Triphenylamine – a ‘New’ Stabilizer for Nitrocellulose Based Propellants – Part I: Chemical Stability Studies

Triphenylamine (TPA) was used for the first time in France in 1937 as a stabilizer for propellants. The stability of those samples was described as ‘good’. Around 1950 an American group produced TPA stabilized propellants and investigated the decomposition mechanism. Apart from one single experiment in the 1970s no further attempts were made to take TPA as a stabilizer for propellants.     

Study of the Effects of Aging under Humidity Control on the Thermal Decomposition of NC/NG/BTTN/RDX Propellants

The effects of aging under controlled humidity on the thermal decomposition of two nitrate ester/RDX propellants are examined. Propellant samples are artificially aged at 60 °C and 70 °C at various levels of relative humidity. Differential scanning calorimetry is used to study the post aged samples to determine the activation energy of the peak exotherm and peak temperature of these events. For each humidity level, differential scanning calorimetry is conducted on an aged and an unaged sample that is conditioned to the humidity of the environment to distinguish between aging effects and residual moisture effects. Nitrate ester stabilizer depletions rates are presented as a function of aging and humidity. The results of the study show that moisture level during aging irreversibly alters the activation energy of the primary heat release events and significantly influences the stabilizer depletion rates.     

Effects of Organic Sulfur and Phosphor Compounds Used as Antioxidants on the Thermal Behavior of Nitrocellulose and its Decomposition Mechanism

The effects of 3‐dodecylsulfanyl‐propionic acid 3‐(3‐dodecylsulfanyl‐propionyloxy)‐2,2‐bis‐(3‐dodecylsulfanyl‐propionyl‐oxymethyl)‐propyl ester (SO), 3,9‐bis‐octadecyloxy‐2,4,8,10‐tetraoxa‐3,9‐diphospha‐spiro[5,5]undecane (POf), and 3,9‐bis‐(2,6‐di‐tert‐butyl‐4‐methyl‐phenoxy)‐2,4,8,10‐tetraoxa‐3,9‐diphospha‐spiro[5,5]undecane (POp), which are used as antioxidants for polymers, on the degradation of nitrocellulose (NC) were investigated under isothermal storage conditions at 393 K with a microcalorimeter. The result indicated that SO/NC and POf/NC accelerated the heat release when compared with NC without an antioxidant, whereas the heat release behavior of NC/POp was similar to that of NC without an antioxidant. In the case of SO/NC and POf/NC, the heat release was observed in the presence of O₂, whereas it was not observed in a N₂ atmosphere. The SO content in SO/NC and PO content in POf/NC increased with the storage time. According to this behavior, it can be explained that sulfuric acid or phosphoric acid, which originates from SO or POf, accelerates the autoxidation of NC.     

火药热分解特性与燃烧稳定性间相关性的分析

火药热分解过程的复杂性与其燃烧稳定性之间,存在有某种统计性的增函数关系。火药热分解特性对其燃烧特性的影响,是通过燃烧过程中亚表面热分解表观活化能的变化来实现的,当环境温度和压力较低时,亚表面的热分解特性,与常规条件下该火药的热分析结果相近。对于热分解过程较为复杂的火药,随着环境压力和温度的升高,其亚表面的分期机理和表观分解活化能将发生改变,亚表面分解速率随压力的变化规律也要发生变化,这就导致了燃烧过程的不稳定性,而对于那些热分解过程较为简单的火药,则不会出现这种情况,此外,本文还提出,火药中某些组分的爆燃是导致一些火药燃速压力指数较高的原因。     

Fragmentation of Fluorinated Model Compounds Exposed to Oxygen Radicals: Spin Trapping ESR Experiments and Implications for the Behaviour of Proton Exchange Membranes Used in Fuel Cells

