Energetic Plasticizers Research Articles

ECR Spotlight – Matthew Gilbert

ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Matthew Gilbert is an author on ‘ Measuring maximum heart rate to study cardiac thermal performance and heat tolerance in fishes’, published in JEB. Matthew is an Assistant Professor of Animal Physiology at the Institute of Arctic Biology, University of Alaska Fairbanks, USA, investigating environmental drivers of cardiorespiratory and energetic plasticity, thermal physiology and exercise physiology.

Preparation and study of some characteristics of spherical gunpowder based on nitrocellulose and DINA

This article presents the results of research on the selection of components, recipes, method and technological regime for the production of spherical gunpowders based on nitrocellulose (grade Pi-BA) and ethylene glycol-N-nitramine dinitrate (DINA), as well as the results of studying some of their characteristics. In these gunpowders, DINA plays the role of an energetic plasticizer with a content in the range of 8.2 - 39.4% by mass. The selected technological regime allows to obtain spherical gunpowders with high yield on a laboratory scale (over 95% for particle sizes less than 1 mm and over 90% for particle sizes in the range of 0.2 - 0.8 mm). The obtained samples of spherical gunpowders have a density in the range of 1.60 - 1.62 g/cm3 and a bulk density in the range of 0.98 - 1.02 g/cm3, which well meets the requirements commonly applied to these criteria for military-use spherical gunpowders. The introduction of DINA has slight effect on the auto-ignition temperature of the obtained samples. Theoretical calculations of some energetic characteristics using the REALWIN program also show the potential of using DINA to replace nitroglycerin as a second energetic component in the development of high-energy spherical gunpowder.

Investigation of the Synthesis and Energetic Properties of an ANTA-Based Energetic Plasticizer.

Energetic plasticizers are being sought for their use in energetic formulations when combined with explosives. An energetic plasticizer based on the insensitive highly explosive 3-amino-5-nitro-l,2,4-triazole (ANTA) was synthesized and characterized by spectroscopy, X-ray crystallography, thermal analyses, and safety testing. Lastly, density functional theory calculations were employed to examine the observed selectivity among the three nucleophilic ring nitrogen atoms of ANTA toward electrophiles such as ANTA acrylate; this selectivity was found to be a combination of steric, electronic, and hydrogen bonding effects.

Thermal decomposition kinetics and storage life prediction of nitramine propellants with different energetic plasticizers based on model-fitting method

The research on the thermal decomposition of propellant is critical to determining its safe storage life. The thermogravimetry (TG) testing of nitramine propellants plasticized by nitroglycerin (NG), glycidyl azide polymer (GAP), 2,2-dinitropropanol hexanoate (DNPH), and N-butyl-2-nitratoethylnitramine (BuNENA) was performed under non-isothermal circumstances. The thermal decomposition mechanism of propellant was then analyzed using the model-fitting method, and the storage life was predicted based on the mechanism. The results show that when heated to the same mass loss, the temperature of GAP-NC-RDX, BuNENA-NC-RDX, and DNPH-NC-RDX is higher than that of NG-NC-RDX. GAP-NC-RDX, BuNENA-NC-RDX, and DNPH-NC-RDX propellants have superior thermal stability to that of NG-NC-RDX. The kinetic mechanism functions and equations of the propellants were calculated, and multi-step reaction models of the thermal decomposition were built. The major thermal decomposition mechanism of nitramine propellants was discovered to be composite autocatalytic decomposition (Kamal-Sourour equation), which means that the reaction of reactants and the reaction catalyzed by products occur in tandem. The decomposition depth of propellants increases as the temperature rises during the same storage time. The storage lifetimes of GAP-NC-RDX, BuNENA-NC-RDX, DNPH-NC-RDX, and NG-NC-RDX propellants at 288 K are 28.71 years, 24.49 years, 18.34 years, and 16.33 years, respectively. The inclusion of GAP, DNPH, and BuNENA in the formulation improves the storage life of propellant more than NG. This study offers an attractive strategy for analyzing the decomposition mechanism of propellant with a multi-step decomposition reaction and forecasting its storage life.

