Kinetic Parameters of PBX Based on Cis‐1,3,4,6‐tetranitroocta‐hydroimidazo‐[4,5‐d] imidazole Obtained by Isoconversional Methods using Different Thermal Analysis Techniques

The thermal decomposition kinetics of the interesting polycyclic nitramine cis‐1,3,4,6‐tetranitrooctahydroimidazo‐[4,5‐d]imidazole (BCHMX) and its polymer bonded explosive (PBX) based on polyurethane matrix, have been investigated using different thermal analysis techniques and methods. The used polyurethane matrix is based on hydroxyl‐terminated polybutadiene (HTPB) cured by hexamethylene diisocyanate (HMDI). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used nonisothermally, whereas the vacuum stability test (VST) was used isothermally. Kinetic parameters were determined by using isoconversional (model‐free) methods. Furthermore, the Advanced Kinetics and Technology Solution (AKTS) software was used to determine the kinetic parameters of the studied samples in order to provide a comparison. It was found that the decomposition temperature of BCHMX/HTPB is lower than that of pure BCHMX. All the applied techniques as well as computational results showed that BCHMX/HTPB has a lower activation energy than pure BCHMX. The different methods used, Kissinger, Ozawa, Flynn, and Wall (OFW) and Kissinger‐Akahira‐Sunose (KAS) methods presented activation energies in the same range of the AKTS software results. Also the results proved that VST technique could be a useful tool to present results suitable for calculation of the kinetic parameters of explosives.     

纳米铝粉对硝胺炸药热分解催化性能的影响

采用直流电弧等离子体蒸发法制备了高纯度的纳米铝粉,并用比表面积分析仪和扫描电子显微镜(SEM)对样品进行了表征.将纳米铝粉与硝胺炸药HMX和RDX用研磨混合法制成混合粒子,用DSC对单质HMX和RDX炸药以及纳米铝粉/硝胺炸药混合物进行催化特性测试,并对样品的热分解动力学和热力学参数进行了计算和对比.结果表明,加入纳米铝粉后,HMX和RDX在不同升温速率(2、5、10、20 K/min)下的放热峰峰温降低,活化能分别降低15和16 kJ/mol,热力学参数都有明显变化.纳米铝粉对HMX和RDX有明显的热分解催化作用.     

Co-pyrolytic behaviors of biomass and polystyrene: Kinetics,thermodynamics and evolved gas analysis

The pyrolytic degradation mechanism of chestnut shell (CNS) and its blend with waste polystyrene (PS) were investigated. Individual pyrolysis behavior of samples obtained separately was compared with those of the blends using a combined TGA/MS/FT-IR system. To elaborate kinetic analysis and to determine kinetic parameters, distributed activation energy model (DAEM) was used. The average activation energy of co-pyrolytic decomposition reaction was 191.6 kJ/mol, while the activation energy of the pyrolysis of CNS and PS was 175.2 and 208.9 kJ/mol, respectively. Friedman and Flynn-Wall-Ozawa iso-conversional methods were applied and the results were found to be consistent with the models. To express the presence of complex reaction mechanisms and the interactions of the radicals, thermodynamic parameters were also calculated. Finally, the pathways for main volatiles were established, and their relationship with the pyrolytic degradation was suggested.     

原位聚合包覆HMX的研究

为探索制备PBX的新方法,利用原位聚合反应,直接在HMX表面包覆一层热塑性高聚物,获得了分别以端羟基聚丁二烯(HTPB),聚叠氮缩水甘油醚(GAP)、3,3-双(叠氮甲基)环氧丁烷-四氢呋喃共聚醚(BAMO-THF)3种黏结剂包覆的PBX.通过光学显微镜、显微-红外、光电子能谱(XPS)、元素分析和机械感度测定对包覆效果进行表征.结果表明,HMX表面较均匀地包覆上了一层聚合物,黏结剂的质量分数约为4%～5%,包覆HTPB的HMX机械感度明显下降,而包覆GAP和BAMO-THF的HMX机械感度略有降低.     

