Preparation and Properties of an AP/RDX/SiO2 Nanocomposite Energetic Material by the Sol‐Gel Method

A nanocomposite energetic material was prepared using sol‐gel processing. It was incorporated into the nano or submicrometer‐sized pores of the gel skeleton with a content up to 95 %. AP, RDX, and silica were chosen as the energetic crystal and gel skeleton, respectively. The structure and its properties were characterized by SEM, BET methods, XRD, TG/DSC, and impact sensitivity measurements. The structure of the AP/RDX/SiO₂ cryogel is of micrometer scale powder with numerous pores of nanometer scale and the mean crystal size of AP and RDX is approx. 200 nm. The specific surface area of the AP/RDX/SiO₂ cryogel is 36.6 m² g⁻¹. TG/DSC analyses indicate that SiO₂ cryogel can boost the decomposition of AP and enhance the interaction between AP and RDX. By comparison of the decomposition heats of AP/RDX/SiO₂ at different mass ratios, the optimal mass ratio was estimated to be 6.5/10/1 with a maximum decomposition heat of 2160.8 J g⁻¹. According to impact sensitivity tests, the sensitivity of the AP/RDX/SiO₂ cryogel is lower than that of the pure energetic ingredients and their mixture.     

Preparation of Nano‐Structured RDX in a Silica Xerogel Matrix

RDX is preferred as explosive in munitions due to its balance of power and sensitivity that is known to be dependent on its particle size and size distribution. In this study, we prepared nano‐sized RDX in a silica xerogel matrix using a sol‐gel method and investigated its sensitivity for explosive properties. The presence of RDX in composite xerogel was confirmed by TG‐DSC and FTIR techniques. Microstructure and porosity were characterized by transmission electron microscopy (TEM), small angle X‐ray scattering, and N₂‐physisorption techniques. TEM results showed that the size of RDX particles in the RDX‐silica composites is in the range of 10–30 nm. The sensitivity to impact and friction was found to be higher for the composites compared to raw RDX. It was also found to be significantly dependent on the acetone/TMOS ratio used in the preparation.     

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％。     

超细RDX/Ni混合炸药的制备及其撞击感度研究

以超细黑索今(RDX)为原料,在其中加入一定量、一定粒度的Ni粉,通过干混法和湿混法2种方法制备出超细RDX/Ni混合炸药,并对其撞击感度进行测试.通过分析其爆炸概率,进而得到镍粉的含量和粒度对超细黑索今(RDX)撞击感度的影响规律以及制备方式对撞击感度的影响.     

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。     

水性聚氨酯包覆黑索今的性能及影响因素研究

以水性聚氨酯(WPU)乳液作为黑索今(RDX)的包覆材料,以撞击感度和热感度作为衡量指标,采用单因素分析法优选出WPU包覆RDX的最佳工艺条件。结果表明:采用单凝聚法包覆RDX,当RDX的粒度为120~300目(铁筛网)、w(WPU)=2.0%(相对于RDX质量而言)和w(阳离子型表面活性剂)=1%(相对于物质总质量而言)时,RDX的包覆效果较好,此时包覆后RDX的撞击感度和热感度降幅较大。     

超细RDX/Al混合炸药的制备及性能

以超细RDX为主体炸药,通过添加Al粉,干法工艺制备出超细RDX/Al混合炸药;对制得的样品进行了撞击感度、摩擦感度测试。实验结果表明,相对超细RDX,超细RDX/Al混合炸药的撞击感度和摩擦感度有一定程度的降低。     

Surface Coating of RDX with a Composite of TNT and an Energetic‐Polymer and its Safety Investigation

To improve the safety of RDX (hexogen), an energetic polymer (HP‐1) was introduced to coat RDX with 2,4,6‐trinitrotoluene (TNT) by combining the solvent–nonsolvent and the aqueous suspension‐melting method. Scanning electron microscope (SEM), transmission electron microscope (TEM), and X‐ray photoelectron spectrometry (XPS) were employed to characterize the samples, and the role of HP‐1 in the coating process was discussed. The impact sensitivity, friction sensitivity, and the thermal stability of unprocessed and coated RDX were investigated, and the explosion heat of samples was also estimated. Results indicate that HP‐1 improves the wetting ability of the liquid coating material on RDX surface and reinforces the connection between RDX and the coating material. By surface coating, the impact and friction sensitivity of RDX decrease obviously; the drop height (H₅₀) is increased from 37.2 to 58.4 cm, and the friction probability is reduced from 92 to 38%. The activation energy (E) and the self‐ignition temperature increase by 10457.38 J⋅mol⁻¹ and 1.8 K, respectively. The explosion heat is reduced merely by 0.93%.     