Low‐molecular weight model compounds (MCs) for Nafion membranes used in fuel cells were exposed at 300 K to ^·OH radicals produced by UV irradiation of aqueous H₂O₂ solutions. The MCs contained fluorinated and partially fluorinated groups terminated by sulphonic or carboxylic acid groups. The fragmentation process in the MCs was studied by spin trapping electron spin resonance (ESR) methods, using 5,5‐dimethylpyrroline‐N‐oxide (DMPO), N‐tert‐butyl‐α‐phenylnitrone (PBN) and 2‐methyl‐2‐nitrosopropane (MNP) as the spin traps. The objective of these experiments was to assess the effect of the type of ionic groups (sulphonic or carboxylic) and of fluorine substitution on the spin adducts detected. DMPO experiments led to the detection of spin adducts of ^·OH and of carbon‐centred radicals (CCRs), and allowed the determination of the ^·OH attack site on the ionic and/or on the protiated or fluorinated groups. CCR adducts were also detected when using PBN as a spin trap; a key point in the interpretation of the PBN results was, however, the realisation that MNP is formed during PBN exposure to UV irradiation and oxygen or other oxidants such as H₂O₂. Experiments with MNP as the spin trap were the most informative in terms of structural details for adducts obtained from each MC. The results allowed the identification of CCRs present as adducts, based on large hyperfine splittings (hfs) from, and the number of, interacting ¹⁹F nuclei; in addition, oxygen‐centred radicals (OCRs) as MNP adducts were also identified, with much lower hfs from ¹⁹F nuclei. Taken together, the results deduced by spin trapping suggest that both sulphonic acid and acetic acid groups can be attacked by ^·OH radicals and confirm two possible degradation mechanisms in Nafion membranes: initiated at the backbone and at the side chain.     

An electron spin resonance and photoluminescence investigation of the effect of annealing temperature on Gd-doped La2Zr2O7 nano-ceramics

Lanthanum zirconate pyrochlore (La₂Zr₂O₇=LZO) is considered as a potential ceramic host matrix for nuclear waste immobilization. In this context, incorporation of Gd ions, a surrogate for trivalent minor actinides, in the LZO host was investigated. Undoped and Gd doped LZO samples were synthesized using a low temperature gel-combustion route and characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), dynamic light scattering (DLS), electron spin resonance (ESR) and photoluminescence (PL) spectroscopic techniques. It was observed that even at 500 °C, a single phase pyrochlore could be stabilized without any impurity phase. The average particle size of the synthesized product was estimated to be 85–90 nm. At lower temperatures, it was observed that, the Gd ions were present mostly on the surface of the LZO host which diffused into the lattice and replaced the La³⁺ ions after annealing at 700 °C for 5 h. Due to difference in the ionic radii, the environment around the Gd ion was highly asymmetric. This was further confirmed by PL investigations wherein upon excitation with UV radiation, the nano ceramics exhibited strong and sharp transition at 310 nm suggesting the existence of Gd³⁺ions in a D_2d geometry. Upon annealing, agglomeration of the particles was taking place reducing the surface defects and increasing the PL intensity as well as life time values.     

PET黏合剂及其弹性体热解与推进剂热解相关性研究

采用差示扫描量热/热重(DSC/TG)和裂解气相色谱质谱联用(Py-GC/MS)分析技术研究了PET黏合剂体系、PET/TDI弹性体以及含PET黏合剂体系的简单组分推进剂的热分解特性和热裂解产物状况,探索了PET弹性体的热分解与含PET黏合剂体系的推进剂热解性能之间的相关性.研究结果表明,混合硝酸酯增塑的PET黏合剂体...     

美国《工程索引》及收录《火炸药学报》论文的统计分析

介绍了美国《工程索引》(Ei)的历史及主要产品,讨论了Ei数据库的选刊原则以及Ei对文摘的具体要求,论述了Ei来源期刊的3个层次,包括核心期刊、选做期刊及扩充期刊,对2000-2002年Ei收录《火炸药学报》论文进行了统计分析。     

The Interrelation Between the Thermal Decomposition of Lead Salt and the Platonization Mechanism of Double-Base Propellants

The effects of carbon black, cupric adipate and RDX on the thermal decomposition behaviour of lead flake in double-base system are investigated by DSC measurement. The results show that the thermal decomposition peak of lead flake decomposition shifts to lower temperature with the addition of carbon black, cupric adipate and RDX, and the exotherm heat of lead flake increases with the addition of carbon black and RDX. DSC results are compared with the burning characteristics of practical plateau propellants, the chemical reactions involving lead salts near the burning surface are assumed. The mechanism of the effects of ballistic modifiers and RDX on the phenomenon of platonization are discussed.     

