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Journal Cover Propellants, Explosives, Pyrotechnics
  [SJR: 0.847]   [H-I: 45]   [305 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0721-3115 - ISSN (Online) 1521-4087
   Published by John Wiley and Sons Homepage  [1589 journals]
  • Measurement, Correlation and Thermodynamics of Solubility of
           2,6-Diamino-3,5-Dinitropyrazine-1-Oxide (LLM-105) in Eight Solvents
    • Authors: Rupeng Bu; Xiaoqing Zhou, Qi Huang, Yanwu Yu, Hongzhen Li
      Abstract: The solubility of insensitive explosive 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) in dimethyl sulphoxide (DMSO), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), N,N-diethylformamide (DEF), 1,4-dioxane, 1,4-butyrolactone, ethyl acetate and 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim]CF3SO3), were measured by a polythermal method in the temperature range of 293.15 K to 375.15 K at the atmospheric pressure. The solubility of LLM-105 decreased in the order of DMSO, NMP, DMF, DEF, 1,4-butyrolactone, [Bmim]CF3SO3, 1,4-dioxane, ethyl acetate. With higher temperature, the solubility of LLM-105 increased in all solvents. The solubility data was correlated against temperature with the modified Apelblat equation and Ideal solution model. In addition, the dissolution enthalpy, entropy, and mole Gibbs free energy of LLM-105 in each solvent were also calculated from the experimental solubility data by using van′t Hoff equation with the temperature dependence. The results show that the dissolution process of LLM-105 in these solvents is endothermic and the mechanism is the entropy-driving. DMSO is suggested as the appropriate solvent for the cooling crystallization or drowning-out crystallization of LLM-105.
      PubDate: 2017-12-04T09:25:26.913204-05:
      DOI: 10.1002/prep.201700123
       
  • Evaluation of the Deuterium Isotope Effect in the Detonation of Aluminum
           Containing Explosives
    • Authors: Bryce C. Tappan; Patrick R. Bowden, Virginia W. Manner, Jeffery A. Leiding, Micah S. Jakulewicz
      Abstract: During or shortly after a detonation in condensed explosives, the reaction rates and the physical mechanism controlling aluminum reaction is poorly understood. We utilize the kinetic isotope effect to probe Al reactions in detonation product gases in aluminized, protonated and deuterated high explosives using high-fidelity detonation velocity and cylinder wall expansion velocity measurements. By observation of the profile of cylinder wall velocity versus time, we are able to determine the timing of aluminum contribution to energy release in product gases and observe the presence or absence of rate changes isotopic substitution. By comparison of the Al oxidation with lithium fluoride (LiF), data indicate that Al oxidation occurs on an extremely fast time scale, with post-detonation kinetic isotope effects observed in carbon containing formulations.
      PubDate: 2017-12-04T08:10:36.245614-05:
      DOI: 10.1002/prep.201700197
       
  • Practical Remediation of 3-Nitro-1,2,4-triazol-5-one Wastewater
    • Authors: Siao Chien Chew; Mat Tennant, Nathalie Mai, Daniel McAteer, Jean-François Pons
      Abstract: Limiting environmental impact is a top priority for the chemical industry, and manufacturing practices need to be well controlled to avoid any potential contamination. In order to reduce waste streams during the processing of 3-nitro-1,2,4-triazol-5-one (NTO), potentially evironmental hazardous at concentrations of 1 g/l, we investigated the potential remediation and recycling of water using a wide range of commercial sorption media. We studied the effect of experimental conditions, including flow rate, initial contaminant concentration and temperature. This led to the selection of Amberlyst A26 OH in a batch process and Activated Carbon in continuous flow, as the most effective sorption methods. Using high performance liquid chromatography photodiode array detection (HPLC-PDA), NTO was quantified from solutions, before and after remediation, showing a complete removal from a 10 g/l NTO solution. Our purification method therefore appears to be suitable for the remediation of NTO-contaminated wastewater.
      PubDate: 2017-11-30T07:20:23.640775-05:
      DOI: 10.1002/prep.201700256
       
  • Application and Properties of Nano-sized RDX in CMDB Propellant with Low
           Solid Content
    • Authors: Jie Liu; Xiang Ke, Lei Xiao, Gazi Hao, Yuanbo Rong, Chengsu Jin, Wei Jiang, Fengsheng Li
      Abstract: Composite modified double-base (CMDB) propellant, benefitting from the outstanding performances of high energy and low signature, has attracted increasing focus in the past decade. To improve the integrative performance, such as enhancing the mechanical property and decreasing the sensitivity, CMDB propellant with low solid content containing nano-sized RDX has been prepared. The microstructure, mechanical properties, sensitivity and combustion performance of the prepared propellant are studied. Results have shown that the interface of the CMDB propellant contained nano-sized RDX (N-CMDB) is more compact and the internal defects are less than those of the CMDB propellant with micro-sized RDX (M-CMDB). Compared with the maximum tensile strength (σm) and the corresponding elongation at maximum tensile strength (ϵm) of M-CMDB, the σm values of N-CMDB are improved by 37.4 % at +50 °C, 27.5 % at +20 °C and 26.7 % at −40 °C, and the ϵm values are increased by 16.1 %, 19.4 % and 39.6 %, separately. Moreover, the friction and impact sensitivities of N-CMDB propellant are decreased by 51.3 % and 50.4 %, respectively. In the range of 8–18 MPa, the combustion performance of N-MCDB propellant has been demonstrated more attractive with higher burning rate coefficient (8.69210.950) and lower pressure exponent (0.3840.299). All these results lead us to believe that the usage of nano-sized explosives will contribute to improve the comprehensive performance of CMDB propellants and promote their application in weapon system.
      PubDate: 2017-11-30T05:55:28.833463-05:
      DOI: 10.1002/prep.201700211
       
  • Energetic Nanocomposites as Burn Rate Catalyst for Composite Solid
           Propellants
    • Authors: Vrushali Bagalkote; Dan Grinstein, Benveniste Natan
      Abstract: In the present study the effect of addition of Al/Fe2O3 based energetic nanocomposites (ENC) to non-aluminized and aluminized propellants was investigated. Comparative study was carried out using n-Fe2O3 as burn rate catalyst. Ferric oxide xerogel and Al/Fe2O3 ENC were synthesized by sol-gel method. The dried xerogel was characterised by Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). TEM and SEM images reveal presence of porous interconnected ferric oxide clusters of size 3–5 nm and intimate mixing of the ingredients at nanoscale in case of ENC. XRD analysis shows amorphous nature of the ferric oxide xerogel. Fe2O3 and FeO(OH) are the major constituents (>84 %) of the xerogel as confirmed by XPS analysis. Thermal analysis of the ENC indicates that the composition is energetic in nature. Sensitivity analysis was carried out to assess the safety of the ENC during propellant processing. The differential scanning calorimetry (DSC) results for propellant samples show that the Al/Fe2O3 ENC is a better catalyst for AP decomposition than n−Fe2O3. Burn rate studies of ENC catalyzed propellants with μ-Al and with n-Al were carried out using acoustic strand burner. The results indicate that ENCs can be promising catalysts for composite propellants.
      PubDate: 2017-11-28T07:07:15.014037-05:
      DOI: 10.1002/prep.201700095
       
  • Copolymers based on GAP and 1,2-Epoxyhexane as Promising Prepolymers for
           Energetic Binder Systems
    • Authors: Sven Hafner; Thomas Keicher, Thomas M. Klapötke
      Abstract: Copolymers of epichlorohydrin (ECH) and 1,2-epoxyhexane (EpH) have been synthesized via cationic ring-opening polymerization using BF3×THF as a catalyst. Structures of the resulting polymers have been confirmed by IR and NMR spectroscopy and GPC. In a subsequent reaction with NaN3 in DMSO, the halogenated precursors were completely azidated, which was confirmed by the same spectroscopic methods. The introduced pendant n-butyl chains act as an internal plasticizer by lowering the glass transition temperature (Tg) of the copolymers compared to the reference compound glycidyl azide polymer (GAP). Compared to GAP in a similar molecular weight range, the copolymers also showed reduced viscosity. These properties make the described copolymers interesting candidates for use as energetic binders in cast-cure applications.
      PubDate: 2017-11-28T07:06:04.537367-05:
      DOI: 10.1002/prep.201700198
       