水性聚氨酯包覆RDX的影响因素研究

以环氧有机硅复合改性的水性聚氨酯(WPU)作为黑索今(RDX)包覆剂,研究了包覆温度、WPU用量、RDX粒度及表面活性剂种类和用量对包覆后RDX机械感度、热感度和流散性的影响,并通过撞击感度测试、5s延滞期爆发点测试和金相显微镜晶型观测分析确定了较佳的包覆工艺条件。结果表明,包覆温度40℃、WPU质量分数2.0%、RDX粒度200～300目和阳离子表面活性剂质量分数0.5%～1.0%时,包覆后的RDX颗粒形状圆滑,感度较低,颗粒间包覆剂残留较少,流散性良好。     

溶胶-凝胶法制备RDX/AlOOH

以氯化铝为前驱物,N,N-二甲基甲酰胺为AlCl3.6H2O和RDX的溶剂,1,2-环氧丙烷为胶凝剂,常温常压下,采用溶胶-凝胶法制备RDX/AlOOH复合炸药,产物用超临界流体干燥后得固体粉末。用扫描电镜和DSC研究了复合炸药的形貌分析和热分解特性。测试了复合炸药的撞击感度、摩擦感度。结果表明,溶胶-凝胶法与超临界流体干燥技术相结合,可以较好地保持凝胶的多孔结构;其热分解过程不同于物理掺杂的混合炸药,DSC曲线上熔化吸热峰几近消失,RDX/AlOOH复合炸药的撞击感度和摩擦感度均较低。     

Mode I and Mode II delamination resistance and mechanical properties of woven glass/epoxy–PU IPN composites

The effect of polyurethane on the mechanical properties and Mode I and Mode II interlaminar fracture toughness of glass/epoxy composites were studied. Polyurethanes (PU) synthesized using polyols and toluene diisocyanate were employed as modifier for epoxy resin by forming interpenetrating polymer network. The PU/Epoxy IPN was used as matrix material for GFRP. PU modified epoxy composite laminates having varying PU contents were prepared. The effect of PU content on the mechanical properties like interlaminar fracture toughness (Mode I, G_1c and Mode II, G_IIc), tensile strength, flexural strength, and Izod impact strength were studied. The morphological studies were conducted on the fractured surface of the composite specimen by scanning electron microscopy (SEM). Tensile strength, flexural strength, and impact strength of PU‐modified epoxy composite laminates were found to increase inline with interlaminar fracture toughness (G_1c and G_IIc) with increasing PU content to a certain limit and then it was found to decrease with increase in PU content. It was observed that toughening of epoxy with PU increases the Mode I and Mode II delamination toughness up to 17 and 120% higher than that of untoughened composite specimen, respectively. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

纳米LaCoO3对RDX基混合炸药的热分解特性和感度的影响

用DSC和DTA研究了LaCoO3对含AP的RDX基混合炸药热分解特性的影响。结果表明,纳米LaCoO3对含有AP的RDX基爆炸混合物的热分解具有一定的催化作用;纳米LaCoO3使RDX基混合炸药的撞击感度和热感度降低,摩擦感度增大。     

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.     

氧化石墨烯对RDX/PMMA安全性能及力学性能影响

为改善RDX的安全性能和力学性能,采用乳液聚合法制备RDX/聚甲基丙烯酸甲酯/氧化石墨烯(RDX/PMMA/GO)微球,并用相同方法制备了RDX/PMMA复合粒子进行对比;通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FT-IR)和差示扫描热量仪(DSC)对样品进行表征,并测试其撞击感度和药柱的静态力学性能。结果表明,包覆后RDX/PMMA微球形貌趋于球形,RDX/PMMA/GO粒子存在明显的层状皱褶;RDX晶型均未发生改变;与原料RDX和RDX/PMMA相比,RDX/PMMA/GO微球的表观活化能分别提高22.16kJ/mol和15.17kJ/mol,升温速率趋近于0时的峰温和热爆炸临界温度与原料RDX相比分别提升6.45℃和6.23℃;特性落高由包覆前的26.74cm分别提至62.95cm和78.52cm,撞击感度明显降低。RDX/PMMA/GO抗压强度比RDX/PMMA增加了7.5MPa,表明GO的加入对复合材料的力学性能提升明显。     

