Reduced Sensitivity RDX Obtained From Bachmann RDX

In recent years much interest has been generated in a quality of reduced sensitivity RDX (RS‐RDX), like I‐RDX^® which, when incorporated in cast cure and even pressable plastic bonded explosives (PBX compositions), can confer reduced shock sensitivity as measured through gap test. At crystal level, lot of work has been done to try to determine which property or properties may explain the behaviour of the corresponding cast PBX composition. But up to now, and despite an international inter‐laboratory comparison (Round Robin) of seven lots of RDX from five different manufacturers conducted from 2003 to 2005, even if some techniques lead to interesting results, there is no dedicated specification to apply to RS‐RDX. This quality (I‐RDX^®) has proved to retain its low sensitivity even after ageing, which does not seem to be the case for standard RDX produced by the Bachmann process (when re‐crystallized under I‐RDX conditions in order to obtain RS‐RDX). It has been shown that the higher sensitivity of RDX produced by the Bachmann process, or the evolution of sensitivity after ageing of RS‐RDX produced from Bachmann RDX may be linked to the presence of octogen (HMX) during the crystallization process. In order to check such hypothesis, low HMX content RDX produced by the Bachmann process has been prepared and evaluated in cast PBX composition (PBX N 109). Results of the characterization of such quality of RDX and its evaluation in cast PBX composition as well as ageing behaviour are presented and discussed; there are indications that removal of HMX from Bachmann RDX may lead to RS‐RDX, which retains its RS character even after ageing.     

RDX and HMX with Reduced Sensitivity Towards Shock Initiation–RS‐RDX and RS‐HMX

Reduced Sensitivity RDX (RS‐RDX) has received a lot of attention and interest from the explosive community in the recent years. There are several producers of RS‐RDX, most of them using a direct nitration (Woolwich process) for the RDX synthesis, while Chemring Nobel uses the Bachmann process. The processes for obtaining the RS properties probably differ between the various producers. Chemring Nobel has also developed an HMX quality that shows Reduced Sensitivity (RS‐HMX) of different particle size distributions. The shock sensitivity is at the same level as for RS‐RDX in comparable compositions. Reduced shock sensitivity has been obtained for RS‐RDX and Reduced Sensitivity (RS‐HMX) in both pressable and cast‐cured compositions. By using a pressable composition, it is possible to get the results from a BICT gap test faster than from a cast‐cured composition that has to go through a curing process. Chemring Nobel in cooperation with FFI have performed an extensive accelerated ageing testing of RS‐RDX produced by the Bachmann process. The samples have been aged at 60 and 70 °C and the shock sensitivity tested by two different gap tests. The results demonstrate that the Chemring Nobel RS‐RDX retain the insensitivity towards shock during ageing and show no degradation at all. Accelerated ageing testing of RS‐HMX has also been performed and shows no degradation in the shock sensitivity.     

Research on the Size of Defects inside RDX/HMX Crystal and Shock Sensitivity

Intragranular defects inside RDX/HMX were studied by optical microscopy with matching refractive (OMS), sink‐float method (SFM), and micro‐focus CT (μCT) techniques. OMS results revealed the phenomenon that RDX/HMX had more defects and cracks than RS‐RDX/RS‐HMX. μCT results indicated that RDX/HMX had more defects with larger volume than RS‐RDX/RS‐HMX. The gap test showed that critical shock pressure/gap thickness was 6.4 GPa/19.4 mm for PBX based on RDX, while they were 7.5 GPa/17.5 mm and 8.6 GPa/16.2 mm for PBX based on M‐RDX and RS‐RDX, respectively. Meanwhile, an analysis of the relationship between defects inside RDX/HMX crystal and shock sensitivity was made. Finally, the shock pressure response under impact loading was investigated by discrete element method.     