  • Thermal Stability of Explosive Mixture with Additives at Different Ambient
           Temperatures
    • Authors: Bouras Nassim; Qi Zhang
      Abstract: Thermal stability of explosive mixture containing solid-liquid phase of trinitrohexahydrotriazine (RDX), isopropyl nitrate (IPN, 2-propyl nitrate) and aluminum powder (Al) with addition of different rates of 5 %, 10 %, 15 % and 20 % of sulfuric acid H2SO4 to the (RDX/IPN/Al) mixture was measured based on numerical simulation. Kissinger, equation of state (EOS) method and Maxwell approximation were used to compute the physic-chemical characteristics of the mixture. We add an amount of acid to present a new explosive component. To obtain the ignition temperature, Cookoff model of cylindrical test is performed. The heating process of mixture at different ambient temperatures was progressed, and the ignition temperature was found that it depends on both acid rate added and different ambient temperatures applied and focused by SADT analysis. Temperature distributions over time, different ambient temperatures effect on ignition delay time, ignition position are carried out.
      PubDate: 2017-11-28T04:21:38.484452-05:
      DOI: 10.1002/prep.201700204
       
  • Observation of Reverse Jetting from a Semi-hollow EFP after Perforating a
           Finite Thickness Composite Armour Panel
    • Authors: Frederik J. Mostert; Izak M. Snyman, Gary Corderley
      Abstract: A jet of material was observed exiting from the rear of the remnants of an initially semi-hollow explosively formed projectile, which perforated a finite thickness composite armour panel. The observation of this phenomenon was made by means of flash-X-ray photography at two different sub-millisecond times for a copper EFP that impacted the panel at above 2000 m/s. The jet exhibited remarkably similar characteristics to what is typically observed for shaped charge jets for similar liner materials. Progressive necking was observed in the jet and the velocity differences between necked sections were characterized. Simulation of a similar generic event by the ANSYS Autodyn hydrocode showed that reverse jet formation is possible for specific EFP geometries and impact conditions. The relatively low velocities of the jet elements in terms of the laboratory coordinates, holds promise for the soft recovery of the jetted particles.
      PubDate: 2017-11-20T06:10:24.399985-05:
      DOI: 10.1002/prep.201700239
       
  • The Effect of Some Amines on Ignition Delay Time of Dimethyl Amino Ethyl
           Azide (DMAZ) and White Fuming Nitric Acid (WFNA)
    • Authors: Shahram G. Pakdehi; Bahman Shirzadi
      Abstract: Dimethyl amino ethyl azide (DMAZ), as a non-carcinogen liquid fuel, is a good fuel in space programs. However, it suffers from high ignition delay (ID) time with liquid oxidizer white fuming nitric acid (WFNA). DMAZ were blended with amines in order to reduce the ID time of bipropellant DMAZ-WFNA. A drop-on-pool impingement set-up, coupled with a high-speed camera, was applied to investigate the ID time at ambient pressure and temperature. It was found that using of amines had dissimilar effects on the ID time of the bipropellant DMAZ-WFNA. Results showed that among the amines, pyrrole, tert-butylamine, n-octylamine reduced the ID time significantly. This study identified pyrrole as the most efficient “additive” for decreasing ID time (from 90 milliseconds to 20 milliseconds). Finally, a quantum molecular dynamics simulation was conducted to probe how the additive affects on the ID time.
      PubDate: 2017-11-16T09:50:26.351925-05:
      DOI: 10.1002/prep.201700208
       
  • A Safer Synthesis of 3,5-Bis(dinitromethyl)-1,2,4-triazole (BDT) and Its
           Mono and Di Salts: High-Performance Insensitive Energetic Materials
    • Authors: Srinivas Dharavath; Jean'ne M. Shreeve
      Abstract: Design and synthesis of new insensitive high-performance energetic materials are significant because of the demands of both civilian and military applications. Now a straightforward route which does not necessitate the use of 1,1-diamino-2,2-dinitroethene (FOX-7) as a starting material has been developed to synthesize 3,5-bis(dinitromethyl)-1,2,4-triazole (BDT) and its mono and dianion salts. The X-ray structure of bis- triaminoguanidinium 3,5-bis(dinitromethyl)-1,2,4-triazolate (10) further confirms the structure of this dianion. The gem dinitro carbon results in higher packing coefficients and extensive hydrogen bonding interactions. The experimental densities range from 1.66 to 1.93 g cm−3, detonation velocities from 8347 to 9086 ms−1, and pressures from 27.3 to 38.7 GPa, respectively. Some of these values are superior to those of current benchmark explosives, such as 1,3,5-trinitroperhydro-1,3,5-triazine (RDX).Energetic salts based on the 3,5-bis(dinitromethyl)-1,2,4-triazole monoanion and dianion were synthesized in a straightforward manner, without use of 1-diamino-2,2-diitroethene (FOX-7) as a starting material. The single-crystal X-ray structure of 10 shows extensive hydrogen bonding interactions. These findings provide new design thought for high performance energetic materials.
      PubDate: 2017-11-14T05:25:26.663318-05:
      DOI: 10.1002/prep.201700163
       
  • Facile Fabrication of Nanoparticles Stacked
           2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) Sub-microspheres via
           Electrospray Deposition
    • Authors: Chuan Huang; Jiahui Liu, Ling Ding, Dunju Wang, Zhijian Yang, Fude Nie
      Abstract: In this study, nanoparticles stacked 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) sub-microspheres were successfully fabricated by electrospray deposition. These monodisperse sub-microspheres with a diameter from 200–500 nm are composed of 50 nm nanoparticles, and after preserved six months these spheres retain the same structure and morphology. The effect of process parameter including flow rate and nozzle size on the size and morphology of sub-microsphere is investigated. The results show that, for a given solution concentration the nozzle size has little effect while the flow rate shows a significant effect. The X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) results exhibit that the as-prepared sub-microspheres have the same crystal and chemical structure as the raw materials. The thermal behavior performed by simultaneous thermal analysis (TG-DSC) verifies that in comparison to the raw materials sub-microspheres have a lower onset degradation temperature.
      PubDate: 2017-11-14T04:11:19.72351-05:0
      DOI: 10.1002/prep.201700154
       
  • Long-term Coarsening and Function-time Evolution of an Initiator Powder
    • Authors: Amitesh Maiti; Tammy Y. Olson, T. Yong Han, Richard H. Gee
      Abstract: Long-term effectiveness of high-explosive devices necessitates maintaining a level of specific surface area of initiating powder components within specified margins. This ensures that ignition and detonation performance of the powder does not degrade significantly over time. Flow permeametry is a commonly employed surface characterization tool in this context, as embodied in the Fisher sub-sieve surface area (FSSA). Recently we made alterations to the commercial permeametry apparatus that enables accurate in situ measurements of FSSA using only ∼100 mg samples. In this work we report on a 24-month aging study in such modified sample holders at elevated temperatures of 40 °C and 60 °C. Through a process called time-temperature-superposition (TTS) the resulting isotherms are translated into a single master curve that predicts powder FSSA evolution over decades under ambient temperature conditions. We generate master curves for two different powders, i. e., pure PETN and 1 wt% added TriPEON, and show that the TriPEON-doped powder coarsens at a rate a few times slower than the non-doped powder. Activation barriers computed from the TTS shift factors shed some light on the coarsening mechanisms.
      PubDate: 2017-11-13T06:35:30.373775-05:
      DOI: 10.1002/prep.201700186
       
