TEGDN含量和NC含氮量对TEGDN/NG混合酯双基推进剂力学性能的影响

采用无溶剂法制备了24种不同硝化三乙二醇(TEGDN)含量、不同NC含氮量的双基推进剂样品,并测试了其高温(50℃)、常温(20℃)和低温(-40℃)下的力学性能;讨论了TEGDN含量和NC含氮量对双基推进剂力学性能的影响。结果表明,混合酯双基推进剂的高温和常温抗拉强度随TEGDN含量增加而逐渐下降,在TEGDN质量分数较低(≤7.7%)时,随NC含氮量的升高呈降低趋势,在TEGDN质量分数较高(≥15.4%)时,随NC含氮量的升高呈先上升后下降的趋势;低温抗拉强度随TEGDN含量增加而逐渐升高,随NC含氮量的升高逐渐降低;高温、常温、低温下的断裂延伸率均随TEGDN含量增加逐渐上升,随NC含氮量的升高逐渐下降;提高TEGDN含量可以改善NC的塑化性能,但含氮量12.6%及以上的NC不易被良好塑化。     

低温感发射药包覆层的力学性能

针对现有太根包覆发射药,研究了其内外包覆层在不同温度下的力学性能。通过拉伸、压缩和冲击试验,探讨了内外包覆层力学性能的差异,并通过中止燃烧试验,得出实际太根包覆药在不同温度下的破孔规律。研究发现,太根药内外包覆层的力学性能受温度影响较大,可利用这一特性来制造低温感包覆药。加入阻燃剂二氧化钛后,包覆层的力学性能降低,但在不同温度下的变化趋势不变,不会对包覆药的整体效果造成不利影响。     

催化剂对太根发射药燃速的影响

为探讨调节发射药燃气生成规律的途径,采用催化剂调节太根发射药的燃速,通过密闭爆发器实验测试了不同催化剂对太根发射药燃速调节的效果。结果表明,使用催化剂可以有效调节太根发射药的燃速,当测试压力为50~150M Pa时,碳酸镍可使太根发射药的燃速提高8%以上,二茂铁可使太根发射药的燃速降低10%。所研究的6种催化剂对发射药燃速压力指数的影响均小于0.02。     

Preparation and Properties of a nRDX‐based Propellant

The incorporation of nano‐scaled cyclotrimethylene trinitramine (nRDX) in nitrocellulose (NC)‐based propellants poses processing problems when following conventional methods. Hence, a new preparation method containing a pre‐dispersion process was developed, by which 30 mass % RDX (290 nm) was incorporated in the propellant. Meanwhile, the corresponding 290 nm, 12.85 μm and 97.76 μm RDX‐based propellants were prepared for comparison using a conventional method. The morphology, structure, ballistic and mechanical properties of the prepared propellants were characterized by scanning electron microscopy (SEM), density analyzer, closed vessel (CV), uniaxial tensile tester and impact tester. The results indicate that the nRDX particles were uniformly dispersed in the NC/NG/TEGDN matrix using the novel method, while agglomerated and recrystallized into large particles with the conventional method. The propellant density increased with decreasing RDX particle size. In particular, the 290 nm RDX‐based propellant exhibited a higher burning rate and lower average pressure exponent (α =0.958) compared to the 12.85 μm RDX‐based propellant (α =1.043). The tensile strength, elongation at break and impact strength of the RDX‐based propellant at −40 °C, 20 °C and 50 °C were dramatically improved by using 290 nm RDX with the novel method.     

Guidelines for dryer design based on results from non‐Fickian model

In polymer solution coatings below the glass transition temperature of the pure polymer, the coating can go undergo a glass transition and develop stresses during drying. When stresses develop, a non‐Fickian model accurately describes solvent mass transport in drying polymer coatings. The non‐Fickian model includes the solvent transport due to both stress and concentration gradients. This article presents a non‐Fickian model, which predicts a lower residual solvent than does the corresponding Fickian model. We showed in an earlier article that the non‐Fickian model predicts trapping skinning (higher residual solvent under more intense operating conditions) at higher drying gas‐flow rates. In this article, the non‐Fickian model was used to investigate how the gas‐flow rate, dry film thickness, and substrate thickness affect the residual solvent for a single‐zone dryer. This work recommends guidelines for choosing gas‐flow rates, gas temperatures, and substrate thickness to minimize the residual solvent. The model predictions show that, at any gas temperature, the residual solvent is minimum at an intermediate gas‐flow rate. The trapping skinning effect is less evident in thicker coatings and substrates. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 477–486, 2003     