Study of the Elaboration of HMX and HMX Composites by the Spray Flash Evaporation Process

The Spray Flash Evaporation (SFE) process invented and developed at the NS3E laboratory allows obtaining different nanosized explosives (TNT, RDX, CL‐20…). This process is based on the very fast evaporation of the solvent due to the drastic modification of pressure and temperature leading to the crystallization of the molecules present in solution into nanometric or submicrometric particles. Here, we show the possibility to prepare pure HMX (Octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine) or HMX based composites at the nanoscale using this process. This study mainly focuses on the size, morphology and crystallographic phases obtained for HMX and HMX/TNT composites depending on the experimental conditions (temperature, pressure, solution concentration…) used during the elaboration. For this purpose, the results obtained from scanning electron microscopy, X‐ray diffraction and Raman spectroscopy are discussed.     

Thermal and spectroscopic measurements of some energetic compositions and corresponding aerosols obtained

Studies on specific thermochemical processes contribute to the understanding of combustion processes and, meanwhile, to the calculus of the safety characteristics and the systems design parameters. In this paper, five different compositions have been studied through TGA and DTA. The reaction rate constants and the activation energies have been determined. Also, the solid combustion products obtained have been evaluated through SEM, EDX, and XPS. Nonisothermal kinetic analyses performed yield results that prove an important difference among the first fire compositions, where the activation energies are considerable, up to 400 kJ/mol, in comparison with the activation energies of the flare compositions, which are lower, 150–250 kJ/mol.     

Synthesis,Characterization and Properties of Nitropolybutadiene as Energetic Plasticizer for NHTPB Binder

The nitration of low molecular weight polybutadiene (PB) by a convenient and inexpensive procedure was investigated. To retain the unique physico‐chemical properties of the plasticizer, it was nitrated to an extent of 10 % double bonds. The product nitropolybutadiene (NPB) was characterized by FT‐IR and ¹H NMR spectroscopy as well as GPC, DSC, and TGA methods. The kinetic parameters for the decomposition of NPB from room temperature to 400 °C were obtained from non‐isothermal DSC. The changes in glass transition temperature (T _g) and inert uncured binder systems were used for determination of its efficiency as plasticizer. NPB was used in cured and unfilled nitro‐hydroxyl terminated polybutadiene (NHTPB) binder. Isothermal thermogravimetric analysis (Iso‐TGA) was employed to determine the migration rate in cured and unfilled HTPB binder systems compared to the dioctyladiphate (DOA) plasticizer. It was found that the exudation of the NPB plasticizer is slower than that of the DOA plasticizer. Thus, the NHTPB/NPB binder system (binder/plasticizer) presents more convenient mechanical properties than HTPB/DOA and is a promising new energetic binder system for polymer bonded explosives.     

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"。     

典型垃圾材料的热分解动力学

对垃圾材料的热分解动力学研究目的在于研究垃圾材料的热解特性,文中对典型垃圾材料聚氯乙烯(PVC)和纸进行热分解动力学研究.用综合热分析仪分别测试PVC及纸在升温速率为10,15,20,30 K/min时的TG-DSC曲线,获取PVC和纸在最大质量损失速率时的温度Tmax及其他动力学参数.然后用Kissinger法和Fl...     

CO2 gasification kinetics of two alberta coal chars

CO₂ gasification kinetics of chars from two Alberta coals (Obed Mountain, high volatile bituminous and Highvale, subbituminous) have been studied using a thermogravimetric analyzer (TGA) and a fixed bed reactor. Charification and gasification reactions were performed sequentially in both the TGA instrument and in the fixed bed reactor to simulate real gasifier operating conditions. TGA and fixed bed data were processed numerically to evaluate the kinetic rate of CO₂ gasification of the chars. Calculated gasification kinetics could be correlated using both the volume reaction and the grain models. Activation energies of the kinetic rate constants were near 200 kJ/mol for both Highvale and Obed Mountain coal chars using the TGA data. The activation energies calculated for the Obed Mountain coal char using the fixed bed reactor were about 250 kJ/mol. For all the cases studied the calculated activation energies were nearly the same for both the volume and grain reaction models.     