Investigation on Decomposition Kinetic and Thermal Stability of Metallocene Catalysts

Data on thermal stability of metallocene catalysts such as bis(n-butyl cyclopentadienyl) zirconium dichloride and bis(t-butyl cyclopentadienyl) zirconium dichloride is required because of their application in high temperature polymerization process. In the present study, the thermal stability of the bis(n-butyl cyclopentadienyl) zirconium dichloride and bis(t-butyl cyclopentadienyl) zirconium dichloride was determined by differential scanning calorimetry (DSC) and simultaneous thermogravimetry-differential thermal analysis (TG-DTA) techniques. The results of TG analysis revealed that the main thermal degradation for the bis(n-butyl cyclopentadienyl) zirconium dichloride and bis(t-butyl cyclopentadienyl) zirconium dichloride occurs in the temperature ranges of 194–360 °C and 195–350 °C, respectively. On the other hand, TG-DTA analysis indicated that bis(n-butyl cyclopentadienyl) zirconium dichloride melts (about 98.7 °C) before it decomposes. However, the thermal decomposition of the bis(t-butyl cyclopentadienyl) zirconium dichloride was started simultaneously with its melting. Also, the kinetic parameters such as activation energy and frequency factor for both compounds were obtained from the DSC data by non-isothermal methods proposed by Kissinger and Ozawa. Based on the values of activation energy obtained by Kissinger and Ozawa methods, the following order for the thermal stability was noticed: bis(t-butyl cyclopentadienyl) zirconium dichloride >bis(n-butyl cyclopentadienyl) zirconium dichloride. Finally, the values of ΔS^#, ΔH^# and ΔG^# of their decomposition reaction were calculated.     

超级铝热剂Al/Fe_2O_3对硝化棉热分解特性的影响

采用水热法制备了纳米Fe_2O_3,并用超声分散法将其与纳米Al颗粒复合制备了超级铝热剂Al/Fe_2O_3,利用X-射线粉末衍射(XRD)、透射电子显微镜(TEM)、扫描电镜及能量散射光谱仪(SEM-EDS)对复合物的物相、组成、形貌和结构进行了分析表征,采用差示扫描量热法(DSC)和热红联用技术(TG-FTIR)研究了Al/Fe_2O_3对硝化棉(NC)热分解过程的影响。结果表明,Al/Fe_2O_3-NC和NC的热分解过程遵循Avrami-Erofeev方程f(α)=1.5(1-α)[-ln(1-α)]1/3;超级铝热剂Al/Fe_2O_3可降低硝化棉的表观活化能、临界点火温度和临界爆炸温度,在促进硝化棉O-NO_2键断裂和凝聚相二次自催化反应中起到至关重要的作用。     

纳米ZnO立方体催化AP热分解及其在HTPE推进剂中的应用

为改善高氯酸铵(AP)的性能,从而改善复合固体推进剂的燃烧性能,采用AP辅助的金属有机骨架结构(MOF)热分解法合成纳米ZnO立方体催化剂(n-ZnO/cube);采用XRD、FESEM、TEM等对其形貌进行了表征,分析了其比表面积和孔径分布;采用TG-DTA分析了其对AP热分解的影响;将其加入到HTPE推进剂中,测试了其对推进剂工艺性能、安全性能、力学性能及燃烧性能的影响。结果表明,n-ZnO/cube催化剂具有大的比表面积(70.5m2/g)和大量的孔道结构,将AP热分解的高温分解峰从413℃降至279℃,放热量从584J/g增至1520J/g,分解活化能从151.1kJ/mol降至65.3kJ/mol;将质量分数2%的n-ZnO/cube加入到HTPE推进剂中,推进剂的燃速(20℃,6.86MPa)从12.01mm/s提高到16.16mm/s,工艺性能、安全性能、力学性能、燃速压强指数(0.42,20℃,3~16MPa)、燃速温度敏感系数(2.02×10^-3℃^-1,-55~70℃,6.86MPa)均未受到明显影响,表明纳米ZnO立方体结构对AP热分解表现出良好的催化性能,是HTPE推进剂的一种具有潜力的燃烧调节剂。     