  • Oblique Impacts and Friction of HMX and/or TATB-based PBXs
    • Authors: Didier Picart; Alexandra Junqua-Moullet
      Abstract: Transportation, handling, vibrations can lead to dynamic loadings requiring the characterization of the safety of plastic-bonded explosives (PBX). One of the addressed situations is the fall of explosive on a surface. Knowing that initiation can occur at a lower height during a vertical fall of a projectile on an inclined target than on a horizontal one, devices were developed to determine the critical thresholds. In this paper, data obtained on four HMX and/or TATB-based PBXs using pendulum drop configurations are detailed. Two analytical models are compared to estimate the heat released by friction at the interface. The model proposed in this paper yields the better agreement with data, and with finite element numerical simulations of the oblique impact on a given PBX. Lastly, the mechanical dissipation at the interface is estimated using this model and the simulations. This paper confirms that PBX/target friction cannot be the heating mechanism leading to initiation during oblique impacts.
      PubDate: 2017-11-10T04:46:47.347553-05:
      DOI: 10.1002/prep.201700184
       
  • Preparation, Characterisation and Performance of Microencapsulated Red
           Phosphorus
    • Authors: J. Liu; H. Guan
      Abstract: Microencapsuled red phosphorus (MRP), with a phenolic resin coating layer, was successfully prepared. It was characterized by Fourier-transform infrared spectroscopy (FTIR) and Scanning electron microscope (SEM). Meanwhile its water absorption, thermostability, thermodynamic properties and critical ignition temperature (Tb) have been studied. The results show that the MRP which is coated with phenolic resin can decrease the water absorption, increase thermostability and critical ignition temperature (Tb) significantly, compared with red phosphorus (RP). The thermodynamic properties which include apparent activation energy (E), pre-exponential factor (A), activation entropy (ΔS#), activation enthalpy (ΔH#) and Gibbs free energy (ΔG#) of RP and MRP are obtained. Moreover, the MRP can reduce the water absorption and friction sensitivity of red phosphorus smoke agent significantly with the best content of phenolic resin is 0.5 % or 1 %.
      PubDate: 2017-11-09T12:05:36.938436-05:
      DOI: 10.1002/prep.201700172
       
  • Study of the Elaboration of HMX and HMX Composites by the Spray Flash
           Evaporation Process
    • Authors: Vincent Pichot; Aymeric Seve, Jean-Edouard Berthe, Fabien Schnell, Denis Spitzer
      Abstract: 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.In composites containing HMX and TNT, the size of the particles strongly depends on the composition.
      PubDate: 2017-11-08T01:35:38.279084-05:
      DOI: 10.1002/prep.201700171
       
  • Synthesis and Investigation of the New Derivatives of
           Poly(Epichlorohydrin) Containing Energetic Groups
    • Authors: Fariborz Atabaki; Mohammad Hossein Keshavarz, Naser Noorollahy Bastam
      Abstract: In this research, poly(epichlorohydrin)(PECH) is modified by phenylhydrazine as well as 4-nitrophenylhydrazine and 2,4-dinitro phenylhydrazine. The chemical structures of the new derivatives of PECH are analyzed by Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR) and ultraviolet-visible (UV) techniques as well as carbon-hydrogen-nitrogen (CHN) ultimate analysis. Thermal characteristics of reaction products are studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Moreover, glass transition temperature (Tg) of these new polymers are determined. The results indicate that modifications of the poly(epichlorohydrin) are carried out successfully. The new energetic derivatives of PECH are good candidates for chemical industries, which may be considered as a novel class of energetic binders.
      PubDate: 2017-11-08T01:35:31.403994-05:
      DOI: 10.1002/prep.201700162
       
  • Synthetic Studies of 2,6-Diamino-3,5-Dinitropyrazine- 1-Oxide (LLM-105)
           from Discovery to Multi-Kilogram Scale
    • Authors: Philip Pagoria; Mao-Xi Zhang, Nathaniel Zuckerman, Gregory Lee, Alexander Mitchell, Alan DeHope, Alexander Gash, Clifford Coon, Patrick Gallagher
      Abstract: A description of the various approaches to the synthesis of the insensitive energetic compound, 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105), developed at LLNL over the past 20 years will be described.
      PubDate: 2017-11-03T08:16:19.529499-05:
      DOI: 10.1002/prep.201700182
       
  • A Mechanism of Hot-spots Formation at the Crack Tip of Al-PTFE under
           Quasi-static Compression
    • Authors: Bin Feng; Yu-chun Li, Hong Hao, Huai-xi Wang, Yi-fei Hao, Xiang Fang
      Abstract: Generally, the Al-PTFE (polytetrafluoroethylene) is thought to be inert under quasi-static or static loads. However, it was found that Al-PTFE would initiate under quasi-static compression after a specific heat treatment procedure and the opening fracture plays a crucial role in the initiation. A unique micrographic fracture pattern which showed unstable crack propagation and a ductile-to-brittle transition was observed at openning cracks by SEM. Combining the observed microstructure with the stress distribution at the path of crack propagation derived from numerical simulation, a mechanism was proposed to explain the formation of “hot-spots” at the crack tip. The temperature rise at the crack tip was estimated to be at least 612 °C, which is high enough to ignite the Al-PTFE composite.
      PubDate: 2017-11-03T07:20:49.189681-05:
      DOI: 10.1002/prep.201700106
       
  • High-Fidelity Microstructural Characterization and Performance Modeling of
           Aluminized Composite Propellant
    • Authors: Graham D. Kosiba; Ryan R. Wixom, Matthew A. Oehlschlaeger
      Abstract: Image processing and stereological techniques were used to characterize the heterogeneity of composite propellant and inform a predictive burn rate model. Composite propellant samples made up of ammonium perchlorate (AP), hydroxyl-terminated polybutadiene (HTPB), and aluminum (Al) were faced with an ion mill and imaged with a scanning electron microscope (SEM) and x-ray tomography (micro-CT). Properties of both the bulk and individual components of the composite propellant were determined from a variety of image processing tools. An algebraic model, based on the improved Beckstead-Derr-Price model developed by Cohen and Strand, was used to predict the steady-state burning of the aluminized composite propellant. In the presented model the presence of aluminum particles within the propellant was introduced. The thermal effects of aluminum particles are accounted for at the solid-gas propellant surface interface and aluminum combustion is considered in the gas phase using a single global reaction. Properties derived from image processing were used directly as model inputs, leading to a sample-specific predictive combustion model.
      PubDate: 2017-10-27T06:16:02.347654-05:
      DOI: 10.1002/prep.201700124
       
  • Highly Thermal Stable TATB-based Aluminized Explosives Realizing Optimized
           Balance between Thermal Stability and Detonation Performance
    • Authors: Feiyan Gong; Hu Guo, Jianhu Zhang, Chunying Shen, Congmei Lin, Chengcheng Zeng, Shijun Liu
      Abstract: In this work, a series of TATB-based aluminized explosives were formulated from 1, 3, 5-triamino-2, 4, 6-trinitrobenzene (TATB), aluminum powders and polymeric binders. The thermal stability, heat of detonation, detonation velocity and pressure of the TATB based aluminized (TATB/Al) explosives were systematically investigated by cook-off, constant temperature calorimeter, electrometric method and manganin piezo resistance gauge, respectively. The selected PBX-3 (70 wt% TATB/25 wt% Al/5 wt% fluorine resin) achieved optimized balance between thermal stability and detonation performance, with the thermal runaway temperature around 583 K. The thermal ignition of TATB-based aluminized explosive occurred at the edge of the cylinder according to the experimental and numerical simulations. Moreover, the critical thermal runaway temperature for PBX-3 was calculated based on the Semenov's thermal explosion theory and the thermal decomposition kinetic parameters of the explosive, which was consistent with the experimental value.The high thermal runaway temperature (approximately 583 K), mild reaction degree, slight dependence of runaway temperature on the explosive sizes and high detonation performance of PBX-3 (70 wt% TATB/25 wt% Al/5 wt% fluorine resin) demonstrated excellent balance between thermal stability and detonation performance of TATB-based aluminized explosives.
      PubDate: 2017-10-26T03:50:37.77512-05:0
      DOI: 10.1002/prep.201700206
       