纳米HMX/微米RDX复合炸药撞击感度的性能研究

在超声波的环境下制备了不同配比的纳米HMX(奥克托今)/微米RDX(黑索今)复合炸药,并对纯RDX炸药和自制炸药的撞击感度进行了比较。结果发现,在实验配比范围内,纳米HMX/微米RDX复合炸药比纯RDX炸药敏感,且随HMX含量的增加,撞击感度降低。     

超细HMX和RDX撞击感度的研究

利用爆炸概率法对超细奥克托今（ＨＭＸ）和黑索今（ＲＤＸ）的撞击感度进行了研究。试验结果表明：超细ＨＭＸ和ＲＤＸ的爆炸分数相比军用标准样品的值有较大幅度下降。文章分析了撞击感度降低的原因,并展望了超细炸药在高能量、低感度炸药研制中的重要意义。     

Characterization of Granular and Polymer‐Embedded RDX Grades: Floret Tests

In an attempt to further contribute to the characterization of explosive compositions, small scale Floret tests were performed using four RDX grades, differing in product quality. A Floret test provides a measure – by indentation of a copper block – of detonation spreading or the initiability and shock wave divergence and is applied in particular to explosives used in initiation trains. Both as‐received RDX and PBXs (based on the AFX‐757 composition, a hard target penetrator explosive) containing these RDX grades were tested in the Floret test set‐up. It was found that the Floret test method, when applied to granular, as‐received RDX, was not able to discriminate between the overall RDX product qualities on the basis of the resulting volume of the indentation in the copper block. For the Floret test data of the PBX samples, a division into two parts, where one of the RDX lots shows a lower dent volume compared to the other RDX lots tested. Based on the results presented in this paper with granular RDX and a PBX composition and earlier results with a different type of PBX (based on PBXN‐109, an insensitive high explosive used in a wide range of munitions), the Floret test could be developed into a screening test for shock sensitivity and product quality, without the need for complex and large volume casting of specific PBX compositions.     

Investigating the Mechanical Properties of RDX Crystals Using Nano‐Indentation

The shock sensitivity of RDX is of major interest for the development of insensitive munitions. Previous research has implied that internal defects that form within RDX crystals have a strong sensitising effect, increasing the probability of shock initiation. During the NATO Reduced sensitivity RDX Round Robin (R⁴) program the number of internal defects within RDX crystals of differing qualities were assessed by optical microscopy and a scoring system. The results suggested that RDX crystals with many internal defects were more sensitive. Studies investigating the mechanical properties of bulk RDX have shown that lots consisting of poorer crystals are weaker. This study investigates the mechanical properties of individual crystals from different RDX lots using nano‐indentation. It is shown that crystals with many internal defects have reduced modulus of elasticity, stiffness and prone to greater deformation under applied load. The results also show a correlation between these parameters and previously reported shock sensitivity data.     

热红联用研究AP与RDX和HMX混合体系的热分解

用DSC—TG—FTIR（热红）联用研究了RDX／AP，HMx／AP，RDx／HMx和RDX／HMX／AP混合体系的热分解，测定和比较了它们的热分析特征量和分解气相产物。结果表明，AP与RDX和HMX之间存在强烈的相互作用，尤其是与后者的作用更强烈。在AP（不含碳）分解的温度区间，混合体系的分解也出现CO、CO2和CH2O等碳氧化物，说明体系中RDX和HMX分解的部分产物或残渣与AP同时分解。     

On the Reliability of Sensitivity Test Methods for Submicrometer‐Sized RDX and HMX Particles

Submicrometer‐sized RDX and HMX crystals were produced by electrospray crystallization and submicrometer‐sized RDX crystals were produced by plasma‐assisted crystallization. Impact and friction sensitivity tests and ballistic impact chamber tests were performed to determine the product sensitivity. Rather than reflecting the quality of the particles, we found the sensitivity tests to be unreliable for submicrometer particles. The used impact test was not accurate enough, while in the friction and ballistic impact chamber tests the submicrometer‐sized crystals were distributed among the grooves of the porcelain plate or among the grains of the sandpaper used in these tests. These observations stress the need for revisiting the current standards used for determining the hazardous properties like friction and impact sensitivity of energetic materials in the case, where the sample consists of submicrometer‐sized crystals. Recommendations were suggested to develop new test methods that only use the interactions between the particles and therefore allow the application of sensitivity tests for submicrometer/nano‐sized energetic materials.     