Aging mechanisms and kinetics of bis(2,2 dinitropropyl) formal facilitated by transition state bifurcation and HONO catalysis

Serving as energetic plasticizer, revealing the aging mechanisms and kinetics of bis(2,2-dinitropropyl) formal is helpful to remove the safety hazards. Here, based on the DFT barrier of methylene-H abstraction by nitro group (HONO elimination) and the continuous reaction model, an experimentally comparable half-life of BDNPF is reported by transition state theory simulation. Rather than the HONO elimination-addition reactions, HONO bimolecular decompositions are preferred, where the energetically preferred pathway involves formation of N2O3, and generation of N2O4 and HNO catalyzed by HONO. Interestingly, newly reported transition state bifurcations lower the barriers and accelerate HONO decomposition, which also leads to the rate constant of generating HNO consistent with experiments. Moreover, HNO undertakes hydrogen transferred bimolecular pathway and HONO-catalyzed pathway to decompose into N2O and H2O. This work clarifies the degradation pathways and species, and is helpful to the deep understanding of the aging procedures of energetic materials.

Nitramino-polymer with ether bridges and 1,2,3-triazole subunits incorporated into the polymer chain

The creation of novel energetic polymers for future advanced solid composite propellants and gunpowder is an urgent area of modern research. A simple and effective waste-free cycloaddition reaction between dialkyne and diazide comonomers, both bearing nitramine groups, for the synthesis of an energetic polymer containing explosophoric units in the polymer chain has been described. Neither solvent nor catalyst is required for the production of this polymer, the comonomers used are readily available, and the product does not need any purification, and, importantly, this protocol scales well. The resulting polymer, C1Z1, (C14H22N12O8)n, was comprehensively characterized by spectral and physico-chemical methods. Compatibility with energetic plasticizers (NG, DNDEG, DANPE), thermochemical characteristics and combustion features indicate the prospects of target polymer C1Z1 (density, ρ = 1.484 g/cm3; onset temperatures is 230 °C; positive enthalpy of the formation, ΔHf0 = +636 kJ/kg; burning rate at 10 MPa is 9.5 mm/s) as a binder base for energetic materials. Comparison of C1Z1 with nitrocellulose (NC) and their compositions with plasticizers revealed the advantages of C1Z1.

Metabolic engineering of Candida tropicalis for efficient 1,2,4-butanetriol production

1,2,4-Butanetriol serves as a precursor in the manufacture of diverse pharmaceuticals and the energetic plasticizer 1,2,4-butanetriol trinitrate. The study involved further modifications to an engineered Candida tropicalis strain, aimed at improving the production efficiency of 1,2,4-butanetriol. Faced with the issue of xylonate accumulation due to the low activity of heterologous xylonate dehydratase, we modulated iron metabolism at the transcriptional level to boost intracellular iron ion availability, thus enhancing the enzyme activity by 2.2-fold. Addressing the NADPH shortfall encountered during 1,2,4-butanetriol biosynthesis, we overexpressed pivotal genes in the NADPH regeneration pathway, achieving a 1,2,4-butanetriol yield of 3.2 g/L. The introduction of calcium carbonate to maintain pH balance led to an increased yield of 4 g/L, marking a 111% improvement over the baseline strain. Finally, the use of corncob hydrolysate as a substrate culminated in 1,2,4-butanetriol production of 3.42 g/L, thereby identifying a novel host for the conversion of corncob hydrolysate to 1,2,4-butanetriol.

Enhanced gas and plasticizer barrier HTPB composite liner implanted with parallel orientation Fe3O4/RGO nanosheets by an ultrasound/magnet-coassisted method

It is of great significance to prepare liners with excellent inhibition of energetic plasticizer migration and gas barrier properties. Here, we have successfully prepared magnetic iron oxide decorated reduced-graphene-oxide nanosheets (MRGO) by using ultrasound-assisted method. The obtained MRGO nanosheet-fillers were filled into hydroxyl-terminated polybutadiene (HTPB) which was exposed to a magnetic field (200 mT) to achieve ordered orientation of MRGO in the HTPB matrix (Ordered MRGO/HTPB). The laser confocal microscopy demonstrates that MRGO exhibit ordered orientation structure in HTPB matrix with good dispersion, which renders the HTPB composite liners exhibiting high gas and plasticizer barrier capability, with a reduction of 18.9 % in water vapor permeability and a decrease of 14.1 % in dibutyl phthalate (DBP) migration equilibrium concentration as compared with those of random MRGO embedded HTPB composite liners (Random MRGO/HTPB). Moreover, a theoretical model accounting for such enhanced gas/plasticizer barrier performance of HTPB due to the implantation of order aligned MRGO was established, which shows that the effective diffusion pathways of plasticizer/gas for liner penetration would be significantly enhanced when the MRGO nanosheets are oriented within the HTPB matrix. This work provides an effective and facile strategy toward the design and development of composite liners with high plasticizer/gas barrier performance for industrial applications.