Pb-TKX-50燃烧催化剂的合成及热分解性能

以二氯乙二肟、二甲基甲酰胺、叠氮化钠、盐酸羟胺和硝酸铅等为原料,合成了1,1-二羟基-5,5′-联四唑羟胺铅盐(Pb-TKX-50)燃烧催化剂,研究了Pb-TKX-50对推进剂机械感度的影响以及与推进剂组分的相容性;利用差示扫描量热法和热重法研究了Pb-TKX-50在不同升温速率下的热分解过程,计算其表观活化能(E K和E O)和指前因子(A K),得到其热分解动力学参数、热分解机理函数、热爆炸温度和热力学性质。结果表明,在推进剂配方中加入Pb-TKX-50燃烧催化剂,可以改善其撞击感度和摩擦感度,且与推进剂组分的相容性良好;Pb-TKX-50的主峰分解温度相对于TKX-50的主峰分解温度显著提高,说明其热稳定性显著提高。Ozawa法和Kissinger法得到Pb-TKX-50的表观活化能分别为181.45 kJ/mol和182.49 kJ/mol,且热分解过程符合Avrami-Erofeev方程;Pb-TKX-50的自加速分解温度和爆炸临界温度分别为500.53 K和544.33 K,表明其热稳定性良好;Pb-TKX-50催化剂的热分解自由能(ΔG^≠)为158.87 kJ/mol,活化焓(ΔH^≠)为187.03 kJ/mol,活化熵(ΔS≠)为52.98 kJ/mol。     

Study of Plastic Explosives based on Attractive Cyclic Nitramines Part I. Detonation Characteristics of Explosives with PIB Binder

Four plastic explosives based on energetic nitramines and a non‐energetic binder were prepared and studied. The nitramines were RDX (1,3,5‐trinitro‐1,3,5‐triazine), HMX (1,3,5,7‐tetranitro‐1,3,5,7‐tetrazine), BCHMX (cis‐1,3,4,6‐tetranitro‐octahydroimidazo‐[4,5‐d]imidazole) and HNIW (ε‐2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane, ε‐CL‐20). The binder was in all cases polyisobutylene (PIB) as in the standard composition C‐4. These powerful plastic explosives were compared to standard PETN‐based commercially available explosives Semtex 1A and Sprängdeg m/46. The detonation velocities were experimentally measured and compared to the ones calculated by the Kamlet–Jacobs method, CHEETAH and EXPLO5 Codes. The experimental detonation velocities as well as the calculated detonation parameters decrease in the following order: HNIW‐PIB>HMX‐PIB≥BCHMX‐PIB>RDX‐PIB>Sprändeg m/46≥Semtex 1A. Urizar coefficients for the various binders were calculated from experimental data.     

表面活性剂对HMX基PBX性能的影响

采用溶液-水悬浮法,以F2602为黏结剂,Span-80、Tween-80、PVA、糊精为表面活性剂,制备了HMX基PBX;采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、差式扫描量热仪(DSC)对其进行了表征和热分析,并测试了其撞击感度。结果表明,加入表面活性剂包覆后未改变HMX的晶体结构;以Span-80为表面活性剂时包覆得到的HMX基PBX表面最光滑,包覆密实且无明显外漏现象;加入表面活性剂Span-80、Tween-80、PVA、糊精后得到的HMX基PBX的表观活化能分别为438.05、217.74、406.64、356.14kJ/mol,与未加表面活性剂的样品相比降低了35.52、255.83、66.93、117.43kJ/mol;加入Span-80的HMX基PBX热爆炸临界温度约上升1℃,表明对PBX的安定性无明显影响,撞击感度特性落高(H50)由44.9cm增加到63.2cm,提高了40.76%。     

