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Fullerene Stabilizer 4,11,15,30-Tetraarylamino Fullerenoarylaziridine: Regioselective Synthesis, Crystallographic Characterization Derivatives, and Potential Application as Propellant Stabilizer
Abstract
The safe storage of propellants has become increasingly challenging due to extreme storage and operational environments. Hence, high-performance stabilizers should be urgently developed to improve the stability of propellants. In consideration of the stability mechanism of stabilizers and the excellent free radical scavenging ability of fullerenes, six fullerene stabilizers, 4,11,15,30-tetraarylamino fullerenoarylaziridines, were synthesized through the nucleophilic substitution reaction of hexachlorofullerene (C60Cl6) and corresponding aromatic amines with high yields. Their structures were adequately confirmed by HRMS, FT-IR, UV-Vis, 1H NMR, 13C NMR spectroscopy and single-crystal X-ray diffraction. The results of methyl violet test paper and thermogravimetric analysis manifested that the stabilities of these multifunctional fullerene derivatives to nitrocellulose were remarkably better than traditional stabilizers, such as N, N’-dimethyl-N, N’-diphenylurea and diphenylamine. Further electron paramagnetic resonance spectroscopy and FT-IR analysis reasonably revealed that this excellent stability ascribed the efficient scavenging ability for nitroxide radicals produced by nitrocellulose pyrolysis, thereby inhibiting the autocatalytic decomposition of nitrocellulose.
... Double base propellants (DBPs) are widely used for solid rocket motors and missile weapons owing to their high energy, wide range of burn rates, and low gas emissions [1]. DBPs are mainly composed of nitrate esters compounds [2]. ...
... Consequently, significant challenges have prompted the scientific community to seek effective alternatives. In this context, some other organic and inorganic chemical substances, such as fullerene-derivatives [1], phenols [11], lignin [12], triphenylamine (TPA), polymers, ketones, N-methylp-nitroaniline derivatives, ionic liquids [13], natural products [14], zeolites [15], and malonanilides [16], have been tested as stabilizers for nitrate esters. Nevertheless, it is found that the replacement of the classical stabilizers with new compounds presenting less/ no effect on the environment and human health is at the expense of the energetic material stability. ...
This study explored the stability and thermo-kinetic features of double base nitrocellulose (NC)/diethylene glycol dinitrate (DEGDN) propellant supplemented with Kraft lignin. For this purpose, the impact of 2-nitrodiphenyl-amine (2-NDPA), 1,3-dimethyl-1,3-diphenylurea (C-II) and lignin stabilizers on the molecular structure, morphology, and thermokinetic behavior of NC/ DEGDN composite were thoroughly analyzed. Experimental results showed that lignin exhibits promising stabilizing efficiency comparable to that of the conventional 2-NDPA and C-II. In addition, thermal findings highlighted that the incorporation of 2-NDPA, C-II, and lignin has improved the thermal decomposition temperature of NC/DEGDN propellant. The investigation of the thermolysis kinetics of stabilized NC/DEGDN composites demonstrated an increase in the Arrhenius parameters with respect to the NC/DEGDN base-line. Above all, this investigation contributes to the ongoing efforts to develop new environmentally friendly stabilizers for nitrate esters-based composites.
... Therefore, enhancing the chemical stability of such energetic materials remains one of the major challenges faced by researchers [26], and some new stabilizers, such as phenols, natural products, zeolite, ionic liquids and biopolymers, have been successively studied [27][28]. In recent years, fullerene-based stabilizers have been considered potential substitutes for traditional stabilizers because of their excellent nitrogen oxide radical scavenging ability [29][30][31][32][33]. ...
A series of aryl[70]fulleropyrrolidine (5a–5b’) were successfully designed and synthesized using Prato reaction. The results of non-isothermal thermal analysis showed that 5a–5b’ can increase the critical explosion temperature of nitrocellulose by 0.8–1.8 K. The results of isothermal experiments proved that 5a–5b’ can prolong the discoloration time of methyl violet test paper of nitrocellulose at 407.65 K and the safe storage life of nitrocellulose at 323.15 K by 87 min and 34.46 years, respectively. The adiabatic accelerated calorimetry analysis showed that 5a–5b’ can reduce the initial autocatalytic decomposition reaction of nitrocellulose. The thermal stability of 5a–5b’ to nitrocellulose was proved to mainly depends on the nitrogen oxide radical scavenging ability of fullerene. Obviously, a small amount of aryl[70]fulleropyrrolidine mixed with aryl[60]fulleropyrrolidine can significantly improve the inhibition of aryl[60]fulleropyrrolidine on the thermal decomposition of nitrocellulose. Subsequently, the feasibility of low-cost and large-scale preparation of arylfulleropyrrolidine stabilizer using fullerene soot as precursor was explored.
