Stabilizer Depletion in Single Base Propellant from Unexploded Ordnance

Decomposition of nitrocellulose‐based propellant is a well‐known problem that results in insufficient shelf‐life of the ammunition if the propellant is not stabilized with appropriate materials. To investigate the influence of storage conditions on the shelf life of old propellant powder HPLC analytics according to AOP‐48 were carried out to determine the stabilizer consumption at different temperatures. The ingredients of the propellant were also analyzed. The results show that the examined propellant samples from WW II production are still containing stabilizer. Humidity in combination with elevated temperature seems to be the most influencing parameter for decomposition of this type. The analyzed propellants seem to be stable even after about 70 years under bad storage conditions. You might draw conclusions from these results for modern time propellant powders, which are stored under controlled conditions.     

Kinetic modelling of the stabilizer consumption and of the consecutive products of the stabilizer in a gun propellant

Diphenylamine is used for the stabilization of solid propellants based on nitrocellulose. It reacts with the autocatalyticly acting decomposition product of nitrocellulose and forms consecutive products, which also stabilize. The kinetics of these stabilizing reactions are described by four reaction models. With respect to DPA and the DPA consecutive products the models have one, two and four steps. The four step model contains the DPA consecutive products up to trinitro-DPA. By approximations an analytical equation for the stabilizer decrease could be derived, which describes the stabilizer consumption very well. The other equation systems have been integrated numerically by a Runge–Kutta procedure and their reaction rate constants have been obtained by a non-linear least squares fit parameter calculation. This allows an evaluation of the reaction kinetic models. Relative reactivities of the DPA consecutive products with respect to DPA are calculable with the obtained reaction rate constants and an effective DPA concentration can be established. The different reactivities of mixed stabilizers as MNA and 2-NO₂-DPA can be described with the presented method of modelling.     

Disposal of Energetic Materials by Alkaline Pressure Hydrolysis and combined techniques

Due to the reduction of armament and especially due to the German reunification we are met by the objective of the disposal of energetic materials. Environmentally friendly disposal methods available for the different propellants, explosives and pyrotechnics are urgently needed. The main component of gun and rocket propellants is the energetic polymer nitrocellulose. One method to dispose nitrocellulose containing propellants is the combination of rapid chemical destruction by pressure hydrolysis and the biological degradation of the reaction mixture. The study describes the results of pressure hydrolysis of different gun and rocket propellants. Under alkaline conditions (propellant to NaOH ratio 2.3:1; reaction temperature 150 °C; pressure below 30 bar) biological degradable reaction products were formed. The main products in the liquid phase were simple mono- and dicarboxylic acids. Dependent on the reaction conditions 30–50 % of the nitrogen content of the propellants was transformed to nitrite and nitrate. The gaseous nitrogen containing products were N₂ (16–46 %), N₂O (2–23 %), NO_x (0–5 %). Overall 40%–60% of the propellant nitrogen was transformed to gaseous products. In the solid residues a nitrogen content between 2 % and 9 % was found. The residues were mostly due to additives used in propellant manufacturing. In the case of nitrocellulose pressure hydrolysis below 30 bar and reaction temperature about 150 °C are sufficient.     

Formulation and Characterization of a New Nitroglycerin‐Free Double Base Propellant

Double base propellants composed of nitrocellulose (NC) and nitroglycerine (NG) are widely used. However, the inclusion of liquid NG presents both stability and performance problems: the NG may migrate from the propellant in storage, and it softens the propellant at high inclusion levels. In this work, the novel nitrate ester 1,4‐dinitrato‐2,3‐dinitro‐2,3bis(nitratomethylene) butane (SMX) is considered as a replacement for NG in a double base propellant. Thermochemical calculations indicate improved performance when compared with the common double base propellant JA2 at SMX loadings above 40 wt‐%. Also, since SMX is a room temperature solid, migration may be mitigated. Both unplasticized and plasticized propellants were formulated to enable the study of the interaction of SMX with nitrocellulose. Thermal analysis of unplasticized propellant showed a distinct melt‐recrystallization curve, which indicates that a solid phase solution is being formed between SMX and NC, and that SMX would not act as plasticizer. Analysis of propellant prepared with diethyleneglycol dinitrate (DEGDN) plasticizer indicates that the SMX is likely dissolved in the DEGDN. The plasticized material also showed similar hardness and modulus to JA2. Safety characterization showed that sensitivity is similar to JA2. In short, replacing NG with SMX results in a new family of propellants with acceptable safety characteristics and which may also offer improved theoretical performance.     