燃烧催化剂对太根发射药燃烧性能的影响

将燃烧催化剂引入太根发射药中,利用密闭爆发器静态燃烧实验研究了这些燃烧催化剂对太根发射药燃烧性能的作用效果.结果表明,某些特殊的燃烧催化剂,可较好地降低该类发射药局部燃烧压强范围内的燃速压强指数,降低压强指数的压力范围与所用催化剂的种类有关.研究还发现,邻苯二甲酸铅有缩短太根发射药燃烧时间、提高燃烧速度、增加气体生成猛度的作用;含铜金属盐有抑制太根发射药燃气生成猛度的作用.     

LOVA Propellant Aging: Effect of Residual Solvent

An investigation of LOVA propellant aging was performed to identify the cause of stabilization periods in certain propellant lots. Two important observations were made: (1) the level of residual solvent in propellant grains slowly decrease while in storage, and (2) during the drying process and while the grains are in storage, plasticizer “co-migrates” with solvent, resulting in plasticizer accumulation at grain surfaces. It was also observed that while in storage, residual solvent may be oxidized to generate organic acids. Based on these results, it is proposed that stabilization periods result from processes related to migration, evaporation, and oxidation of residual solvent.     

Preparation and Characteristics of Foamed NC‐Based Propellants

Foaming properties of the three NC‐based (nitrocellulose‐based) propellants, namely, single‐base propellant, NG (nitroglycerine) propellant and TEGDN (triethylene glycol dinitrate) propellant were investigated in the batch foaming process by using supercritical CO₂ as the physical foaming agent. Burning characteristics of the foamed NC‐based propellants were also investigated in this work. For this study, the CO₂ desorption of the three NC‐based propellants were plotted by the gravimetric method. The morphology and burning characteristics of these foamed NC‐based propellants were characterized by scanning electron microscope (SEM) and closed vessel experiment. The test data revealed that the energetic plasticizer has a considerable effect on the pore formation in the NC matrix although it has little effect on the CO₂ solubility in the NC‐based propellants. Moreover, the SEM images showed the foaming temperature also plays an important role in the pore parameters of foamed propellants. Furthermore, the data of closed vessel experiment indicated that the burning characteristics of foamed NC‐based propellants largely depend on the pore parameters, and the porous structure of foamed propellants would considerably increase the mass conversion rate.     

过渡金属有机酸盐M对太根发射药燃速压力指数的影响

将过渡金属有机酸盐M作为催化剂引入太根发射药中,通过密闭爆发器实验测试了催化剂M对太根发射药燃速压力指数降低的效果,并利用发射药能量示性数软件计算了含催化剂M的太根发射药的火药力和爆温。结果表明,合适的催化剂M含量可以降低测试压力范围内太根发射药的燃速压力指数,添加质量分数为1.5%的催化剂对太根发射药燃速压力指数的降低作用最明显,此时火药力下降不到1%,对发射药能量影响较小。     

Solvent screening for non‐aqueous extraction of Alberta oil sands

Non‐aqueous extraction of bitumen from oil sands has the potential to reduce fresh water demand of the extraction process and eliminate tailings ponds. In this study, different light hydrocarbon solvents, including aromatics, cycloalkanes, biologically derived solvents and mixtures of solvents were compared for extraction of bitumen from Alberta oil sands at room temperature and ambient pressure. The solvents are compared based on bitumen recovery, the amount of residual solvent in the extracted oil sands tailings and the content of fine solids in the extracted bitumen. The extraction experiments were carried out in a multistage process with agitation in rotary mixers and vibration sieving. The oil sands tailings were dried under ambient conditions, and their residual solvent contents were measured by a purge and trap system followed by gas chromatography. The elemental compositions of the extraction tailings were measured to calculate bitumen recovery. Supernatants from the extraction tests were centrifuged to separate and measure the contents of fine solid particles. Except for limonene and isoprene, the tested solvents showed good bitumen recoveries of around 95%. The solvent drying rates and residual solvent contents in the extracted oil sands tailings correlated to solvent vapour pressure. The contents of fine solids in the extracted bitumen (supernatant) were below 2.9% for all solvents except n‐heptane‐rich ones. Based on these findings, cyclohexane is the best candidate solvent for bitumen extraction, with 94.4% bitumen recovery, 5 mg of residual solvent per kilogram of extraction tailings and 1.4 wt% fine solids in the recovered bitumen. © 2012 Canadian Society for Chemical Engineering     