... 2010年, Lin等 [13] 通过DSC方法研究了二苯胺含量对硝 化棉热分解过程的影响; 胡荣祖等 [14] 通过公式推导获 得了用非等温DSC数据估算硝化棉B na 自催化分解反 应热爆炸临界温升速率的表达式; Ma等 [15] 利用DSC与 TG-FTIR技术探究了硝化棉复合含能材料的热分解机 Table 2 The composition of nitrocellulose samples 534、1094 cm −1 为C 60 的特征吸收峰 [16] . 表征结果和化 合物2a~2d的官能团一致. ...
... The isothermal thermogravimetric analysis has been used to judge the stability of energetic materials, where a lower mass loss corresponds to a better stability (Z. Chai et al. 2020). Therefore, the studied systems were heated at a constant temperature of 140°C for 150 min, and the obtained results are exhibited in 325 Figure 11. ...
Nitrogen oxides NOx, which result from the decomposition of nitrocellulose (NC)-based solid propellants, promote the degradation of this latter and alter its long-term stability. Thus, to avoid such situation and ensure a better stability, conventional stabilizers such as aromatic amines or urea compounds are usually added to the NC-based formulations. However, these latter may generate carcinogenic and toxic species that may negatively affect both human health and environment. Herein, based on its selective adsorption capacity of NOx, the stability potential of a porous inorganic compound, namely, mordenite (MOR), on nitrocellulose was assessed. Three NC-based samples (S1-S3) were prepared through the incorporation of 3 wt.% of stabilizing agents, i.e., S1: pure NC, S2: NC+DPA and S3: NC+MOR. The effect on the stability of this inorganic compound with regard to pure NC has been highlighted utilizing stability tests and kinetic modeling. Beforehand, the compatibility of mordenite with nitrocellulose was initially checked by means of DSC and FTIR. Furthermore, the obtained results via Vacuum Stability Test (VST) and Bergmann-Junk (B&J) demonstrated that S3 displayed a better stability than S1 and comparable behavior to S2. The determination of the kinetic triplet by isoconversional methods confirmed the effectiveness of MOR as a stabilizing agent. These findings claim that such inorganic compound may be used efficiently as a stabilizer for NC-based energetic formulations.
This project performed quantum chemical computation, through kinetic and thermodynamic analyses to compare relative reactivity, reaction rate, and equilibrium composition from the possible pathways in connection with stabilizer-nitrodioxide reactions to determine the stability of the materials for practical application. Corresponding achievements have promoted the use of N-methyl-p-nitroaniline (MNA) and dinitrophenyl malonamide series (M3, M4, and M5) stabilizers as high priorities for selection.
The Gaussian 09 program (G09) (Frisch et al 2009) and density functional theory (DFT) calculations with the B3LYP/6-31G(d,p) function were performed to obtain related geometric and thermodynamic energy data for the molecular systems in this study. The synchronous transit-guided quasi-Newton method (STQN) (Peng and Schlegel Isr J Chem 33:49, 1993) was applied through the QST3 procedure to identify single imaginary frequency-valued transition-state species. The related reaction rate constant (k) and pre-exponential factor (A) were obtained, based on transition state theory (Su 2008), using Eqs. 11 and 12.
A series of aziridino[60]fullerenes was synthesized by the reaction of octabromo[60]fullerene with various anilines. Their ability to absorb free radicals and acid gases was studied, and their potential applications as stabilizers in nitrocellulose-containing propellants were discussed. The results of differential thermal analysis showed that aziridino[60]fullerene can increase the exothermic peak temperatures of nitrocellulose by 0.55–2.37 °C. The methyl violet test found that aziridino[60]fullerenes can extend the complete decomposition period by 31–71 min. The results of vacuum stability test and thermogravimetric test indicated that aziridino[60]fullerene can delay the decomposition of nitrocellulose. Furthermore, their stabilization mechanism was studied by electron spin resonance spectroscopy, and the free-radical scavenging rate of 3c reached 86.09%. The findings demonstrate that aziridino[60]fullerenes could effectively eliminate the nitrogen oxides released by nitrocellulose autocatalysis and might be used as a new stabilizer for nitrocellulose-containing propellants.