Sensitivity of Solid Rocket Propellants for Card Gap Test

Card gap test, which is standardized in Japan Explosives Society, was modified in order to apply it to solid rocket propellants and carried out to evaluate sensitivities against shock stimuli. Solid propellants tested here were mainly azide polymer composite propellants, which contained ammonium nitrate (AN) as a main oxidizer. Double base propellant, composed nitroglycerin and nitrocellulose (NC), and ammonium perchlorate (AP)-based composite propellants were also evaluated in order to compare with the azide polymer propellants. It is found that the sensitivity was dominated by the oxidizer characteristics. AP-and AN-based propellant had less sensitivity and HMX-based propellant showed higher sensitivity, and the adding of NC and TMETN were contributed to worse sensitive for the card gap test. Good relationship was obtained between the card gap sensitivity and the oxygen balance of propellants tested here.     

Investigation of the Decomposition Mechanism and Thermal Stability of Nitrocellulose/Nitroglycerine Based Propellants by Electron Spin Resonance

Nitrocellulose based (NC) and nitroglycerin based (NG) propellants often have a fixed acid and water content during the manufacturing time. After manufacture, the quantity and ratio of acid/water will continue to vary depending upon the conditions of storage and operation. The level of variation depends on many factors such as loading density, temperature, volume of ullage and sealing condition of the containing cartridge, just to name a few. As described in this paper and other literature, the degradation mechanisms and aging processes of NC/NG based propellants are extremely complicated. This paper describes the details of the application of Electron Spin Resonance (ESR) to study if the free‐radical mechanism is involved in the decomposition of nitrocellulose and nitroglycerin. Due to the high free‐radical intensity possessed by the propellant composition, we believe that a π complex intermediate may be formed between DPA and NG and/or NC. The formation of a π complex intermediate is not preferred because it may enhance the rate of decomposition of nitrate esters.     

含高氮化合物的高燃速CMDB推进剂的能量特性

利用能量计算程序计算了含高氮化合物3,6–双(1–氢–1,2,3,4–四唑–5–氨基)–1,2,4,5–四嗪(BTATz)的复合改性双基(CMDB)推进剂的能量特性,并研究了用3种含能添加剂高氯酸铵(AP)、六硝基六氮杂异伍兹烷(HNIW)、黑索今(RDX)和2种增塑剂1,5–二叠氮基–3–硝基–3–氮杂戊烷(DIANP)及二缩三乙二醇二硝酸酯(TEGDN)分别部分取代BTATz和硝化甘油(NG)后,对含BTATz的CMDB推进剂能量特性的影响规律。结果表明:无论推进剂中是否含铝粉,用BTATz取代CMDB推进剂中的硝化棉(NC)和NG后,将不同程度地降低原推进剂的各能量特性参数;用AP和HNIW部分取代BTATz后,可使BTATz–CMDB推进剂的理论比冲明显提高;用DIANP或TEGDN部分取代推进剂中的NG,各能量特性参数均随其含量增加而减小。     

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.     

A Desorption Electrospray Ionization Mass Spectrometry Study of Aging Products of Diphenylamine Stabilizer in Double‐Base Propellants

Double‐base propellants consisting of nitrocellulose, nitroglycerin and stabilizer undergo chemical and physical changes upon aging, leading to changes in ballistic power and presenting explosive hazards. During aging, PTFE seals of the glass ampoules used in the aging studies undergo a yellow discoloration. This report studies the discoloration of the liners using desorption electrospray ionization (DESI), a gentle surface analysis technique based on electrospray ionization. The color bodies in the PTFE liners were identified by DESI together with tandem mass spectrometry to be the nitrated derivatives of the diphenylamine stabilizer: dinitro‐, trinitro‐, and tetranitrodiphenylamine. While increased nitration decreases vapor pressure of the DPA species, an increase in solubility in the PTFE liners occurs. This may account for these species not previously being observed during early aging studies as they are preferentially absorbed into the liners, which were not extracted prior to high performance liquid‐ chromatography analysis.     