  • Nitrate Salt Based Melt Cast Materials
    • Authors: Philip W. Leonard; David E. Chavez, Patrick R. Bowden, Elizabeth G. Francois
      Abstract: Three new low melting compositions have been developed based on the ingredients amino-1,2,4-triazolium nitrate, 3,5-diamino-1,2,4-triazolium nitrate and ammonium nitrate, to create the formulation AAD, in addition to mixtures comprising guanidinium 5-amino-tetrazolate and ammonium nitrate in either a 1 : 3 or 1 : 6 mole ratio (GAN13 and GAN16 respectively). The materials melt in the range of 95–100 °C and do not begin to decompose until >195 °C. The formulations are insensitive to impact, spark and friction and were calculated to show promising explosive performance properties (VD=8.78–9.0 km/s, PCJ=28.4–30.6 GPa). HMX mixtures of AAD, GAN13 and GAN16 were also prepared and these materials were characterized with respect to their safety and performance as well.
      PubDate: 2017-10-24T06:25:08.143678-05:
      DOI: 10.1002/prep.201700183
       
  • Novel Nitrogen-Rich Tetrazine-Based High Energy Density Molecules:
           Molecular Design and Computational Studies
    • Authors: Rudraditya Sarkar; Daradi Baishya, Divya Mahendhiran, Raja K. Rit
      Abstract: The molecular structure, thermal stability, detonation properties and impact sensitivity of nitrogen-rich tetrazine-based designed high energy density molecules are examined. The effective stability of the designed molecules in terms of electronic structure, thermal excitation, photo-excitation and in presence of water are predicted. The topography of the excited and ground state (S1 and S0) of those molecules along the C−NO2 bond dissociation coordinate are studied. The existence of the double minima at the S1 state and the S1-S0 intersection produces a probabilistic path for molecules B1, B2 and A1, to revert back to their respective S0 state from the S1 state via both radiative and non-radiative deactivation mechanism. The energy content (in terms of heats of formation), detonation velocities and detonation pressure of tetrazine-based molecules are measured. Interestingly, the thermal stability of these designed molecules is higher than the two well-known high energy density molecules: RDX and HMX. The detonation velocities and the detonation pressure of these molecules are higher than RDX, however, are lower than HMX. In addition, the safety, reliability and stability of these high energy density molecules have been measured by formulating semi-empirical equations of impact sensitivity based on linear and multiple linear regression method and the present study is ended with the discussion of most probable synthetic routes to the designed molecules.A detailed computational studies have been performed to understand the molecular topology, thermal and effective stability, energy content, detonation properties and impact sensitivity of newly designed nitrogen-rich tetrazine-based high energy density molecules. Interestingly, some of the designed molecules display promising result in terms of thermal stability and detonation properties in comparison to two well-known high energy density molecules: RDX and HMX.
      PubDate: 2017-10-24T06:25:02.5986-05:00
      DOI: 10.1002/prep.201700156
       
  • A Low-Sensitivity Composition Based on FOX-7
    • Authors: Amel Belaada; Waldemar A. Trzciński, Zbigniew Chyłek, Józef Paszula
      Abstract: 1,1-Diamino-2,2-dinitroethene (DADNE, FOX-7) is considered to be an explosive combining comparatively high performance and low sensitivity. In the present study, FOX-7 has been evaluated as a possible replacement of RDX in TNT-based melt-cast compositions. A composition containing FOX-7, TNT, Al and wax, and a method of preparing it were proposed. Its sensitivity to impact, friction, shock wave, jet impact, fast heating, and its thermal stability were tested. Some detonation parameters like the detonation pressure, velocity and heat were measured. Moreover, the Gurney velocity, the so-called effective exponent of the expansion isentrope and the JWL equation of state of the detonation products were determined from the results of a cylinder test. The detonation characteristics were compared with that obtained for cast TNT.
      PubDate: 2017-10-18T06:30:30.175851-05:
      DOI: 10.1002/prep.201700149
       
  • Nitrocellulose Synthesis from Miscanthus Cellulose
    • Authors: Yulia A. Gismatulina; Vera V. Budaeva, Gennady V. Sakovich
      Abstract: The possibility of synthesizing nitrocellulose (NC) from an easily renewable non-woody feedstock, Miscanthus, is demonstrated herein. Nitration of Miscanthus cellulose with commercial mixed acid was found to afford high-quality NC: 11.85 % nitrogen content, 18 cP viscosity of 2 % NC-acetone solution, 97 % solubility in alcohol-ester mixture, and 0.11 % ash content. The Miscanthus NC structure and fibers were characterized by analytical techniques such as SEM, IR spectroscopy, TGA/DTG, and 13C NMR spectroscopy. The Miscanthus NC is comparable in quality to basic NC types used for the manufacture of films, membranes, lacquers, nail polish, liquid bandage, artificial silk and skin.Photo of Miscanthus NC burning in a fume hood
      PubDate: 2017-10-17T06:50:28.228425-05:
      DOI: 10.1002/prep.201700210
       
  • Effects of Aluminum Particle Size on the Detonation Pressure of TNT/Al
    • Authors: Zhengqing Zhou; Jianguo Chen, Hongyong Yuan, Jianxin Nie
      Abstract: To better understand the influence of the aluminum particle size on the detonation pressure of TNT/Al, electrical conductivity experiment and detonation pressure experiment were performed in this study. Four types of TNT/Al were considered, in which the particle size of aluminum was 50 nm, 100 nm, 1.50 μm, and 9.79 μm, respectively. The combustion process of Al in TNT/Al was detected by electrical conductivity experiment, and the detonation pressures of TNT/Al were measured by using the manganin pressure sensors. According to the experimental results, the Chapman Jouguet (CJ) pressure of the explosive containing nano-sized aluminum is higher than the explosive containing micron-sized aluminum powder because of the combustion of nano-sized aluminum in the detonation reaction zone. In addition, a smaller aluminum particle size in TNT/Al is associated with a slower detonation pressure attenuation. This study gives a clearer picture of how aluminum particle size contributes to detonation pressure on timescales from 0 to 0.82 μs.
      PubDate: 2017-10-13T02:55:37.92118-05:0
      DOI: 10.1002/prep.201700109
       
  • In-Situ Tensile Testing of Propellants in SEM: Influence of Temperature
    • Authors: Giuseppe L. Di Benedetto; Marthinus C. J. van Ramshorst, Willem Duvalois, Peter A. Hooijmeijer, Antoine E. D. M. van der Heijden
      Abstract: A tensile module system placed within a Scanning Electron Microscope (SEM) was utilized to conduct in-situ tensile testing of propellant samples. The tensile module system allows for real-time in-situ SEM analysis of the samples to determine the failure mechanism of the propellant material under tensile force. The focus of this study was to vary the experimental parameters of the tensile module system and analyze how they affect the failure mechanism of the samples. The experimental parameters varied included strain rate and sample temperature (−54, +25 and +40 °C). Stress-strain diagrams were recorded during the in-situ tensile tests, and these results were coupled with the in-situ images and videos of the samples captured with SEM analysis. The experiments conducted at −54 °C showed a different failure behavior of the propellant sample due to its rigidity at this low temperature, while experiments conducted at +25 and +40 °C displayed a similar failure mechanism. For future testing using this tensile tester, special attention should be given to improved temperature control of the specimen, especially at low temperatures.
      PubDate: 2017-10-12T01:10:24.817622-05:
      DOI: 10.1002/prep.201700178
       