Graphical abstract
Carbon material is an important additive in energetic materials. Graphene is a monolayer carbon material in which carbon atoms are arranged in two-dimensional honeycomb structure, who has special optical, electrical, and mechanical properties. Recently, the application of graphene-based composites in energetic materials has received extensive attention. This review mainly summarizes the applications of graphene and graphene-based nanomaterials in energetic materials. The effects of these materials on the thermal stability, sensitivity, mechanical property, ignition and combustion of energetic materials were discussed. Furthermore, the progress of functionalized modification of graphene has been summarized, including covalent bonding modification and doping modification. These studies show that graphene-based materials exhibit excellent performances and might emerge as promising candidate for energetic materials.
A novel natural macromolecule stabilizer, tea polyphenol, was developed based on the scavenging effect of nitroxide radical to enhance the thermal stability of nitrocellulose. The structural of tea polyphenols was confirmed by infrared spectroscopy, and their good thermal stability of tea polyphenols in nitrocellulose was confirmed by methyl violet paper test and vacuum stability test. The iso-thermogravimetric test showed that tea polyphenols could prolong the safe storage life of nitrocellulose. The inhibition of tea polyphenols on the autocatalytic thermal decomposition of nitrocellulose in the early stage of nitrocellulose thermal decomposition was confirmed by SEM images at different stages of nitrocellulose thermal decomposition. The thermal interaction between tea polyphenols and nitrocellulose was further analyzed by non-isothermal thermal analysis. Experiments confirmed that tea polyphenols can enhance the thermal stability of nitrocellulose. Their addition increased the T0 of nitrocellulose by 2.0–9.4 ℃, the Tbp0 by 1.4–9.6 ℃, and the activation energy of nitrocellulose by 5.38–9.77 kJ·mol–1.
Fullerene derivatives are considered as potential stabilizers for nitrocellulose-based propellants due to their efficient radical scavenging ability. However, most of the studies were focus on [60]fullerene derivatives, while the more electron-absorbing [70]fullerene derivatives are rarely studied. Accordingly, a series of arylamino[70]fullerenoarylaziridine (2a–g) was successfully designed and synthesized. The thermal stability of 2a–g on nitrocellulose was investigated using the methyl violet test and isotemperature TG test. The results indicated that 2a–g have excellent thermal stability on nitrocellulose, and it can prolong the safe storage life of nitrocellulose, which is superior to that of traditional stabilizer (diphenylamine) and [60]fullerene-based stabilizers. Further thermal analysis revealed the thermal behavior of 2a–g in the states of adiabatic, isothermal, and non-isothermal decomposition of nitrocellulose. The addition of 2a–g increased the critical temperature of the thermal explosion of nitrocellulose by 5.6–7.5 °C and the activation energy of nitrocellulose by 7.52–30.03 kJ mol–1. In addition, 2a–g can reduce the influence of thermal decomposition products on nitrocellulose and improve the initial decomposition temperature. The thermal stability of 2a–g with different substituents to nitrocellulose was compared, and basic-involved thermal interaction between 2a–g and nitrocellulose was further investigated. The results showed that the thermal stability of nitrocellulose by fullerene-based stabilizers is affected by two factors: alkalinity difference caused by substituents on the aniline groups and radical scavenging ability difference caused by fullerenes.
The thermal decomposition or even explosion of nitrocellulose during long-term storage is prevented by adding stabilizers to nitrocellulose-based propellants. A series of novel arylmalonamide[70]fullerocyclopropane (3a–c) were synthesized through Bingel reaction. The molecular structures of 3a–c were verified through ¹H NMR, ¹³C NMR, Fourier transform infrared spectroscopy (FT-IR), UV–visible spectroscopy, and mass spectrum. The thermal stability of 3a–c to nitrocellulose was studied by methyl violet paper test and iso-thermogravimetry method, and the results showed that the stability of 3a–c to nitrocellulose was significantly better than that of the [60]fullerene-based stabilizers. The thermal stability of 3a–c to nitrocellulose improved as the increase of the carbon chain length on the p-position of the benzene ring. The effects of 3a–c on the thermal decomposition of nitrocellulose were obtained by differential thermal analysis, and the results showed that the critical temperature of the thermal explosion of nitrocellulose can be increased by 0.1–2.8 °C by 3a–c. The thermal stability of 3a–c to nitrocellulose in adiabatic environment was confirmed by accelerating rate calorimetry. In addition, the stabilization mechanism was studied through ESR and FT-IR, and the results showed that 3a–c can react with nitrogen oxide radicals released by nitrocellulose. These arylmalonamide[70]fullerocyclopropane with excellent thermal stability and strong radical scavenging ability can be used as a promising stabilizer for single and double based propellants.