An Efficient Method for Determination of the Diphenylamine (Stabilizer) in Propellants by Molecularly Imprinted Polymer based Carbon Paste Electrochemical Sensor

In this work we report efficient molecularly imprinted polymer (MIP) based carbon paste electrode sensor for the determination of diphenylamine in aged propellant. Initially, diphenylamine (DPA)‐MIP was synthesized by using methacrylic acid (monomer) and ethylene glycol dimethyacrylate (cross‐linker). Developed DPA‐MIP was analyzed by Fourier transform infrared spectroscopy and Field‐emission scanning electron microscopy. The sensor was incorporated as electrode in cyclic voltammetry. The sensor response was linear in the range of 0.5–3 mM DPA concentration. The lower detection limit obtained for sensor was 0.1 mM. The developed sensor was used for the determination of DPA in propellant systems. Same electrode was used for three repeated analysis without significant decrease in efficiency.     

Burning Rates and Thermal Behavior of Bistetrazole Containing Gun Propellants

The influence of two selected bistetrazoles, 5,5′‐bis(1H‐tetrazolyl)‐amine (BTA) and 5,5′‐hydrazinebistetrazole (HBT), on the combustion behavior of a typical triple‐base propellant was investigated. Seven propellant formulations, one reference and six others incorporating 5 %, 15 %, and 25 % of either HBT or BTA compounds, respectively, were mixed and extruded into a cylindrical, no perforations, geometry. The resulting propellants showed high burning rates, up to 93 % higher than the reference formulation at 100 MPa. However, the increase in burning rates came at the cost of higher burning rate dependency on pressure, with a pressure exponent as high as 1.4 for certain formulations. HBT‐containing propellants showed notably lower flame temperature when compared to the reference formulation, with a flame temperature reduction of up to 461 K for the propellant containing 25 % HBT. The thermal behavior of the propellants was also investigated through DSC experiments. The addition of bistetrazoles provided lower decomposition temperatures than the pure nitrogen‐rich materials, indicating that the two compounds probably react readily with the −ONO₂ groups present in the nitrocellulose and the plasticizers used in the formulation. The onset temperature of all propellants remained within acceptable ranges despite the observed decrease caused by the addition of the bistetrazole compounds.     

Preliminary Study of New Propellants Containing Guanidinium or Triaminoguanidinium Azotetrazolate

Guanidinium and triaminoguanidinium azotetrazolate (GUAZ, TAGAZ) were used as high‐nitrogen compounds for the preparation of new propellants bound with nitrocellulose and plasticized with dibutyl phthalate and 3‐methyl‐3‐nitroxymethyloxetane. The new propellant compositions were tested by using a differential thermal analysis‐thermogravimetric technique, friction sensitivity and impact were ascertained and pyrostatic tests were conducted. Regardless of the amount of TAGAZ and plasticizer type, the propellants exhibit similar maximum pressure of the gases which allow for the replacement of NC in propellants by TAGAZ.     

Studies on RDX Particle Size in LOVA Gun Propellant Formulations

This paper presents the results of systematic studies carried out on the role of fine RDX in determining the burning rate and ballistics of LOVA gun propellants. Propellant formulations containing fine RDX particles with a size of 4.5, 6, 13 and 32 µm as energetic ingredient, cellulose acetate as inert binder, triacetin as inert plasticizer, nitrocellulose of lower percentage nitrogen content as energetic binder and carbamite as stabilizer were made. The evaluation of the propellant batches has been carried out by static firing using closed vessel technique. It indicates the linear relation between the burning rate of the propellant and the fine RDX particle size used in this formulation. The results of the present studies revealed that fine RDX of 4.5 to 6 µm size may be the most suitable for LOVA gun propellant to meet the desired burning rate for satisfactory ballistics.     