  • Thermal Behavior and Decomposition Kinetics of
           Bis(2,2,2-trinitroethyl)-oxalate as a High Energy Dense Oxidizer and its
           Mixture with Nitrocellulose
    • Authors: Mohamed Abd-Elghany; Thomas M. Klapötke, Ahmed Elbeih
      Abstract: A new propellant formulation (NC-BTNEOx) based on bis(2,2,2-trinitroethyl)oxalate (BTNEOx) as a high energy dense oxidizer (HEDO) mixed with nitrocellulose (NC) matrix was prepared and studied. BTNEOx was prepared and characterized by nuclear magnetic resonance (NMR) and X-ray diffraction (XRD). Photos of the prepared formulation obtained by scanning electron microscope (SEM) clarified a good mixing of the nitrocellulose (NC) matrix with BTNEOx. A smokeless burning was observed and recorded for the prepared NC-BTNEOx by a high speed camera. The thermal behavior and decomposition kinetics of the NC matrix, BTNEOx and their mixture have been investigated nonisothermally by using thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC). Isoconversional (model-free) methods; Kissinger, Ozawa and Flynn−Wall (OFW) and Kissinger−Akahira−Sunose (KAS), were used to determine the kinetic parameters of the studied samples. The results proved that BTNEOx has melting temperature at 104.1 °C and maximum peak temperature at 200.6 °C, also it has effective activation energy in the range of 107–110 kJ/mol. The prepared NC-BTNEOx has no endothermic peak and has exothermic peak at 201.7 °C which means that a composite might be formed due to the mixing of BTNEOx with NC. The prepared NC-BTNEOx has effective activation energy in the range of 172–180 kJ/mol. BTNEOx required more study to proof the possibility of replacing the nitroglycerine in a smokeless double base propellant.
      PubDate: 2017-10-10T04:40:59.014562-05:
      DOI: 10.1002/prep.201700179
       
  • A Review of Illuminating Pyrotechnics
    • Authors: Jesse J. Sabatini
      Abstract: This review article consists of efforts focused on the development of illuminating pyrotechnics. Examined will be the methods of generating red-, green-, yellow- and blue-light-emitting illuminating pyrotechnics. Ways to improve luminosity, spectral purity, and burn rate will be discussed. Recently developed formulations concerning the development of environmentally friendly illuminating pyrotechnics will also be presented.This review article concerns the development of illuminating pyrotechnics. Examined will be the methods of generating red-, green-, yellow- and blue-light-emitting illuminating pyrotechnics. Ways to improve luminosity, spectral purity, and burn rate will be discussed.
      PubDate: 2017-10-05T03:35:33.805199-05:
      DOI: 10.1002/prep.201700189
       
  • Effect of Crystal Quality and Particle Size of HMX on the Creep Resistance
           for TATB/HMX Composites
    • Authors: Congmei Lin; Jiahui Liu, Guansong He, Zhijian Yang, Liping Pan, Shijun Liu, Jiang Li, Shaoyun Guo
      Abstract: Two kinds of reduced sensitivity high explosive 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (RS-HMX) with different particle sizes were selected to enhance the energy output and the mechanical properties of insensitive high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Mechanical sensitivities, dynamic mechanical analysis, and non-linear time dependent creep behaviors of TATB/HMX composites were investigated and discussed in relation to the structural characteristics. Compared with TATB/conventional HMX (C-HMX) sample, both the impact and friction sensitivities of TATB/RS-HMX were reduced. It revealed that TATB/fine grains RS-HMX composites had the highest storage modulus and minimum steady-state creep strain rate due to the increased coherence strength and the inhibited slide of the single layer of TATB crystal. The creep resistance also showed clear dependence on the particle size of RS-HMX. The overall results indicated that RS-HMX had good potential in high energetic, safe, and load-bearing material applications.
      PubDate: 2017-09-19T06:05:40.449053-05:
      DOI: 10.1002/prep.201700153
       
  • Formation and Characterization of Heavy Alkali and Silver Salts of the
           4-Nitro-pyrazolo-(3,4-c)-furazan-5-N-oxide Anion
    • Authors: Tobias S. Hermann; Thomas M. Klapötke, Burkhard Krumm
      Abstract: The nitration of 3-amino-4-chloro-oximidofurazan resulted in the formation of the unexpected anionic heterocycle 4-nitro-pyrazolo-(3,4,c)-furazan-5-N-oxide. Various experiments such as changing the reactants, oxidation or methylation were attempted to elucidate the reaction conditions and mechanism. The heavier alkali and silver salts of the above-mentioned heterocycle were isolated. The salts were characterized and investigated by means of NMR, vibrational spectroscopy, X-ray diffraction and energetic properties.The highly energetic nitro-pyrazolo-(3,4-c)-furazan-5-N-oxide anion was obtained and characterized. Its heavy alkali metal and silver salts show high sensitivities toward impact and friction.
      PubDate: 2017-09-18T05:00:28.28025-05:0
      DOI: 10.1002/prep.201700170
       
  • Thermal Behavior and Specific Heat Capacity of
           1-t-Butyl-3,3-dinitroazetidinium Perchlorate
    • Authors: Biao Yan; Hongya Li, Yulei Guan, Haixia Ma, Jirong Song, Fengqi Zhao
      Abstract: 1-t-Butyl-3,3-dinitroazetidinium perchlorate (TDNAZ ⋅ HClO4) was synthesized, DSC and TG/DTG methods were used to study the thermal behavior of TDNAZ⋅HClO4 under a non–isothermal condition. The intense exothermic decomposition process of DSC curves were analyzed to obtain its kinetic parameters. Continuous specific heat capacity (Cp) mode of micro–calorimeter was used to determine its Cp, its specific molar heat capacity (Cp,m) was 365.70 J mol−1 K−1 at 298.15 K. The self-accelerating decomposition temperature (TSADT), thermal ignition temperature (TTIT), and critical temperature of thermal explosion (Tb) were obtained to evaluate its thermal stability and safety. The above results of TDNAZ ⋅ HClO4 were compared with those of 3,3-dinitroazetidinium perchlorate (DNAZ ⋅ HClO4), and the effect of tert-butyl group on them was discussed.DSC and TG/DTG methods were used to study the thermal behavior of TDNAZ⋅HClO4. The analysis showed that the tert-butyl group improved the thermal stability and safety of compound, and reduced the decomposition heat and lattice energy of compound. The Cp,m of TDNAZ ⋅ HClO4 is 365.70 J mol−1 K−1 at 298.15 K. The results showed that tert-butyl group had remarkable contribution to ΔCp,m.
      PubDate: 2017-09-11T09:50:07.433692-05:
      DOI: 10.1002/prep.201700125
       
  • Synthesis and Characterization of New Melt-cast Energetic Salts:
           Dipotassium and Diaminoguanidinium
           
    • Authors: Qing Ma; Hao Gu, Jinglun Huang, Dabin Liu, Jinshan Li, Guijuan Fan
      Abstract: Diaminoguanidinium N,N′-dinitro-N,N′-bis(3-dinitromethyl-furazanate-4-yl)methylenediamine (5), a new melt-cast energetic salt, was designed and synthesized via metathesis reaction from dipotassium N,N′-dinitro-N,N′-bis(3-dinitromethyl-furazanate-4-yl)methylenediamine (4) by using condensation of 3-amino-4-chloroximinofurazan (1), followed by a mixture of fuming nitric acid and trifluoroacetic anhydride and then KI reduction. The target products were thoroughly characterized by NMR spectroscopy, vibrational spectroscopy (IR), elementary analysis, and differential scanning calorimetry (DSC). Single-crystal X-ray diffraction was employed for analyzing the crystal structure of 5. Compound 4 not only exhibits two-stages in decomposition properties but also behaves sensitivities as primary explosive (IS: 2.5 J, FS: 216 N). Compound 5 exhibits excellent thermal stability (onset m.p. 113 °C, onset dec. 282 °C) which is superior to those of RDX and approach those of TNT. Different from RDX, 5 exhibits better impact and friction sensitivity (IS: 20 J, FS: 128 N). Worth noting that, the detonation velocity of 5 (D: 8500 m s−1) is comparable with that of RDX.New high-performance melt-cast energetic salts featuring gem-dinitro moiety and close-chain nitramine groups based on furazan backbones were synthesized and fully characterized. Their physicochemical properties were also investigated.
      PubDate: 2017-08-28T05:07:23.310444-05:
      DOI: 10.1002/prep.201700164
       