Electron Spin Resonance Evaluation of Buccal Membrane Fluidity Alterations by Sodium Caprylate and L-Menthol

The ability of sodium caprylate and l-menthol to fluidize phospholipid bilayers composed of lipids simulating the buccal epithelium was investigated using electron spin resonance (ESR) to evaluate the action of these agents as permeation enhancers. 5-Doxyl stearic acid (5-DSA) and 16-doxyl stearic acid (16-DSA) were used as spin labels to identify alterations in membrane fluidity near the polar head groups or inner acyl regions of the lipid bilayer, respectively. The molecular motion of both 5-DSA and 16-DSA showed increased disorder near the polar and inner hydrophobic regions of the bilayer in the presence of sodium caprylate suggesting fluidization in both the regions, which contributes to its permeation enhancing effects. L-menthol decreased the order parameter for 16-DSA, showing membrane fluidization only in the inner acyl regions of the bilayer, which also corresponded to its weaker permeation enhancing effects. The rapid evaluation of changes in fluidity of the bilayer in the presence of potential permeation enhancers using ESR enables improved selection of effective permeation enhancers and enhancer combinations based on their effect on membrane fluidization.     

Influence of Electron Beam Irradiation and Coupling Agents on the Thermal Stability of Sugar Cane Bagasse Fiber-Thermoplastics Scrape Composite

The influence of blending of sugar cane bagasse with thermoplastics scrape as well as incorporation of some coupling agents has been conducted using thermogravimetric analysis (TGA). In addition, the effect of electron beam preirradiation of low density polyethylene on the properties of the bagasse-LDPE composite was also studied. Simulation of TGA data reveals that the presence of bagasse fiber accelerates the volatilization of either polypropylene or polyvinylchloride. On the other hand, polyethylene and polystyrene were stable against the heat evolved during the pyrolysis of bagasse fibers. Also, it was found that incorporation of a mixture of pentaerithrol tetraacrylate (PETA) and dicumyl peroxide (DCP) as coupling agents improve the thermal stability of low density polyethylene whereas the role of irradiation was insignificant. Moreover, pronounced enhancement in the thermal stability was detected in polypropylene followed by polystyrene and polyvinylchloride on using PETA.     

Preliminary Characterization of Propellants Based on p(GA/BAMO) and pAMMO Binders

In previous papers, the synthesis and characterization of OH‐terminated glycidyl azide‐r‐(3,3‐bis(azidomethyl)oxetane) copolymers (GA/BAMO) and poly‐3‐azidomethyl‐3‐methyl oxetane (pAMMO) by azidation of their respective polymeric substrates were described. The main objective was the preparation of amorphous azido‐polymers, as substitutes of hydroxy‐terminated polybutadiene (HTPB) in new formulations of energetic propellants. Here, the subsequent characterization of both the binders is presented. First of all, several isocyanates were checked in order to optimize the curing reaction, and then two small‐scale formulations of a propellant, based on aluminium and ammonium perchlorate, were prepared and characterized. Finally, the mechanical properties and burning rate were compared to those of a similar propellant based on HTPB as binder.     

