炸药主装药的不敏感化换装已进入实施阶段;对DNAN的研究提出了建议,应重点发展DNAN基高性能熔铸炸药配方、先进制备工艺技术及应用技术。     

Preparation and Characterization of Nanoenergetics Based Composition B

Explosive compositions employing nanoscale crystals of high explosives (i. e., nanoenergetics) have demonstrated reduced sensitivities to external stimuli. Until recently, the investigated formulations were limited to plastic bonded explosives. Explosives that are normally melt‐cast also would benefit from the use of nanoenergetics. However, the integration of nanoenergetics into the melt‐cast process is challenging due to the large surface area and solubility associated with nanoenergetics. In this work, we explored the preparation of nanoenergetics‐based Composition B (Comp B), a widely used melt‐cast explosive, by spray drying followed by mechanical compaction. The Comp B molding powder obtained from spray drying was characterized by scanning electron microscopy (SEM) and X‐ray diffraction (XRD). The structure and the shock sensitivity of the compacted nanoenergetics‐based Comp B (N‐Comp B), both as‐prepared and thermally cycled, was also studied using melt‐cast Comp B as the reference material. The characterization shows that N‐Comp B consisting of nanoscale cyclotrimethylenetrinitramine (RDX) and trinitrotoluene (TNT) contains mostly nanoscale voids but has a large number density. Reduced shock sensitivity was observed from N‐Comp B, attributed to the elimination of large voids. But the decrease seems to have been constrained by the large number density of voids. Thermal cycling induced significant structural change, i. e., the increase of both void size and the crystal size, causing an increase in sensitivity. Procedures are proposed to further reduce the sensitivity and enhance the thermal stability of N‐Comp B.     

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。     

熔铸混合炸药用载体炸药评述

介绍了TNT、3号炸药、DNTF、TNAZ、DNAN、DNP等典型熔铸载体炸药的物化性能、爆炸性能、安全性能、结晶和凝固性质铸装质量,分析了作为载体炸药所存在的优点和不足,提出了利用优势克服不足的途径.认为TNT通过改性仍然是熔铸炸药的主要载体炸药;3号炸药具有系统研究的必要;DNTF通过降低冲击波感度和强化结晶控制研...     

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.     

Thermal Stability Studies Comparing IMX‐101 (Dinitroanisole/Nitroguanidine/NTO) to Analogous Formulations Containing Dinitrotoluene

The 2,4,6‐trinitrotoluene (TNT) replacement, IMX‐101, containing 43.5 % 2,4‐dinitroanisole (DNAN), 19.7 % 3‐nitro‐1,2,4‐triazol‐5‐one (NTO) and 36.8 % nitro‐guanidine (NQ), has been certified for use as an insensitive munition. IMX‐101 has passed standardized performance, stability, and aging tests but in some categories was not necessarily an improvement over TNT or RDX. This study compared the thermal stability of DNAN and another low‐melting nitroarene, 2,4‐dinitrotoulene (DNT). When examined individually, DNAN was more stable; but formulated in IMX‐101 with NTO and NQ, the opposite was true. In two part mixtures, NQ had a similar acceleratory effect on the decomposition of both nitroarenes, while NTO had a greater impact on DNAN than on NTO. Ammonia, a reported decomposition product of both NQ and NTO, also accelerated the decomposition of both DNAN and DNT, with a larger impact on DNAN. The formation of dinitroaniline, potentially due to the interaction between the nitroarenes and ammonia, was detected by LC/MS as a decomposition product when either nitroarene was combined with NTO and/or NQ, indicating that this molecule may play a significant role in the decomposition mechanism. While not advocating the use of DNT in insensitive munitions formulations, this study addresses the importance of chemical compatibility as a criterion for selecting replacement components in formulations.     

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.     

Effects of Aluminum Content on TNT Detonation and Aluminum Combustion using Electrical Conductivity Measurements

To improve the understanding how aluminum contributes in non‐ideal explosive mixtures, cast‐cured formulations were analyzed in a series of electrical conductivity experiments. Five types of TNT‐based aluminized explosives, with aluminum mass fractions from 0 % to 20 % were considered in this study. The electrical conductivity of the detonation products in aluminized explosives was measured using an improved conductivity measurement method. The conductivity measurement results show that the detonation process of TNT‐based aluminized explosives can be divided into two stages: the first stage is the detonation reaction of TNT, and the second stage is the combustion reaction of aluminum with the detonation products. In the first stage, the duration of the TNT detonation increases with increased aluminum content; examination of the peak conductivities of the explosives with various aluminum contents indicated that a higher aluminum content is associated with a lower peak conductivity. Additionally, the ignition time of Al in the second stage is also determined. This work not only presents a means for studying the detonation process of aluminized explosives at 0–2.21 μs, but it also verified the relationship between the aluminum content and electrical conductivity in detonation products.     