RDX和HMX单晶的压痕断裂韧性

使用纳米压痕仪在HMX、RDX单晶表面进行压痕实验,并用不同压痕方程计算了单晶的断裂韧性.计算得到HMX晶体(010)面与RDX晶体(020)、(210)面间断裂韧性分别力0.092543、0.097387、0.10072 MPa·m1/2.结果表明,实验单晶的KIC值遵循Palmqvist系裂纹系统shetty方程,...     

Physicochemical Parameters of Nitramines Influencing Shock Sensitivity

TNO Prins Maurits Laboratory has actively followed and contributed to the research on the development of insensitive munitions (IM). One of the initial research topics at TNO focused on the improvement of the shape of RDX crystals and its relation to the shock sensitivity. The variation of crystal shape has been studied by crystallization from different solvents and/or by post‐treatment of the crystals. The role of the mean particle size on shock sensitivity was also included in these analyses. The decrease in shock sensitivity is even more pronounced when controlling the internal quality of crystals. In the meantime research has shifted to other energetic materials as well – in particular HMX and CL‐20 – in this way revealing step by step the important physicochemical parameters which play a role in determining the shock sensitivity of formulations containing these types of nitramines. Various characterization techniques, to determine the internal and external quality of crystals will be discussed, and their relation to shock sensitivity in PBXs will be shown. Two different grades of I‐RDX have been subjected to different characterization tests. The objective is to gain more understanding about which of the physicochemical parameters enables one to discriminate between a reduced sensitivity RDX and normal RDX.     

Statistical Assessment Methods for the Sensitivity of Energetic Materials

The joint research project Particle Processing and Characterization was started in March 2003 under the EUROPA ERG1 Arrangement, with the objective to study the influence of crystallization and processing techniques on particle quality and its implication for the formulation of PBX with IM behavior. As sensitivity assessment is a crucial task of the project, impact sensitivity tests of HMX and RDX samples have been performed at two different laboratories, and several statistical techniques have been tested in addition to the standard BAM “1/6” and Bruceton “up and down” methods.     

EAK基熔铸分子间炸药的能量和撞击感度

通过水下爆炸试验研究了RDX和HMX对EAK基熔铸分子间炸药水下能量的影响。结果表明,RDX和HMX对EAK基混合炸药起到明显的增能作用,但对含铝和非含铝体系有不同的作用效果。爆速和撞击感度测定表明,EAK—RDX混合炸药爆轰的理想化程度和稳定性及撞击感度随RDX含量的增加而增加。从能量和撞击感度两个方面综合考虑,RDX的较佳加入量应为20％～30％。     

Smokeless GAP‐RDX Composite Rocket Propellants Containing Diaminodinitroethylene (FOX‐7)

Composite rocket propellants prepared from nitramine fillers (RDX or HMX), glycidyl azide polymer (GAP) binder and energetic plasticizers are potential substitutes for smokeless double‐base propellants in some rocket motors. In this work, we report GAP‐RDX propellants, wherein the nitramine filler has been partly or wholly replaced by 1,1‐diamino‐2,2‐dinitroethylene (FOX‐7). These smokeless propellants, containing 60% energetic solids and 15% N‐butyl‐2‐nitratoethylnitramine (BuNENA) energetic plasticizer, exhibited markedly reduced shock sensitivity with increasing content of FOX‐7. Conversely, addition of FOX‐7 reduced the thermochemical performance of the propellants, and samples without nitramine underwent unsteady combustion at lower pressures (no burn rate catalyst was added). The mechanical characteristics were quite modest for all propellant samples, and binder‐filler interactions improved slightly with increasing content of FOX‐7. Overall, FOX‐7 remains an attractive, but less than ideal, substitute for nitramines in smokeless GAP propellants.     