Ballistic and thermal characterisation of greener composite solid propellants based on phase stabilized ammonium nitrate

Several representatives of a new class of "greener" propellants, comprising polyurethanes (based on recycled PET) as the binder, phase stabilized ammonium nitrate (PSAN) as the eco-friendly oxidizer, and triethylene glycol dinitrate (TEGDN) as the energetic plasticizer, together with aluminium-magnesium alloy as fuel and iron oxide powder (α-Fe2O3) as the catalyst, were prepared and investigated through specific analytical tools. Besides morphological and compositional investigations, the thermal behaviour and ballistic properties of the propellants were determined, and compared to those of consecrated propellants compositions, based on ammonium perchlorate. The calorimetric tests were used to measure the heat of combustion and specific volume. Impact and friction sensitivities were also measured. The ballistic tests carried out in closed bomb and the original data processing approach used allowed, in addition to the propellant force and covolume, the identification of a critical parameter such as the power index from Vieille's law of the burning rate.

UV-VUV absorption spectra of azido-based energetic plasticizer bis(1,3-diazido prop-2-yl)malonate in gas phase.

Ultraviolet and vacuum ultraviolet photo-absorption spectra of azido (-N3)-based energetic plasticizer, bis(1,3-diazido-prop-2-yl)-malonate (abbreviated as BDAzPM), in the gas phase is recorded at room temperature and in the photon energy range of 5.5-9.9eV using a synchrotron radiation source. Complementary computational results obtained using the time-dependent density functional theory document the vertical transition energies and oscillator strengths. Comparison of the simulated spectra with the experimental absorption spectrum of BDAzPM reveals that the early part of the absorption spectrum of BDAzPM is of pure valence excitation character, whereas the later intense part of the absorption spectrum is dominated by mixed Rydberg and valence electronic excitations.

Azidomethyl-bisoxadiazol-linked-1,2,3-triazole-(ABT)-based potential liquid propellant and energetic plasticizer.

A scalable synthesis of azidomethyl bisoxadiazol linked-1,2,3-triazole-(ABT) based potential liquid propellant and energetic plasticizer is obtained from commercially available diaminomaleonitrile in excellent yield. Newly synthesized compounds were fully characterized by various spectroscopic techniques. These materials exhibit good densities (1.77 g cm-3) and high thermal stabilities (Td = 181 °C). Compound 5 has good detonation properties (5, P = 20.81 GPa, D = 7516 ms-1) and propulsive properties (Isp (neat) = 210 s). These are superior to TNT and GAP and comparable to BAMOD, making them potential green liquid rocket propellants and energetic plasticizers.

Performance characteristics of nitramine‐based gun propellants with TEGDN as energetic plasticizer

AbstractThis study mainly explored the performance characteristics of nitramine‐based (NB) gun propellants using TEGDN as an energetic plasticizer by experimental method. Three series of NB gun propellant samples with RDX, HMX or CL‐20 were prepared referring to the formulation of JA2 gun propellant. Their thermochemical characteristics, explosion heat, chemical stability and compatibility, impact, friction and electrostatic spark sensitivities, and compressive strength were determined by various instruments. The experimental results indicated that the NB gun propellant samples with RDX have lower decomposition temperature, and those with CL‐20 have higher thermogravimetric loss. Three series of NB gun propellant samples have good chemical stability and compatibility, and their explosion heat is close to that of JA2 gun propellant, but their sensitivity is lower than that of JA2 gun propellant. The maximum stress of three series of NB gun propellant samples decreases with increasing cyclic nitramine (RDX, HMX or CL‐20) content, and their compressive strength is better than that of JA2 gun propellant.