A series of fullerene anisole derivative stabilizers was synthesized by nucleophilic substitution reaction using hexachlorofullerene and benzyl alcohol as raw materials to extend the service duration of nitrocellulose (NC)-based propellants. Single-crystal X-ray diffraction, nuclear magnetic resonance, high-resolution mass spectrometry, Fourier transform infrared (FT-IR) spectroscopy, and UV–Vis spectroscopy were used to characterize the structures of the synthesized fullerene anisole derivative stabilizers. Methyl violet, differential scanning calorimetry test, isothermal weight loss, vacuum stability test, and adiabatic accelerated test were used to study their compatibility with NC and their ability to stabilize NC. The results show that the designed and synthesized novel fullerene anisole derivative stabilizer has good compatibility with NC, and their overall stabilizing effects on NC are better than those of the traditional stabilizers, diphenylamine (DPA), and N,N′-dimethyl-N,N′-diphenylurea (C2). The stabilizing effects was ranked as: 3b > 2d > 2a > 2c > C2 > 2b > DPA > NC. In addition, FT-IR analysis and electron spin resonance spectroscopy were applied to explore the stability mechanism of fullerene-based stabilizers to NC. The results reveal that the new fullerene stabilizer can adsorb and effectively eliminate the nitrogen oxide free radicals generated by NC degradation; therefore, it can forbid the autocatalytic degradation of NC and stabilize NC.
To explore the effect of different positions and number of pyrrolidine bound to the carbon cage on the stabilization effect of fulleropyrrolidine derivatives to nitrocellulose (NC)/nitroglycerine (NG), we synthesized N-(4-methoxy) phenylpyrrolidine-C60 and four different of bis(N-(4-methoxy) phenylpyrrolidine)-C60 compounds through Prato reaction. Their structures were characterized by UV-vis, ¹H NMR, ¹³C NMR, high-resolution mass spectroscopy, and single-crystal X-ray diffraction. Their stabilization effect to NC/NG were investigated using differential scanning calorimetry, methyl violet, vacuum stabilization effect, weight loss, and accelerating rate calorimeter tests. The results indicated these compounds had excellent stabilization effect to NC/NG. The stabilization effect of the fulleropyrrolidine bisadducts to NC/NG is significantly better than that of fulleropyrrolidine monoadduct and C60. Moreover, the position where pyrrolidine binds to fullerene in fulleropyrrolidine bisadducts is different, and its stabilization effect to NC is also different. The stabilization effect order of different bisadduct isomers to nitrocellulose is as follows: e-edge> trans-2> cis-2> trans-3. Electron paramagnetic resonance (EPR) and FT-IR were used to study the stabilization mechanism of fulleropyrrolidine derivatives to NC/NG. The EPR results also show that fulleropyrrolidine bisadducts with different addition sites have different abilities to absorb nitroxide, and their ability is better than that of the monoadduct and C60, which is consistent with the results of stabilization effect performance test.
Characterization of materials at the nanoscale plays a crucial role in in-depth understanding the nature and processes of the substances. Mass spectrometry (MS) has characterization capabilities for nanomaterials (NMs) and nanostructures by offering reliable multi-dimensional information consisting of accurate mass, isotopic, and molecular structural information. In the last decade, MS has emerged as a powerful nano-characterization technique. This review comprehensively summarizes the capabilities of MS in various aspects of nano-characterization that greatly enrich the toolbox of nano research. Compared with other characterization techniques, MS has unique capabilities for real-time monitoring and tracking reaction intermediates and by-products. Moreover, MS has shown application potential in some novel aspects, such as MS imaging of the biodistribution and fate of NMs in animals and humans, stable isotopic tracing of NMs, and risk assessment of NMs, which deserve update and integration into the current knowledge framework of nano-characterization.