撞击作用下螺压复合改性双基推进剂药片的响应

采用落锤仪研究了螺压复合改性双基(CMDB)推进剂药片在撞击作用下发生分解、燃烧或爆炸响应的临界值,获得了不同RDX含量、样品厚度及样品温度对推进剂在撞击作用下响应临界值的影响规律。结果表明,在推进剂中引入RDX不会增加推进剂对撞击刺激的敏感程度;RDX的质量分数为0~54.5%时,随着RDX含量的增加,推进剂药片对撞击刺激的敏感程度逐渐降低;样品厚度为1、2、3mm时,随着样品厚度的增加,推进剂药片对撞击刺激的敏感程度显著降低;推进剂在70℃时对撞击刺激比25℃时更加敏感。     

Production and Sensitivity Evaluation of Nanocrystalline RDX‐based Explosive Compositions

The initiation sensitivity of cyclotrimethylenetrinitramine (RDX) was investigated as a function of crystal size. For this study, RDX powders with mean crystal sizes of ca. 200 and 500 nm were prepared by rapid expansion of supercritical solutions (RESS) with carbon dioxide as the solvent. Initiation sensitivity testing to impact, sustained shock, and electrostatic discharge stimuli was performed on uncoated as well as wax‐coated specimens. The test data revealed that in a direct comparison to coarser grades the nanocrystalline RDX‐based samples were substantially less sensitive to shock and impact stimuli. Furthermore, the 500 nm RDX‐based specimens exhibited the lowest sensitivity values, an indication that minima in shock and impact sensitivities with respect to crystal size exist.     

Relationship Between RDX Properties and Sensitivity

An interlaboratory comparison of seven lots of commercially available RDX was conducted to determine what properties of the nitramine particles can be used to assess whether the RDX has relatively high or relatively low sensitivity. The materials chosen for the study were selected to give a range of HMX content, manufacturing process and reported shock sensitivity. The results of two different shock sensitivity tests conducted on a PBX made with the RDX lots in the study showed that there are measurable differences in the shock sensitivity of the PBXs, but the impact sensitivity for all of the lots is essentially the same. Impact sensitivity is not a good predictor of shock sensitivity for these types of RDX. Although most RDX that exhibits RS has low HMX content, that characteristic alone is not sufficient to guarantee low sensitivity. A range of additional analytical chemistry tests were conducted on the material; two of these (HPLC and DSC) are discussed within.     

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.     

Multiscale Simulation on the Influence of Dimethyl Hydantoin on Mechanical Properties of GAP/RDX Propellants

The influence of dimethyl hydantoin (DMH) on the mechanical properties of GAP/RDX propellant was studied by molecular dynamics (MD) and dissipative particle dynamics (DPD) simulation. The results showed that the binding energies (E_binding) between GAP and different surfaces of RDX were in the order of (010)>(001)>(100). Compared to GAP/RDX, GAP grafted with DMH (GAP‐DMH) exhibits higher binding energies with RDX, and the sequence of E_binding turns to (001)>(010)>(100). Radial distribution simulations demonstrated that GAP‐DMH is more close to the surfaces of RDX, increasing the van der Waals energies between GAP‐DMH and RDX. The stress and strain of GAP‐DMH/RDX excel those of GAP/RDX. DPD simulations showed that GAP‐DMH was able to restrain the agglomeration of RDX, to improve the dispersibility and to enlarge the contact surface with RDX, which also increased the mechanical properties of GAP/RDX propellant.     

Preparation and characterization of RDX based composite energetic materials with a cellulose matrix

Cyclotrimethylenetrinitramine (RDX)-based high-energy explosives are widely used in weapon warheads, propellants, and ammunition. Many studies have explored different supporting structures for RDX; however, the use of natural materials have rarely has been reported. Natural cellulose is widely known for its excellent compatibility and loading capacity. In this study, cellulose was used as a supporting structure and insensitive material for RDX composites. Cellulose/RDX composite aerogels (RCAs) were prepared using 1-allyl-3-methyl imidazole (AMIMCl) as the solvent, and their properties were characterized. The results show that the content of nitrogen in cellulose/RCAs was 34.5%, and the content of RDX was as high as 94.3%. Moreover, RDX particles were attached to the fibers inside the cellulose aerogels (CAs), forming a homogeneous protective layer on the surface of the cellulose matrix. Compared with the raw RDX material, the thermal stability of the cellulose/RDX energetic aerogels was greatly increased. The porosity of the CAs was reduced due to RDX particles growing inside the CAs. The impact sensitivity increased from 35 to 78 cm.