  • Detonation Performance Characterization of a Novel CL-20 Cocrystal Using
           Microwave Interferometry
    • Authors: Vasant S. Vuppuluri; Philip J. Samuels, Kelley C. Caflin, I. Emre Gunduz, Steven F. Son
      Abstract: Development of novel energetic materials is a significant challenge. Cocrystallization has been explored as another route to development of novel materials. However, very little characterization of detonation performance has been performed for these energetic cocrystals. A major challenge for performing detonation velocity measurements with cocrystals is that typical measurement techniques require hundreds of grams to kilograms of material, an amount that exceeds the entire supply of many cocrystals. In this work, small-scale detonation velocity measurements using about 1.2 g of material per test employing microwave interferometry are presented and discussed for a novel cocrystal of 1-methyl-3,5-dinitro-1,2,4-triazole (MDNT) and hexanitrohexaazaisowurtzitane (CL-20) in a 1 : 1 molar ratio and compared to a physical mixture of MDNT and CL-20 in the same molar ratio. The results are compared with detonation velocity measurements with cyclotetramethylene tetranitramine (HMX), which provide validation of the technique and further comparison of the results. With this technique, detonation velocity differences as low as 100 m/s are resolvable. The MDNT/CL-20 cocrystal is observed to detonate over 500 m/s faster than the physical mix and over 600 m/s faster than HMX at the same charge density which is held constant in this work. The enthalpy of formation of the MDNT/CL-20 cocrystal was also measured. Using this, the detonation velocity of the cocrystal was calculated using thermochemistry to be 230 m/s faster than that of the physical mixture of MDNT and CL-20 in the same molar ratio as is contained within the cocrystal at a charge density of 1.4 g/cm3. The higher detonation velocity of the cocrystal (both measured and predicted) compared to the physical mixture is likely attributable to bonding energy contained within the cocrystal and the arrangement of the coformers within the cocrystal.
      PubDate: 2017-08-07T04:40:36.301305-05:
      DOI: 10.1002/prep.201700150
       
  • Crystal Structure, Thermal Behavior and Detonation Characterization of
           Bis(3,3-dinitroazetidin-1-yl)methane
    • Authors: Biao Yan; Hongya Li, Yulei Guan, Haixia Ma, Jirong Song, Fengqi Zhao
      Abstract: Bis(3,3-dinitroazetidin-1-yl)methane (BDNAZM) was synthesized and the crystal structure was determined by a X-ray diffraction. It belongs to monoclinic system with space group P21/n. Its thermal behavior and non-isothermal decomposition kinetics were studied with DSC and TG/DTG methods. The self-accelerating decomposition temperature (TSADT), thermal ignition temperature (TTIT), and critical temperature of thermal explosion (Tb) are 141.06 °C, 154.15 °C and 160.62 °C, respectively. BDNAZM has a low melting point (86.82 °C), and it has higher detonation velocity (7217 ms−1) and detonation pressure (22.0 GPa) than these of TNT.BDNAZM belongs to monoclinic system with space group P21/n. The self-accelerating decomposition temperature, thermal ignition temperature, and critical temperature of thermal explosion are 141.06 °C, 154.15 °C and 160.62 °C, respectively. It has a low melting point (86.82 °C), and it has higher detonation velocity (7217 ms−1) and detonation pressure (22.0 GPa) than these of TNT.
      PubDate: 2017-06-13T08:01:08.858677-05:
      DOI: 10.1002/prep.201700088
       
  • Cover Picture: Influence of Particle Size on the Combustion of CL-20/HTPB
           Propellants (Prop., Explos., Pyrotech. 11/2017)
    • Authors: Joseph Kalman; Jonathan Essel
      Pages: 1239 - 1239
      Abstract: The cover picture shows data of a CL-20/HTPB propellant before, during, and after combustion. The size dependence of CL-20 was investigated for particles ranging from 100 μm to several hundred nanometers in diameter. The structure of the solid combustion residue shown became more structured at lower pressures and smaller particle sizes providing insight into the combustion mechanism. It was determined that the large particle formulation was dominated by a monopropellant flame while the smaller particle propellants were driven by passive and active cooling. More details can be found in the Full Paper by J. Kalman and J. Essel on page 1261 ff.
      PubDate: 2017-11-23T09:12:54.287623-05:
      DOI: 10.1002/prep.201781101
       
  • Inside Cover: Preparation and Characterization of Nanoenergetics Based
           Composition B (Prop., Explos., Pyrotech. 11/2017)
    • Authors: Hongwei Qiu; Victor Stepanov, Rajen B. Patel, Philip Samuels, Katherine H. Maier
      Pages: 1240 - 1240
      Abstract: The inside cover picture shows the preparation of nanoenergetics-based Comp B (N-Comp B) by spray drying and mechanical compaction. Spray drying previously has been proven to be a facile materials processing method for the preparation of nanoscale crystals of high explosives (i.e., nanoenergetics)-based formulations (H. Qiu et al., J. Hazard. Mater. 2011, 185, 489–493). In this work, N-Comp B, which consists of nanoscale RDX and TNT, was produced by compacting the molding powder prepared by spray drying an acetone solution of RDX and TNT. Reduced shock sensitivity was observed from N-Comp B, attributed to the elimination of large voids, but the decrease seems to have been limited by the presence of a large number of voids. Thermal cycling induced significant structural change, i.e., the increase of both void size and the crystal size, causing an increase in sensitivity. Procedures are proposed to further reduce the sensitivity and enhance the thermal stability of N-Comp B. This work continues to demonstrate the versatility of spray drying for nanoenergetics. Furthermore, it illustrates that a materials science-based approach can facilitate the development of next generation explosives with high performance and low sensitivity. More details can be found in the Full Paper by Hongwei Qiu et al. on page 1309 ff.
      PubDate: 2017-11-23T09:12:54.33181-05:0
      DOI: 10.1002/prep.201781102
       
  • Contents: Prop., Explos., Pyrotech. 11/2017
    • Pages: 1241 - 1243
      PubDate: 2017-11-23T09:12:51.041162-05:
      DOI: 10.1002/prep.201781111
       
  • A New Insight to the Color Change Phenomenon of TATB: Structural Color
    • Authors: Xianqing Tian; Xinfeng Wang, Kun Yu, Jie Sun, Dan Xiao
      Pages: 1247 - 1251
      Abstract: The color change phenomenon of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) has puzzled the energetic researchers for decades. Many efforts have been dedicated to identifying the “colored TATB”, however, hardly any of well-established evidences have been ascertained. After detailed reviewing the literatures, we herein propose a new insight to survey the coloration of TATB. And a 3D photonic crystal model has been proposed to elucidate the color change phenomenon of TATB. Coloration behavior of the TATB is confirmed by home-made TATB thin film. It is proved that the coloration of TATB is a physical appearance, structural color.
      PubDate: 2017-10-04T05:10:49.698652-05:
      DOI: 10.1002/prep.201700128
       
  • Effects of an Organic-inorganic Nanocomposite Additive on the Combustion
           and Erosion Performance of High Energy Propellants Containing RDX
    • Authors: Na Sun; Zhenggang Xiao
      Pages: 1252 - 1260
      Abstract: 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.
      PubDate: 2017-08-24T13:00:41.524351-05:
      DOI: 10.1002/prep.201700155
       