Optimization of single‐zone drying of polymer solution coatings using mathematical modeling

Optimal conditions for drying polymer–solvent coatings result from a trade‐off between minimizing the residual solvent level and creating defects. This article describes an application of automated constrained optimization with a detailed mathematical drying model to find the optimal drying conditions for a prototypical coating in a single‐zone oven. The optimization process seeks oven conditions that minimize the residual solvent level for a fixed oven residence time without boiling the solvent within the coating. The optimal oven conditions include the air temperature and coating‐side and substrate‐side heat‐transfer coefficients. The conditions are constrained to physically reasonable values. According to our results, the optimal coating‐side heat‐transfer coefficient is always equal to or greater than the optimal substrate‐side heat‐transfer coefficient. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 149–165, 2000     

铝含量和含氟有机化合物对丁羟推进剂燃烧性能的影响

为进一步提高HTPB推进剂的能量并抑制铝粉在燃烧过程中的团聚,制备了铝粉质量分数为16%~22%的端羟基聚丁二烯(HTPB)推进剂,并分别加入含氟有机化合物(OF)作为铝燃烧促进剂,研究了铝含量和OF对HTPB推进剂燃烧性能的影响;使用氧弹量热仪测定了推进剂在氩气氛围下(3 MPa)的爆热;收集在3 MPa下推进剂燃烧的凝聚相产物,采用激光粒度仪、X射线光电子能谱仪(XPS)及X射线衍射仪(XRD)等分别对其进行粒度分布、元素和物相分析;通过线扫描摄像机和高压燃烧室系统测定推进剂的燃速;利用高速摄影系统观察推进剂燃面上熔铝粒子的团聚过程。结果表明,HTPB推进剂在铝粉质量分数为20%时实测爆热最大,含氟有机物OF的引入使得爆热有所下降;随着HTPB推进剂中铝含量的提高,燃面上熔铝粒子的团聚愈加严重,凝聚相燃烧产物的尺寸和残留铝含量均逐渐增加;加入含氟有机物OF能够促使-Al2O3和AlF3的生成,有效抑制铝颗粒在燃烧过程中的团聚,使凝聚相燃烧产物的尺寸和残留铝含量显著降低,当铝粉质量分数为20%时,OF的加入使得残留铝的生成率降低了50%;较低的铝含量和OF的添加有利于HTPB推进剂燃速的提高。     

Effects of an Organic‐inorganic Nanocomposite Additive on the Combustion and Erosion Performance of High Energy Propellants Containing RDX

A nanocomposite microsphere consisting of solid paraffin, nano‐TiO₂, nano‐BN, zeolitic imidazolate framework‐67 particles and polymethyl methacrylate was prepared and applied as a functional additive for high energy propellants (with about 23 wt % RDX) to reduce the barrel erosion and improve its combustion performance as well. High energy propellants modified with the nanocomposite were manufactured by a solvent extrusion technique. According to the scanning electron microscope and differential scanning calorimetry results, there exists a good compatibility between the nanocomposite and propellant matrix. The energy and combustion performance as well as erosion of the modified propellants were studied by a closed bomb test and an erosion tube device, respectively. Results showed that compared with the unmodified propellant, both the erosion and energy performance of modified high energy propellant gradually decreased with the increase of nanocomposites contents. When the content of nanocomposites was 5.1 %, the erosion mass of the modified propellant reduced to 37.0 % while the propellant force only decreased 5.7 %, indicating that the nanocomposite has enormous ability to improve gun erosion resistance while barely affect energy performance of propellant. Furthermore, the closed bomb burning curves of the samples showed that addition of nanocomposites to propellant matrix could prolong the combustion time, efficiently inhibit the initial generation rate of combustion gas, and further achieve the progressive burning of the propellants.     