Influence of different energetic plasticizers on the performance of NC-RDX nitramine gun propellants

Energetic plasticizers are an essential component of propellants and have a significant impact on their performance, such as energy, combustion, and mechanics. Therefore, there is significant practical value in understanding how plasticizers affect the performance of propellants. In this work, the glass transition temperatures of several energetic plasticizers were compared. By adding energetic plasticizers with good compatibility with the propellant and a low glass transition temperature to the propellant, nitramine gun propellants containing different energetic plasticizers were prepared through a semi-solvent method. The compatibility, thermal behavior, phase structure, composition, mechanical properties, energy, and combustion performance of the nitramine gun propellants were characterized. The influence of plasticizers on the phase structure of the propellant and its mechanism on the combustion performance of the propellant were discussed. Energetic plasticizers GAPE, DNPH, and BuNENA have good compatibility and chemical stability with NC-RDX and display good plasticization. GAPE–NC–RDX, DNPH–NC–RDX, and BuNENA–NC–RDX propellants exhibit stable combustion performance at −40 °C, 20 °C, and 50 °C. Compared with the nitramine gun propellant plasticized with NG, the impact strength of the propellant plasticized with DNPH and BuNENA increased by 108.1 % and 17.2 % at −40 °C, respectively. This work offers a solution to improve the phase structure, mechanical properties, and combustion stability of heterogeneous gun propellants and provides a way to suppress the excessive burning rate and flame temperature of propellants.

Preparation and Properties of a Novel High-Toughness Solid Propellant Adhesive System Based on Glycidyl Azide Polymer-Energetic Thermoplastic Elastomer/Nitrocellulose/Butyl Nitrate Ethyl Nitramine.

Glycidyl azide polymer (GAP)-energetic thermoplastic elastomer (GAP-ETPE) propellants have high development prospects as green solid propellants, but the preparation of GAP-ETPEs with excellent performance is still a challenge. Improving the performance of the adhesive system in a propellant by introducing a plasticizer is an effective approach to increasing the energy and toughness of the propellant. Herein, a novel high-strength solid propellant adhesive system was proposed with GAP-ETPEs as the adhesive skeleton, butyl nitrate ethyl nitramine (Bu-NENA) as the energetic plasticizer, and nitrocellulose (NC) as the reinforcing agent. The effects of the structural factors on its properties were studied. The results showed that the binder system would give the propellant better mechanical and safety properties. The results can provide a reference for the structure design, forming process, and parameter selection of high-performance GAP-based green solid propellants.

Development of a Gas Chromatography with High-Resolution Time-of-Flight Mass Spectrometry Methodology for BDNPA/F.

Analysis of thermally labile compounds such as bis(2,2-dinitropropyl) acetal/formal (BDNPA/F), an energetic plasticizer, is usually performed via liquid chromatography (LC) as opposed to gas chromatography (GC) due to thermal decomposition in the inlet or the analytical column. While LC is a powerful technique, the analysis of volatile and semivolatile compounds is best suited to GC. Herein, a method was developed for a gas chromatograph coupled to high-resolution mass spectrometer (GC-HRMS), utilizing a programmable temperature vaporizer (PTV) inlet. A subset of the native compounds and several produced by the thermal decomposition of BDNPA/F in the inlet were evaluated by using multiple PTV inlet parameters to determine the optimal ramp rate and final temperature of the inlet (60 °C/min from 60 to 325 °C). The optimized GC-HRMS method nearly reduced all thermal decomposition, allowing for an excellent separation to be obtained. Furthermore, multiple ionization methods, including electron impact (EI), negative chemical ionization (NCI), and positive chemical ionization (PCI), were used to explore the many chemical differences between the BDNPA/F samples. A preliminary investigation of the benefits of using GC-HRMS to evaluate the chemical differences between unaged and aged BDNPA/F samples for unique insight was evaluated.

Energetic Polymer Possessing Furazan, 1,2,3-Triazole, and Nitramine Subunits.

A [3 + 2] cycloaddition reaction using dialkyne and diazide comonomers, both bearing explosophoric groups, to synthesize energetic polymers containing furazan and 1,2,3-triazole ring as well as nitramine group in the polymer chain have been described. The developed solvent- and catalyst-free approach is methodologically simple and effective, the comonomers used are easily available, and the resulting polymer does not need any purification. All this makes it a promising tool for the synthesis of energetic polymers. The protocol was utilized to generate multigram quantities of the target polymer, which has been comprehensively investigated. The resulting polymer was fully characterized by spectral and physico-chemical methods. Compatibility with energetic plasticizers, thermochemical characteristics, and combustion features indicate the prospects of this polymer as a binder base for energetic materials. The polymer of this study surpasses the benchmark energetic polymer, nitrocellulose (NC), in a number of properties.