Preparation and Characterization of Reticular Nano‐HMX

Reticularly structured HMX (octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine) of nano‐size particles was simply prepared by reprecipitation at room temperature. The sample prepared by reprecipitation was characterized by SEM, TEM, XRD, DSC, and drop weight impact. The results of SEM and TEM indicated that spherical HMX particles of about 50 nm in diameter aggregated into reticularly structured conglomerates. There are two phases (γ‐ and β‐HMX) existing in the reticularly structured HMX as shown in the XRD pattern. It was also proved by DSC that the maximum energy release during decomposition of the reticularly structured HMX is at lower temperature. In addition, the testing result of drop weight impact showed that the reticularly structured HMX is less sensitive to impact.     

Preparation and Performance of Nano HMX/TNT Cocrystals

Cocrystals of 1,3,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane (HMX) and 2,4,6‐trinitrotoluene (TNT) with high energy and low sensitivity were obtained by a spray drying method. Scanning electron microscopy (SEM), X‐ray diffraction (XRD), and Fourier Transform Raman spectroscopy (FT‐Raman) were used to characterize the raw materials and cocrystals. Impact sensitivity and thermal decomposition properties of the cocrystals were tested and analyzed. The results show that microparticles prepared by the spray drying method are spherical in shape and 1–10 μm in size. The particles are aggregates of many tiny cocrystals, ranging from 50 nm to 200 nm. The formation of cocrystals originates from the N O ⋅⋅⋅ H hydrogen bonding between  NO₂ (HMX) and  CH₃ (TNT). Compared with raw HMX, the impact sensitivity of the cocrystals reduces obviously and it is much harder to decompose the cocrystal thermally.     

2,6-二氨基-3,5-二硝基吡啶-1-氧化物基PBX的热安全性研究

为了研究2,6-二氨基-3,5-二硝基吡啶-1-氧化物(ANPyO)基高聚物黏结炸药(PBX)的热安全性,分别以氟橡胶F2311和丁晴橡胶NBR-26为主体设计两种黏结剂体系,采用水悬浮-溶解-蒸馏法制备ANPyO基PBX炸药。利用扫描电子显微镜(SEM)、差示扫描量热法(DSC)和热重法(TG)表征不同黏结剂体系PBX的结构和性能,计算了两种黏结剂体系PBX的热分解动力学参数和热爆炸参数,并获得了被400K气氛环绕的半径为1m的球形、无限圆柱形或无限平板状PBX的热感度概率密度函数S(T)与温度T的关系曲线。结果表明,以丁晴橡胶NBR-26为黏结剂体系主体PBX的活化能E为173.19kJ/mol、指前因子ln(A/s-1)为28.58、自加速分解温度TSADT为550.01K、热点火温度Tbe为565.81K、热爆炸临界温度Tbp为625.06K;以氟橡胶F2311为黏结剂体系主体PBX的活化能E为143.78kJ/mol、指前因子ln(A/s-1)为22.89,自加速分解温度TSADT为539.99K,热点火温度Tbe为560.28K,热爆炸临界温度Tbp为615.55K;球形PBX的热安全性稍高于无限圆柱或平板状PBX,以丁晴橡胶NBR-26为黏结剂体系主体PBX的热安全性高于氟橡胶F2311为黏结剂体系主体PBX。     

Preparation and thermal decomposition of PS/AG microspheres

PS/Ag microspheres were prepared by electroless silver plating on PS microspheres. SEM, EDS, and XRD approved the successful formation of silver coatings on PS microspheres. The thermogravimetric analysis was studied using a TGA system. The Ozawa and Coats-Redfern methods were exploited to calculate activation energy and determine thermal decomposition mechanism. The thermal decomposition mechanism of pure PS microspheres was also investigated to draw comparisons with the mechanism of PS/Ag microspheres. It has been found that the thermal decomposition mechanism of PS/Ag microspheres and PS microspheres were both A₂ model. The activation energy of PS microspheres and PS/Ag microspheres is 76.76 kJ/mol and 78.61 kJ/mol, respectively. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