熔铸炸药的研究进展

综述了DNAN、TNAZ、DNTF、M eNQ四种可作为熔铸载体炸药的国内外研究现状,介绍了它们的合成方法、物理化学与爆轰性能、相容性、熔铸配方以及国内外在为其熔铸所做的最新研究成果,为促进上述载体炸药能更好地应用到熔铸中提供必要的参考数据。其中DNAN已经在美国投入到实际熔铸应用中,TNAZ、DNTF、M eNQ处于合成放大阶段和熔铸应用初级阶段。这些炸药的研究和应用将推动无TNT熔铸时代的到来。     

Evaluation of Plastic Bonded Explosive (PBX) Formulations Based on RDX,Aluminum, and HTPB for Underwater Applications

Aluminized high explosives are known to give better underwater performance. All explosive formulations for underwater targets are filled into warheads and shells by casting method. TNT, a high explosive is used as casting medium due to its lower melting point. Plastic bonded explosives are fast replacing TNT‐based high explosive formulations for the reasons that they are more insensitive and low vulnerable explosives with better shelf life. Few aluminized plastic bonded explosive formulations based on RDX, aluminum, and HTPB have been processed, varying the aluminum content from 0 to 35% and evaluated underwater. The present paper discusses the experimental methodology adopted to evaluate the above formulations for their ballistic parameters, viz., peak over pressure and impulse. Explosion bulge tests have been conducted with each explosive formulation and extent of bulge in test plates is presented and compared with a standard underwater explosive, viz., HBX‐3.     

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.     

Verification of the Explosive Quality of TH‐5

This paper reports the characteristics of the explosive TH‐5, recycled (recovered) trinitrotoluene (TNT) with max. 5 wt‐% of hexogen (RDX). The explosive TH‐5 was obtained by delaboration of warheads and melting of explosive charges based on TNT and RDX and by separation (extraction) of high explosive components. The thermal characteristics of pure (virgin) TNT and RDX, and recycled explosive TH‐5 are determined by differential scanning calorimetry. The possibility of processing TH‐5 by pressing and casting is also examined. The comparative analysis of sensitivity of TH‐5 and TNT to friction is determined, as well as compressibility of explosives, and the detonation velocity of pressed and cast charges. Based on the analysis of experimental results, the defense standard requirements for the quality of TH‐5 are defined and possibility of practical application of explosive TH‐5 was estimated.     

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).     

纳米压痕技术对比研究DNAN和TNT晶体的微观力学性能

通过溶剂挥发法制备了DNAN和TNT晶体;利用纳米压痕技术研究了DNAN和TNT晶体的微观力学性能(硬度和弹性模量);通过原位扫描探针成像技术(SPM)研究了DNAN和TNT晶体的压痕形貌随时间的变化差异。结果表明,DNAN晶体的平均硬度和弹性模量分别为7.82GPa和0.22GPa,TNT晶体的平均硬度和弹性模量分别为12.19GPa和0.48GPa,表明TNT抵抗变形的能力优于DNAN;随着压痕深度由118nm增至856nm,DNAN的硬度从0.61GPa降至0.22GPa;随着压痕深度由27nm增至481nm,TNT的硬度从2.9GPa降至0.48GPa,表明DNAN和TNT均存在尺寸效应。随着时间由0增至50.4min,DNAN的压痕深度由-270.99nm减至-44.28nm,TNT的压痕深度由-415.12nm减至-369.21nm,表明DNAN晶体比TNT晶体具有更明显的慢回弹性,DNAN具有更强的冲击能量吸收能力。     

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.     

Potential Use of CL‐20 in TNT/ETPE‐Based Melt Cast Formulations

An attempt was made to introduce CL‐20 in a TNT/energetic thermoplastic elastomer (ETPE)‐based melt cast formulation, to obtain an insensitive composition with reduced adverse environmental properties. A loading limit of 42% w/w of CL‐20 in melted TNT was observed, while it should have been around 70%. This paper describes the investigation that was undertaken to understand the observed phenomena. It was demonstrated that CL‐20 undergoes structural alterations in melted TNT. The relative solubility of CL‐20, RDX and HMX in melted TNT was determined and the α‐, β‐, γ‐ and ε‐CL‐20 were prepared and characterized using Raman spectroscopy and DTA. CL‐20 was mixed in melted TNT, as much as 4.2 g of CL‐20 dissolved in 100 g of TNT. This allowed a transformation from ε to β‐CL‐20 and a modification of CL‐20 particle size and distribution. The later modification induced a raise in CL‐20 specific surface and was responsible for the loading limit, while the transformation to β‐CL‐20 caused an increase in sensitivity and a decrease in density. This indicates that the use of CL‐20 in TNT melt cast is not promising. Our study also showed that CL‐20 is sensitive to morphological transformations, which should be taken into consideration in future processing using this compound.     

Effect of inert plasticizers on mechanical,thermal, and sensitivity properties of polyurethane‐based plastic bonded explosives

Mechanical, thermal, and sensitivity properties of plastic bonded explosives (PBX) depend on the type of ingredients in their formulation. Aim of the work is to develop aluminized cast PBX formulations and process conditions by using alternative inert plasticizers to have similar or better properties than PBXN‐109 without compromising sensitivity properties. Although very small portion of total production of plasticizers is used for solid rocket propellant and explosive formulations, they play very significant role in that area. Both inert and energetic plasticizers have involved propellant and explosive formulations to improve process parameters, mechanical properties, and even insensitivity properties of them. Isodecyl pelargonate and dioctyl adipate are the most preferred inert plasticizers in polyurethane based thermoset propellant and explosive formulations. In addition to them, diisononyl adipate and diisononyl phthalate were used and screened as inert plasticizer candidates for aluminized cast PBX formulations. Mechanical, thermal, and sensitivity properties of PBX formulations were studied and compared in detail. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40907.