Synthesis of nitroxyethylnitramine (NENA) plasticizers and dinitroxydiethylnitramine (DINA) in continuous flow**

AbstractNitroxyethylnitramines (NENAs) and dinitroxydiethylnitramine (DINA) are useful energetic plasticizer components in propellants and explosives. However, their synthesis at large scale can be delicate because it involves two dissimilar nitration reactions: nitrate ester formation and halide‐catalyzed nitramine formation. Consequently, these preparations, and particularly when conducted in a single‐stage/pot operation, are problematic with respect to issues such as process safety (heat transfer, temperature control), product purity, replicability and operability. Herein, we briefly review procedures for preparation of NENAs and/or DINA and then report on our own work on continuous flow synthesis of this family of nitramine‐nitrate ester compounds. We find them to be particularly suited for flow synthesis. Our studies are first and foremost distinguished from previous ones by focusing on the use of acetyl chloride as a metal‐free, convenient chloride catalyst and the application of glacial acetic acid as a salt‐forming secondary amine solvent, thus facilitating pumping of the amino alcohols and preventing local exotherms. We have also incorporated post‐reaction simmering of the final flow effluent to enhance product purities by removal of nitroso impurities.

Synaptic modifications transform neural networks to function without oxygen

BackgroundNeural circuit function is highly sensitive to energetic limitations. Much like mammals, brain activity in American bullfrogs quickly fails in hypoxia. However, after emergence from overwintering, circuits transform to function for approximately 30-fold longer without oxygen using only anaerobic glycolysis for fuel, a unique trait among vertebrates considering the high cost of network activity. Here, we assessed neuronal functions that normally limit network output and identified components that undergo energetic plasticity to increase robustness in hypoxia.ResultsIn control animals, oxygen deprivation depressed excitatory synaptic drive within native circuits, which decreased postsynaptic firing to cause network failure within minutes. Assessments of evoked and spontaneous synaptic transmission showed that hypoxia impairs synaptic communication at pre- and postsynaptic loci. However, control neurons maintained membrane potentials and a capacity for firing during hypoxia, indicating that those processes do not limit network activity. After overwintering, synaptic transmission persisted in hypoxia to sustain motor function for at least 2 h.ConclusionsAlterations that allow anaerobic metabolism to fuel synapses are critical for transforming a circuit to function without oxygen. Data from many vertebrate species indicate that anaerobic glycolysis cannot fuel active synapses due to the low ATP yield of this pathway. Thus, our results point to a unique strategy whereby synapses switch from oxidative to exclusively anaerobic glycolytic metabolism to preserve circuit function during prolonged energy limitations.

EPDM insulation modified with vinyl triethoxysilane functionalized GO to prevent plasticizer migration in solid propellant

Excessive plasticizer migration to the insulation will have a serious impact on the safety of solid propellants. In this paper, the anti-migration EPDM insulation was prepared by introducing vinyl triethoxysilane functionalized GO (GS) as modifiers to prevent the migration of energetic plasticizers. The anti-migration performance at different temperatures was evaluated by immersion tests. The concentration of mixed plasticizers that migrated into the EPDM/GS-3 at 30 °C was decreased from 24.7% to 20.4% (17.4% decrease). The results confirmed that the introduction of GS prevented the migration of plasticizers to the EPDM insulation. The SEM results showed that GS was well-dispersed in the insulation, and there is strong interfacial interaction between GS and EPDM chains. Our research provided a new method to prepare EPDM insulation with excellent anti-migration performance.

Understanding the alkyl effect of geminal dinitropropyl ester energetic plasticizers on hydroxyl terminated polybutadiene (HTPB): Simultaneous tuning on low temperature behavior and processability

Geminal dinitropropyl ester plasticizers (DNPEPs) possess excellent energetic performances which provide good potentials as insensitive plasticizer. In this study, we design and synthesize DNPEPs with different alkane chain parts, and systematically investigate their structure-property relationships. Results show that DNPEPs have impact sensitivities all higher than 25.2 J, thermal decomposition temperatures all higher than 254 °C, and glass transition temperatures ( T g ) lower than −90 °C. Furthermore, the effects of DNPEPs as plasticizer are studied on hydroxyl terminated polybutadiene (HTPB) in detail, including the viscosity, glass transition temperatures and others. It is noteworthy that 2,2-dinitropropyl nonanoate (DNPNc) among these DNPEPs exhibits the most expected simultaneous tuning effects on both viscosity and T g of HTPB systems, providing favorable potentials to replace the conventional plastizers as dioctyl sebacate (DOS) in the HTPB based propellants and explosives.