RDX和HMX的热分解Ⅲ.分解机理

简述RDX和HMX热分解的各种机理,其热分解的初始过程是N—N和C—N键断裂的竞争反应,试验条件和样品相态等因素影响竞争过程。用DSC—FTIR联用技术和热裂解原位池／FTIR分析了主要分解气相产物和凝聚相中主要官能团的变化。结果表明,RDX和HMX热分解的主要分解气相产物为N2O,CH2O,CO,CO2,H2O和HCN。RDX的分解气相产物CH2O和H2O红外吸收率的温度关系曲线都产生双峰,RDX基团-NNO2的吸收带1589cm^-1和1278cm^-1有两个不同速率的变化过程。用N—N键和C—N键竞争断裂的观点解释了RDX与HMX热分析和产物分析的结果。     

撞击加载下炸药晶体的破碎特征

分别对AP、HMX、RDX晶体进行落锤撞击加载,用环境扫描电镜观察了3种晶体的破碎特点。实验结果显示:3种晶体虽然都出现剪切带,但在破碎特征方面有明显不同,其中AP以晶体的局部脆性断裂为主,晶体的破碎程度最小,且加载后仍呈颗粒状;HMX和RDX以晶体的塑性变形和破碎为主,且加载后多呈现"薄片"结构;加载后RDX晶体比HMX易分散,但HMX晶体的破碎程度更严重。研究认为:晶体的撞击加载是力-热转化过程,晶体内部热点形成与晶体的力学强度有关,认为这一转换过程与晶体的分子组成和热反应机理有关。在低速撞击加载下,具有较强分子稳定性的AP晶体破碎程度最小,且不易形成热点。对于RDX和HMX晶体,"薄片"结构的形成原因除晶体破碎外,内部还可能存在相变、转晶等变化。     

The Decomposition of some RDX and HMX Based Materials in the One‐Dimensional Time to Explosion Apparatus. Part 1. Time to Explosion and Apparent Activation Energy

A One‐Dimensional Time to Explosion (ODTX) apparatus has been used to study the times to explosion of a number of compositions based on RDX and HMX over a range of contact temperatures. The times to explosion at any given temperature tend to increase from RDX to HMX and with the proportion of HMX in the composition. Thermal ignition theory has been applied to time to explosion data to calculate kinetic parameters. The apparent activation energy for all of the compositions lay between 127 kJ mol⁻¹ and 146 kJ mol⁻¹. There were big differences in the pre‐exponential factor and this controlled the time to explosion rather than the activation energy for the process.     

RDX和HMX的热分解I.热分析特征量

用PDSC和TG-DTG研究了RDX和HMX的热分解,探讨了各种试验条件,包括试样量、升温速率和动静态高压等的影响。在分解过程中相态变化引起反应的加速是HMX的分解较RDX剧烈的主要原因,HMX的自加热和自催化也因此变得较RDX更显著。     

RDX和HMX的热分解II.动力学参数和动力学补偿效应

用DSC、DTA和TG-DTG技术测定了RDX和HMX热分解的动力学参数。RDX和HMX在不同的分解阶段有不同的动力学参数和机理函数,其分解过程和动力学参数受试验条件、样品状态和试验方法的影响很大,但这些参数之间存在"动力学补偿效应"和"等动力学点"。     

β-环糊精与RDX,HMX的包合研究

通过测定溶液的紫外吸收光谱,得到了β-环糊精(β-CD)与RDX,HMX的最佳包合比为1∶1;采用饱和溶液法对β-环糊精与含能材料RDX,HMX进行包合,得到了β-环糊精与RDX、HMX的固体包合产物;通过测定固体产品的X-射线衍射,证明了包合物的形成。