  • Influence of Particle Size on the Combustion of CL-20/HTPB Propellants
    • Authors: Joseph Kalman; Jonathan Essel
      Pages: 1261 - 1267
      Abstract: The effect of nitramine particle size on the combustion behavior of inert binder based propellants has been extensively studied for RDX and HMX, but not CL-20. Although materials such as RDX and HMX are useful for particular combustion applications, CL-20 has a greater potential to improve the oxygen balance and energy density of a propellant. The current work investigates the effect of CL-20 particle size on the combustion of CL-20/HTPB propellants down to submicrometer sizes. An influence of particle size on the burning rate and combustion mechanism is reported. The 30 micrometer formulation burning rate data showed evidence of convective burning specifically at higher pressures, but the pressure dependence was comparable to neat CL-20 at pressures below 8 MPa. A change in the combustion mechanism of the submicrometer formulation as a function of pressure was determined to be a result of the interaction of the propellant flame and the combustion residue. Data suggested that at low pressures diffusion in terms of active cooling was dominant for the submicrometer formulation. Higher pressure data for both the submicrometer and 3 micrometer formulations suggest the degree of active cooling is decreased as the burning rate pressure exponent is near 0.5 for both propellants. The indirect evidence for the presence of a melt layer for CL-20 propellants is discussed.
      PubDate: 2017-09-12T07:41:37.279162-05:
      DOI: 10.1002/prep.201700137
       
  • Mechanical Modifications of Paraffin-based Fuels and the Effects on
           Combustion Performance
    • Authors: Yue Tang; Suhang Chen, Wei Zhang, Ruiqi Shen, Luigi T. DeLuca, Yinghua Ye
      Pages: 1268 - 1277
      Abstract: In order to enhance the mechanical properties, 6 kinds of additives of stearic acid, polyethylene wax (A−C®6A), ethylene vinyl acetate copolymer (EVA), low density polyethylene (LDPE), polypropylene (PP) and high density polyethylene (HDPE) were blended in the paraffin fuel. Mechanical properties of paraffin-based fuels were investigated by mixing 5 % in mass of different additives and increasing the mass percent of A−C®6A and LDPE. In addition, the combustion performance of the so modified paraffin-based fuels were tested by a 2D-radial burner at Nanjing University of Science and Technology. The effects of additives on regression rate were analyzed by thermal performance test (melting point and DSC) and viscosity measurement. Overall, all the additives can improve mechanical properties and the mechanical properties are enhanced by increasing mass% of additives. A−C®6A revealed the best for improving compressive strength (64.0 % increase by blending 5 mass %), LDPE revealed the best for improving tensile strength (105.3 % increase by blending 5 mass %). For combustion performance, the regression rates of paraffin-based fuels blended with stearic acid increased owing to the decreased melting points while the regression rates of the other five formulations decreased due to the increased melted liquid viscosity. The relationship between regression rate and viscosity is a power function which is not affected by additives at high temperature, thereby it is convenient to predict the regression rate by measuring viscosity.
      PubDate: 2017-09-07T07:41:43.549991-05:
      DOI: 10.1002/prep.201700136
       
  • Preliminary Study of New Propellants Containing Guanidinium or
           Triaminoguanidinium Azotetrazolate
    • Authors: Mateusz Szala; Marcin Hara, Leszek Szymańczyk, Zbigniew Surma
      Pages: 1278 - 1282
      Abstract: 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.
      PubDate: 2017-09-04T02:05:22.558263-05:
      DOI: 10.1002/prep.201700090
       
  • Mechanical Characteristics and Thermal Decomposition Behaviors of
           Polytetrahydrofuran Binder with Glycerol Propoxylate (Mn=1500) as a
           Crosslinking Agent
    • Authors: Makoto Kohga
      Pages: 1283 - 1288
      Abstract: Polytetrahydrofuran (PTHF) is an effective binder ingredient for improving propellant performance, although it is not an energetic material. PTHF becomes sufficiently rubbery for use as a binder when a triol is added as a crosslinking modifier. In this study, glycerol propoxylate (GPO), with a molecular weight of 1500, was used as a crosslinking modifier, and the curing behavior, tensile properties, and thermal decomposition behaviors of the PTHF binder with GPO were investigated. A PTHF (Mn=650)/GPO blend with a PTHF/GPO mole ratio (ξ) less than or equal to 4 and a PTHF (Mn=1400)/GPO blend with ξ≤1 were used as propellant binders. The curing behaviors and mechanical properties of the PTHF/GPO blends were influenced by the molecular weight of PTHF and ξ, while the thermal decomposition behaviors were not affected. It was found that the PTHF/GPO blends had higher initial viscosity, longer pot life, and unique mechanical properties compared to those of the PTHF blends supplemented with GPO (Mn=260).
      PubDate: 2017-09-04T06:32:12.11887-05:0
      DOI: 10.1002/prep.201700143
       
  • Measurement and Modelling of Pyrotechnic Time Delay Burning Rates:
           Application and Prediction of a Fast Burning Delay Composition
    • Authors: Yolandi C. Montgomery; Walter W. Focke, Cheryl Kelly
      Pages: 1289 - 1295
      Abstract: A predictive numerical model was implemented for a time delay based on the Si+Pb3O4 system. The reaction kinetic parameters were estimated by comparing predicted surface temperature profiles with experimental data acquired with an infrared camera. Fair agreement between the modelled and measured burning rates was achieved. The burning rate is predicted to increase by 9.4 % for every 50 °C increase in ambient temperature. The core diameter was found to have a slightly larger impact on the burning rate than the wall thickness. The effect of using different wall thickness materials was evaluated and indicated that the burning rate is significantly influenced by the wall material when the thermal conductivity is increased and the volumetric heat capacity is reduced. The shape of the combustion front was found to widen with a long tail for materials with a low thermal conductivity and a narrower combustion front with a short tail for materials with high thermal conductivity. Preheating occurred for pyrolytic graphite- and diamond-based elements but no radial combustion was observed. The external heat transfer parameters (convection and radiation) did not affect the burning rate of the fast delay composition. It is concluded that the ambient temperature, volume fraction solids, molar heat of reaction, core and outer diameter are the factors that most significantly influence the burning rate of the Si+Pb3O4 composition in long cylindrical elements.
      PubDate: 2017-07-18T02:30:38.061527-05:
      DOI: 10.1002/prep.201700105
       
  • New Application of Hydroxyl Groups: Ligands for High Density Metal Organic
           Frameworks
    • Authors: Hui Su; Yalu Dong, Yao Du, Pengcheng Zhang, Panpan Peng, Shenghua Li, Jichuan Zhang, Siping Pang
      Pages: 1296 - 1302
      Abstract: Energetic metal organic frameworks (MOFs) with energetic anions as ligands can be used as new-generation explosives. Many powerful anions have been introduced into energetic MOFs to improve the properties; however, the hydroxyl as a common group for energetic MOFs has rarely been studied. In this article, we present two examples of energetic MOFs ([Cu(atz)(NO3)(OH)]n) and [Zn(ata)(OH)] (atz=4-amino-1,2,4-triazole; ata=5-amino-1H-tetrazole) with the hydroxyl group as the ligand. Crystal structure analyses reveal that the two compounds possess compact two-dimensional (2-D) structures with densities up to 2.41 g cm−3 and 2.54 g cm−3, respectively. These two compounds have excellent physicochemical properties. The results demonstrate that a hydroxyl group as the ligands could commendably increase the densities of energetic MOFs, thereby enhancing the detonation performance. It is anticipated this work will open a new direction for the development of energetic MOFs.
      PubDate: 2017-10-02T01:40:25.413933-05:
      DOI: 10.1002/prep.201700101
       