四硝基并哌嗪的催化热分解及机理研究

采用高压差示扫描量热法(PDSC)、热重分析法(TGA)和快速扫描傅里叶变换红外光谱法(FT-IR),研究了四硝基并哌嗪(TNAD)的热分解机理,并采用FT-IR技术和TG/MS(质谱)联用分析了TNAD热分解过程的凝聚相变化,确认其热分解机理与化学反应过程。研究表明,在1MPa压力下TNAD的分解过程较简单,无熔融吸热峰出现,属固相分解,主要放热峰出现在212.5～251.7℃。NTO-Pb、TNAD/φ-Pb、β-Cu和AD-Cu等铅铜盐对TNAD的催化作用明显,都能使其热分解反应提前,相比之下,β-Cu和NTO-Pb催化效果更好。炭黑、Al_2O_3、Al等添加剂对TNAD起到稀释作用,缓和了分解放热过程,可起到稳定燃烧的作用。TNAD热分解主要有2个历程,分解过程中产生的主要气体产物为HCHO、NO、HCN和-C2_H_2、-CHO等碎片离子。     

Effect of Fe2O3 in Fe2O3/AP Composite Particles on Thermal Decomposition of AP and on Burning Rate of the Composite Propellant

A technique of composite processing of Fe₂O₃ and ammonium perchlorate (AP) was employed in making the propellant. The effects of composite processing of Fe₂O₃ on catalytic activity, on the thermal decomposition of AP, and on the burning rate of the composite propellant were investigated in this paper. Fe₂O₃/AP composite particles were prepared by a novel solvent‐nonsolvent method. The results show that AP is successfully coated on the surface of Fe₂O₃. Composite processing of Fe₂O₃ and AP can improve the catalytic activity of Fe₂O₃. Fe₂O₃ exhibits better catalytic effect with increasing Fe₂O₃ content. The larger interface between Fe₂O₃ and AP and lower density of composite propellant (with the added Fe₂O₃/AP composite particles) are responsible for the enhancement of the catalytic activity of Fe₂O₃.     

超微细 Cu_2O 对 RDX/AP/HTPB 推进剂组分热分解特性影响的研究

通过氧化还原法在微乳液中合成了超微细的Ｃｕ２Ｏ（０．２μｍ）,并用ＤＴＡ研究了超细Ｃｕ２Ｏ、市购化学纯Ｃｕ２Ｏ（３μｍ）、ＹＢ、ＱＣ及它们的不同组合对ＲＤＸ／ＡＰ／ＨＴＰＢ推进剂组分热分解特性的影响。实验结果表明：超细Ｃｕ２Ｏ能大幅度降低ＡＰ和ＲＤＸ／ＡＰ（质量比１∶２）混合体系的分解活化能,其催化作用与市购Ｃｕ２Ｏ相比有较大的增强。与ＹＢ组合对ＡＰ和ＲＤＸ／ＡＰ混合体系的催化有明显的协同效应,对ＲＤＸ也有一定的催化作用。     

Electron Spin Resonance of High-Spin Co2+ in Alkali Borate and Alkali Germanate Glasses

Electron spin resonance spectra of high-spin Co²⁺ doped in alkali borate and alkali germanate glasses have been measured at 4.2 K. For comparison, the corresponding spectrum in a 33K₂O·67SiO₂ glass has also been measured. On the basis of the spectral line shape, the observed spectra, together with those in the literature, seem to be classified into four spectral types that represent Co²⁺ ions in octahedral coordination, a mixture of some types of coordination, tetrahedral coordination with nearly axial symmetry, and distorted tetrahedral coordination.     

Evaluation of Lattice Site and Valence of Mn and Fe in Polycrystalline PbTiO3 by Electron Spin Resonance and Thermogravimetry

The oxides of Mn and Fe or combinations of La₂O₃ with these oxides were incorporated into PbTiO₃ under defined thermodynamic conditions. The substitution reaction of these additives was examined gravimetrically. At low partial pressures of O₂ and PbO vapor, Mn²⁺ and Fe²⁺ are formed at the A sites, and Mn³⁺ and Fe³⁺ enter both A and B sites. At higher partial pressures of PbO, Mn⁴⁺ is most probably formed at the B sites.
The Mn²⁺, Mn⁴⁺, and Fe³⁺ were determined by ESR.