1,5-二叠氮基-3-硝基氮杂戊烷对硝化棉的溶塑作用

采用双滚筒炼胶压延机、扫描电镜、材料试验机等试验对比分析了叠氮硝胺发射药和双基发射药无溶剂法制备的工艺性能、发射药内部形貌、发射药静态力学性能等.结果表明,对于含氮量(质量分数)分别为12.6%、J3.0%的高氮量硝化棉,叠氮硝胺发射药比双基发射药的压延塑化温度、塑化遍数、成型压力均较低.1,5-二叠氮基-3-硝基氮杂...     

Mechanical and electrical properties of poly(vinylidene fluoride–tetrafluoroethylene–propylene)/Super‐S carbon black swelled in liquid solvent as an electrode binder for lithium‐ion batteries

The mechanical and electrical properties of poly(vinylidene fluoride–tetrafluoroethylene–propylene) (PVDF–TFE–P) and carbon black–filled PVDF–TFE–P composites were investigated. The carbon black was used for its electrolyte absorption properties in addition to boosting the conductivity. This elastomeric binder system may have application to tin‐ or silicon‐based electrode materials for Li‐ion batteries, which undergo huge volumetric changes during charge/discharge cycling. The mechanical and electrical properties were measured while film samples were immersed in a liquid solvent (ethylene carbonate : diethyl carbonate 1 : 2) commonly used in the battery electrolyte. Uncrosslinked PVDF–TFE–P uptakes about 140% solvent by mass and swells significantly. The amount of solvent absorbed can be reduced and the mechanical properties improved by crosslinking the polymer. Two crosslinking recipes, based on bisphenol and triethylenetetramine (TETA), were investigated carefully. Compared to the bisphenol‐based crosslinking recipe, the proposed TETA‐based crosslinking recipe gave films with a higher degree of crosslinking and better mechanical properties. The TETA‐crosslinked composites had very good mechanical and electrical reversibility even during cyclic deformation to 100% strain. The cycling results of amorphous Si_0.64Sn_0.36 electrodes show that the capacity retention of the electrodes can be significantly improved by using the proposed elastomeric binder. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2958–2965, 2004     

Isocyanate‐Free Curing of Glycidyl Azide Polymer with Bis–propargylhydroquinone

Bis‐propargylhydroquinone (BPHQ) is an alkyne functionalized isocyanate‐free curing agent for hydroxyl terminated azido polymers. Conventionally, glycidyl azide polymer (GAP) is cured by isocyanate based curatives, which are toxic and hygroscopic in nature. The reaction between hydroxyl end group of GAP and isocyanate is highly sensitive to moisture causing voids in the propellant, leading to poor mechanical properties. Herein, an alternate approach was adapted to exploit 1,3‐dipolar cycloaddition reaction between azido group of GAP and the triple bond (–C≡CH) of BPHQ without catalyst at 50 °C forming triazole crosslinked polymer. The curing behavior of GAP‐BPHQ system was studied by rheological method and based on the results the gel time was determined. In addition, the reaction between GAP and BPHQ was carried out with various GAP/BPHQ ratios (0.9 to 2.5) and effects on mechanical properties of resulting triazole polymers were investigated. Post curing hardness of GAP‐BPHQ binder system was tested by surface Shore‐A hardness measurement. The compatibility of BPHQ with energetic oxidizers such as ammonium dinitramide (ADN) and hydrazinium nitroformate (HNF) were also studied by differential scanning calorimetery (DSC) technique and showed good compatibility. The activation energy (E _a) of cured GAP‐BPHQ binder was evaluated by DSC using Ozawa and Kissinger methods and are found to be 33.55 and 33.16 kcal mol^–1, respectively. The advantage of this curing system between GAP and BPHQ is unaffected by moisture as compared to isocyanate based urethane systems and also no need to control humidity during the processing of propellant. The experimental results reveal that triazole crosslinked polymer system could be a better choice to develop novel energetic binder systems for explosives as well as propellants composition with improved performance and eco‐friendly nature.     