  • Hot Spot Formation in Mock Materials in Impact Sensitivity Testing by Drop
           Hammer
    • Authors: John G. Reynolds; Peter C. Hsu, Gary A. Hust, Stephen A. Strout, H. Keo Springer
      Pages: 1303 - 1308
      Abstract: Powder and granulated sugars were exposed to the drop hammer impact test configured with 120- and 180-grit Si/C sandpapers. The sugars were selected as mock materials for HMX (Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine). The drop heights ranged from 24.2 to 40.7 cm. Samples were examined by visible microscopy before and after testing and the appearance of yellow and brown discolorations in the spent samples were assigned as hot spots. These discolorations were divided into two types; those collocated with grit particles and those that were not. Hot spots are found in the spent samples in almost every test condition. Powder sugar appears to be more active in producing hot spots than the granulated sugar based on comparisons at identical conditions. Drop height, within this specific range, has little effect on the formation of hot spots, except for 40.7 cm high-end limit, which causes a dramatic increase in spot formation. The predominant hot spot type formed is collocated with grit particles, suggesting association of hot spot formation due to grit, something that has been discussed in previous treaties. Foreign objects were also observed, some imbedded and some not imbedded. Discoloration was not observed around these sites, suggesting these types of foreign materials are not responsible for hot spot formation, at least under these conditions. Grit associated with a visible tail was observed in some instances, suggesting that grit can be quite mobile through the sample when the pressure is applied by the drop weight (through the striker).
      PubDate: 2017-08-25T04:39:47.071927-05:
      DOI: 10.1002/prep.201700115
       
  • Preparation and Characterization of Nanoenergetics Based Composition B
    • Authors: Hongwei Qiu; Victor Stepanov, Rajen B. Patel, Philip Samuels, Katherine H. Maier
      Pages: 1309 - 1314
      Abstract: Explosive compositions employing nanoscale crystals of high explosives (i. e., nanoenergetics) have demonstrated reduced sensitivities to external stimuli. Until recently, the investigated formulations were limited to plastic bonded explosives. Explosives that are normally melt-cast also would benefit from the use of nanoenergetics. However, the integration of nanoenergetics into the melt-cast process is challenging due to the large surface area and solubility associated with nanoenergetics. In this work, we explored the preparation of nanoenergetics-based Composition B (Comp B), a widely used melt-cast explosive, by spray drying followed by mechanical compaction. The Comp B molding powder obtained from spray drying was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The structure and the shock sensitivity of the compacted nanoenergetics-based Comp B (N-Comp B), both as-prepared and thermally cycled, was also studied using melt-cast Comp B as the reference material. The characterization shows that N-Comp B consisting of nanoscale cyclotrimethylenetrinitramine (RDX) and trinitrotoluene (TNT) contains mostly nanoscale voids but has a large number density. Reduced shock sensitivity was observed from N-Comp B, attributed to the elimination of large voids. But the decrease seems to have been constrained by the large number density of voids. Thermal cycling induced significant structural change, i. e., the increase of both void size and the crystal size, causing an increase in sensitivity. Procedures are proposed to further reduce the sensitivity and enhance the thermal stability of N-Comp B.
      PubDate: 2017-08-10T06:10:42.015407-05:
      DOI: 10.1002/prep.201700165
       
  • Effect of Mixing Methods on the Thermal Stability and Detonation
           Characteristics of Ammonium Nitrate and Sodium Chloride Mixtures
    • Authors: Liu Tan; Dabin Liu, Sen Xu, Qiujie Wu, Lianghong Xia
      Pages: 1315 - 1324
      Abstract: A study has examined the effect of mixing methods on the thermal stability and detonation characteristics of ammonium nitrate (AN) and sodium chloride (NaCl) mixtures. NaCl was mixed with AN by two methods. The thermal stability, detonation velocity and structural properties were investigated by differential scanning calorimetry (DSC), measurement of detonation velocity and X-ray diffraction (XRD). For the mechanical mixing method, in all tested scope of proportions of NaCl in the mixtures, activation energies increase when the proportion of NaCl increases; for solution mixing method, the activation energies decrease first and then start to increase as the proportion of NaCl increases. The detonation velocity of AN-NaCl mixtures prepared by two mixing methods also showed different results. The results indicate that the mixing methods significantly affect the thermal stability and detonation characteristics of AN.
      PubDate: 2017-09-08T01:21:11.641268-05:
      DOI: 10.1002/prep.201700108
       
  • Explosion Performance of High-Temperature Degraded Emulsion Explosives
    • Authors: Fei Wang; Honghao Ma, Zhaowu Shen
      Pages: 1325 - 1332
      Abstract: Experiments were conducted to study the underwater explosion performance of emulsion explosives (EE) after hot water bath. Spherical charges of EE with different sensitizers and hot water bath were prepared and tested. As for as-prepared charges, the detonation velocity experiments and underwater explosion experiments were carried out and the crystallization ratio was measured and calculated by the dissolution and neutralization method. The results showed an inverse relationship between explosion parameters (pressure peak, specific impulse, detonation velocity and specific total energy) and heating time. It also revealed that the effective explosive weight of EE was reduced with long time of hot water bath. Moreover, the crystallization ratio and the decreasing rate of explosion parameters of EE sensitized by NaNO2 were apparently higher than EE containing physical sensitizers (glass microballoon and perlite), which was attributed to the different destruction mechanism of EE. After 6-hour hot water bath, the EE containing physical sensitizers still retained detonator sensitivity and more than 80 % of specific total energy. Meanwhile, the crystallization ratio was less than 20 %. Whereas, the EE sensitized by NaNO2 lost the detonator sensitivity and the crystallization ratio of EE was also above 40 %.
      PubDate: 2017-09-11T10:05:11.40927-05:0
      DOI: 10.1002/prep.201700052
       
  • Forthcoming Meetings: Prop., Explos., Pyrotech. 11/2017
    • Pages: 1333 - 1334
      PubDate: 2017-11-23T09:12:52.936603-05:
      DOI: 10.1002/prep.201781198
       
  • Future Articles: Prop., Explos., Pyrotech. 12/2017
    • Pages: 1336 - 1336
      PubDate: 2017-11-23T09:12:53.859068-05:
      DOI: 10.1002/prep.201781199
       
  • Inside Back Cover: Effects of an Organic-inorganic Nanocomposite Additive
           on the Combustion and Erosion Performance of High Energy Propellants
           Containing RDX (Prop., Explos., Pyrotech. 11/2017)
    • Authors: Na Sun; Zhenggang Xiao
      Pages: 1337 - 1337
      Abstract: The inside backcover picture shows a novel microcapsule with an organic-inorganic nanocomposite shell which was designed and applied as a functional additive for modifying high energy propellants to reduce their erosion performance. As the addition of nanocomposites reached the maximum values of 5.1 %, the erosivity of modified propellant reduced by 37.0 %. The plausible anti-erosion mechanisms for this microcapsule could be: the microcapsule with high heat absorption property could produce a lower flame temperature, and the nanoparticles deriving from microcapsule surface can be deposited on the erosion tube surface and formed a thermal-protective coating. More details can be found in the Full Paper by N. Sun and Z. Xiao on page 1252 ff.
      PubDate: 2017-11-23T09:12:52.87996-05:0
      DOI: 10.1002/prep.201781103
       
  • Back Cover: Hot Spot Formation in Mock Materials in Impact Sensitivity
           Testing by Drop Hammer (Prop., Explos., Pyrotech. 11/2017)
    • Authors: John G. Reynolds; Peter C. Hsu, Gary A. Hust, Stephen A. Strout, H. Keo Springer
      Pages: 1338 - 1338
      Abstract: The back cover picture shows an artist depiction of the formation of hot spots in the drop hammer test. In this test, a sample on sandpaper is placed between two hardened anvil surfaces, shown on the right with a sample in between. A heavy weight is dropped on the top anvil, raised higher and higher until a reaction is noted, thought to be instigated by hot spot formation. In this case for sugar, a mock explosive, the formation of hot spots leads to discoloration only, depicted in the top left as bright yellow-orange spots. The central part of the figure shows the spent sample with sugar-sandpaper-hot spots after the drop weight and top anvil have been retracted. Artist: Jacob G. Long. More details are discussed in the article by John G. Reynolds et al. on page 1303 ff.
      PubDate: 2017-11-23T09:12:54.37891-05:0
      DOI: 10.1002/prep.201781104
       
 
 
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