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.     

含FOX-7发射药的燃烧性能

采用常规密闭爆发器研究了含FOX-7硝胺发射药的燃速、压强指数和压强变化率。结果表明,随着样品中FOX-7含量的增加,发射药的点火延滞时间增加,燃速系数减小,燃速降低;其压强变化率的最大值及增长速率均降低。当燃烧压强小于150MPa时,FOX-7含量对发射药的压强指数没有影响,FOX-7改善发射药压强指数的能力不明显;随着燃烧压强的增加,含FOX-7发射药的压强指数降低,尤其当燃烧压强大于200MPa时,发射药的燃速压强指数显著降低。随着发射药中FOX-7含量的增加,其压强指数及燃速系数均降低,有利于发射药的稳定燃烧。     

Temperature profile in the combustion wave of low calorific value propellants

Combustion wave temperature profiles are determined for two low calorific value propellants (Q _c = 2189 and 2518 kJ/kg). It is shown that the structure and parameters of the combustion wave differ significantly from those for previously studied propellants of medium (propellant N) and high (propellant NB) calorific values. At a relatively short distance from the burning surface, the temperature is significantly (180–270 K) higher than the calculated value due to fact the combustion products contain carbon black from the decomposition of heat-resistant dibutyl dinitrotoluene and dibutyl phthalate. Then, part of carbon black reacts endothermically with CO₂ and H₂O, leading to a decrease in temperature, which for the first sample is nevertheless 100–140 K higher than the thermodynamic value. For the investigated propellants, the activation energy of the leading reaction is the same as for the previously studied propellants, suggesting a common decomposition kinetics of the condensed phase regardless of the propellant composition. However, a uniform dependence of the burning rate on surface temperature is not observed. For low calorific value propellants, the surface temperatures are close to those for propellant N although their burning rate is significantly (2–2.2 times) lower. The causes of this fact are considered.     

Analysis of Stabilizer Degradation Products in Propellants Using HPLC and Photodiode Array(PDA) Detection

Analysis of stabilizer and stabilizer degradation products in nitrocellulose based propellants was done using high-performance liquid chromatography(HPLC) with photodiode array(PDA) detection. Analysis of these compounds was done in less than 12 minutes using an isocratic mobile phase. Using PDA detection provided the capability of monitoring at several different wavelengths as well as providing UV spectra which could be used to assess peak purity and match the spectra against known library spectra.     

室温固化催化剂的研制和在固体推进剂中的应用

研制了 3种有机金属化合物TEPB p、TEPB m和TEPB o,均为白色结晶 ,纯度 >99.0 %。通过热分析方法、推进剂配方工艺研究与性能测试 ,探讨了它们对NEPE和丁羟固体推进剂固化反应的催化作用。结果表明 ,其催化活性高 ,能降低固化反应温度 ,能使推进剂药浆在室温 (35℃或 35～ 4 0℃ )保温 7～ 8d完全固化 ,并使获得的推进剂具有良好力学性能 ,因而它们可用作室温固化催化剂。     

多基发射药燃烧性能的调节与优化

介绍了近来提出的多基发射药燃烧模型，利用其计算方法计算了多基发射药的化学组成对燃烧性能的影响；从化学结构和化学反应的层次分析了硝胺发射药燃速－压力曲线转折和某一压力范围内压力指数大于１的原因；从化学组成的角度出发提出了多基发射药燃烧性能优化设计的一些基本原则。     

双基发射药和混合硝酸酯发射药的热分解特性

采用C80微热量仪分析了等容条件下初始药量对双基发射药和混合硝酸酯发射药热分解性能的影响.结果表明,随着初始药量的增大,双基发射药的反应放热峰向低温方向移动,混合硝酸酯发射药的反应放热峰位置基本不变;双基发射药单位质量发热量和反应活化能均呈逐渐降低趋势,而混合硝酸酯发射药单位质量发热量和反应活化能保持在一较小范围内基本不变.这种差异由混合硝酸酯发射药中二缩三乙二醇二硝酸酯(TEGDN)分解产生的过量甲醛引起.