Response of TEGDN Propellants to Plasma Ignition with the Same Magnitude of Ignition Energy as Conventional Igniters in an Interrupted Burning Simulator

In order to consider the potential influence of ignition energy factors on the response of double base propellants plasticized with triethyleneglycol dinitrate (TEGDN propellants), the influence of different ignition methods at the same magnitude of ignition energy level on the response of TEGDN propellants was investigated in an interrupted burning simulator. Compared to conventional ignition methods, plasma ignition exhibits a significantly shorter ignition delay and lower ignition energy. There are stronger ablation and impact interactions of plasma flow with the surface of propellants. For TEGDN propellants coated with titanium dioxide, a greater amount of melted white layer is deposited on the surface of propellants. The content of copper on the surface of recovered plasma‐ignited samples observed by X‐ray Fluorescence (XRF) spectroscopy is much larger than that on the surface of recovered conventionally ignited samples, indicating more deposition of copper wire discharge on the surface of the samples. The test results will benefit the design of plasma generator and electrical parameters of pulse power to satisfy certain propellant compositions.     

Spatially resolved drying kinetics of multi-component solution cast films for organic electronics

The use of multi-component solvent/additive systems can be beneficial in the manufacturing process of organic and printed electronics because they can provide an extended degree of freedom, in terms of optimized wetting properties or their influence on the molecular ordering during solvent evaporation. For a systematic investigation of the drying process of such systems a technique for the measurement of the evaporation kinetics for micrometer to nanometer thin films is required. Since large area films are drying faster at the edges, we determine the drying kinetics spatially resolved in a linear array of 5 reflectometers simultaneously for single and binary solvent systems for polymer–fullerene (P3HT:PCBM) solutions as used in organic photovoltaic.In order to design a specific drying process, e.g. combined fast and slow evaporation of high or less solving solvents, a spatial resolved numerical investigation of solvent mass transfer is addressed. A numerical approach including the effect of a moving drying front shows reasonable agreement for single and binary solvent systems with spatially resolved experimental data. The effect of the moving drying front accelerates the drying kinetics at a distinct position as the front approaches and must also be considered for integral measurements (e.g. gravimetric experiments).     

Effect of Coating of Ammonium Perchlorate with Fluorocarbon on Ballistic and Sensitivity Properties of AP/Al/HTPB Propellant

Fluorocarbon polymers are used to enhance thermal stability and electrostatic protection of composite propellant compositions. A precipitation technique has been developed to coat ammonium perchlorate (AP) using a copolymer of hexafluoropropylene and vinylidene fluoride (HFP‐VF) with the help of solvent‐counter solvent method. The coated AP has been used to prepare propellant compositions in different ratio based on hydroxyl terminated polybutadiene (HTPB), aluminium powder along with uncoated AP and studied for viscosity build‐up and visco‐elastic behaviour as well as mechanical, ballistic, thermal and sensitivity properties keeping 86% solid loading. The data on viscosity build‐up indicate that as the percentage of viton coated AP increases end of mix viscosity and viscosity build‐up increase accordingly. The mechanical properties data reveal that tensile strength and percentage elongation are found in increasing order. The burn rate of the composition also increases on higher percentage of HFP‐VF coated AP. The thermal stability of composition increases as the percentage of HFP‐VF coated AP increases. The data on sensitivity indicate that impact sensitivity decreases on increasing the percentage of HFP‐VF coated AP while no change is observed in friction sensitivity value.     

大颗粒球形发射药的制备及性能测试

为了解决现有球形发射药制备中存在的溶剂用量大、粒径不均一的问题,以双基吸收药为原料,采用剪切搓圆法制备大颗粒球形发射药。研究了溶棉质量比、搓丸刀间距、丸条直径对球形药质量的影响,采用密闭爆发器试验对成型、干燥后的样品进行了定容燃烧性能测试。结果表明,当溶棉质量比为0.4∶1.0、搓刀间距为0.4mm、丸条直径为3.8mm时,可得到粒径均一的球形颗粒,烘干后球形颗粒伸长度为1.033,颗粒密度可达1.680g/cm~3,堆积密度可达0.945g/cm~3,与内溶法制备的球形药的密度相当,密闭爆发器实验所得曲线表明制备的球形颗粒燃烧过程稳定,呈减面性。