胆固醇与β-环糊精包合物热稳定性及热动力学研究

采用非等温热重法研究了 β 环糊精和胆固醇包合物的热分解反应动力学。实验结果表明 ,β 环糊精和胆固醇包合物热分解反应级数大于 1,用Ozawa(1)法和Reich法求得热分解反应的平均表观活化能分别为 78 6 9kJ/mol、86 82kJ/mol。较低的表观活化能说明包合物的热稳定性与 β 环糊精和胆固醇之间的匹配性有关     

A Groundbreaking Stepwise Protocol to Prepare HMX from DPT: New Mechanism Hypothesis and Corresponding Process Study

1,3,5,7‐Tetranitro‐1,3,5,7‐tetraazacyclooctane(HMX) is one of the most powerful and widely used explosives. 3,7‐Dinitro‐1,3,5,7‐tetraazabicyclo[3.3.1] (DPT) is an important precursor in the production of HMX. A new reaction mechanism including nitrolysis, nitrosolysis and nitrolysis processes in fuming HNO₃ was put forward. The stable key intermediate 1‐nitroso‐3,5,7‐trinitro‐1,3,5,7‐tetraazacyclooctane (MNX) was isolated and characterized. Based on the new mechanism, a stepwise method to prepare HMX from DPT was developed. The influence factors on the yields of MNX such as reaction temperature, loading amounts of HNO₃, NaNO₂ and NH₄NO₃ were investigated. Under the optimized conditions, MNX was obtained with a satisfactory yield of 84.0 %. MNX could be efficiently and smoothly nitrolyzed in fuming nitric acid and afforded pure β‐HMX with excellent yield up to 92.8 %. The overall yield of the stepwise procedure was as high as 78.0 %, much higher than traditional one‐pot nitrolysis protocols.     

Laser‐Induced Deflagration of Unconfined HMX – The Effect of Energetic Binders

The effect of three energetic binders [poly(3‐methyl‐3‐nitratomethyloxetane (polyNIMMO), polyglycidyl nitrate (polyGLYN) and an energetic polyphosphazene (PPZ‐E) – all at 10%] on the unconfined laser‐induced deflagration of cyclotetramethylene tetranitramine, commonly known as High Melting point Explosive (HMX) by a near IR (NIR) diode laser (801 nm) has been examined. Hydroxyl terminated polybutadiene (HTPB) and PPZ (the precursor to PPZ‐E – before nitration) were used as reference materials. The formulations required the addition of an optical sensitizer – carbon black (CB) – for ignition. At the designated threshold flux density of 2.3 kW cm⁻², a minimum of ∼1 wt.‐% CB was needed for the reliable ignition of unbound HMX and its formulations with polyGLYN, PPZ‐E and PPZ. Under similar conditions HMX/polyNIMMO and HMX/HTPB required 3% CB. Ignition maps (ignition time versus laser flux density) have been constructed for the five formulations. Comparison of ignition times and ignition energy densities for HMX and HMX/polyGLYN showed this binder to have only a marginal effect. In contrast, HTPB, PPZ and PPZ‐E all retarded HMX ignition at the threshold flux density, but showed negligible effect at higher flux densities. As PPZ and PPZ‐E produced both similar delays in the ignition time and similar increases in the flame development times (10–90%) at the threshold flux density, the inhibition of the HMX ignition by these PPZs appears to be largely independent of the polymer energy content. Such characteristics could be useful for high performance and insensitive energetic formulations. PolyNIMMO (3% CB) increased the ignition time of HMX only slightly at 2.3 kW cm⁻². However, at this threshold flux level the HMX flame development times with polyNIMMO or HTPB were much longer than that for the unbound material; this effect is attributed to the enhanced CB content.