The effect of novel aniline-fullerene stabilizers on the decomposition of nitrocellulose (NC) was investigated using an isothermal analysis. In comparison with the activation energy of NC (144.7 kJ mol⁻¹), the activation energy of S-1, S-2, and S-3 at the early stage increased to 152.8, 158.6, and 159.0 kJ mol⁻¹, respectively. Remarkably, the effective storage times for the decomposition extent of S-1, S-2, and S-3 to reach a decomposition extent of 0.1% were 12.0, 30.5, and 20.9 years, respectively, which were longer than that of NC (10.6 years). In addition, the intermediate product produced by aniline-fullerene stabilizers and NC action was characterized, and the mechanism and interaction between the stabilizers and NC was revealed. The introduction of aniline-fullerene stabilizers can effectively obstruct further catalysis and accelerate the decomposition of NC by absorbing nitroxide free radical from the decomposition of NC. The results presented herein provide new insights into the stability and rational design of highly effective stabilizers.
The influence of N-methyl-4-nitroaniline (MNA) on the thermal stability of nitrocellulose (NC) was investigated via an isothermal decomposition dynamics research method. The Arrhenius equation and model-fitting were used to calculate the thermal decomposition kinetic parameters of NC and MNA/NC (3 wt%) composite. Results showed that the thermal decomposition activation energy of NC/MNA (3 wt%) was significantly increased compared with that of pure NC, indicating that the thermal stability of NC was increased with stabilizer MNA addition. Subsequently, the storage life of NC and MNA/NC (3 wt%) composite was estimated using Berthelot equation. It was found that if the decomposition extent reaches 0.1% as the end of life criterion, 3 wt% stabilizer MNA addition significantly extended the storage life of NC from 10.57 to 24.9 years at ambient temperature (298.15 K) with the life extension rate reaching 135.6%. Furthermore, the intermediate product produced by MNA and NC action was extracted and characterized via UV–Vis, HPLC, ¹H NMR, FT-IR, and LC–MS, and a possible stabilization mechanism of MNA to NC was proposed.
In this work, Fourier transform infrared spectroscopy (FTIR) and X‐ray powder diffraction (XRD) were selected as reliable, fast, and nondestructive techniques to assess their potentialities for characterization and discrimination of nitrocellulose (NC)‐based formulations containing different kinds of stabilizers and subjected to accelerated aging. Preliminary results based on visual comparison of the spectra point out that spectra obtained by both spectroscopic techniques were useful for a rapid detection of the aging process without additional sample preparation. Additionally, the existence of compatibility issues between NC and one of the stabilizers is easily recognized. The spectral data were subjected to principal component analysis (PCA) for visualization and to reveal differences between samples. The obtained results demonstrated that PCA plots were able to distinguish and classify the NC samples with respect to their respective stabilizers and aging.
Nitrate esters-based propellant (NEBP) belongs to the main classes of energetic materials being used in civilian and military applications. These NEBPs are not highly stable, and during aging, some of their functional characteristics may change, what can lead to serious safety problems. A thorough analytical characterization of NEBP is of fundamental importance to provide an adequate support for their stability and safe life assessment. Moreover, in order to safely store and fully exploit these energetic materials, accurate analytical techniques and strategies are indispensable to efficiently judge their properties during aging. Although various methodologies have been developed worldwide to evaluate the aging behavior of NEBP, the characterization is not a simple task and often involves the combination of several techniques, whose results have to be evaluated together. This review sought to evaluate existing analytical techniques which can be utilized for a suitable analysis of NEBP stability and aging, evidencing their respective advantages and shortcomings. The employment of each examined technique is described and discussed by relevant examples from the literature.
Aliphatic nitrate esters are currently the most widely used energetic ingredients in single-, double-, and triple-base propellants. These nitrate esters are unstable at ambient conditions and stabilizing agents should be incorporated into the energetic compositions to inhibit and slow down the decomposition reactions that can occur. However, the currently used stabilizers present a number of environmental and human health issues. To overcome these shortcomings, many stabilizers have been appeared in the past few decades and continue to be developed. Furthermore, several analytical techniques have been introduced to monitor the stability of nitrate ester-based energetic materials as well, since the existing ones could not be efficiently applied. Therefore, this review paper discusses and summarizes the current and emergent stabilizers as well as their mechanisms of action. A critical and analytical examination of their advantages and drawbacks is made.
In recent years, research in the field of carbon nanomaterials (CNMs), such as fullerenes, expanded graphite (EG), carbon nanotubes (CNTs), graphene, and graphene oxide (GO), have been widely used in energy storages, electronics, catalysts, biomaterials, as well as medical applications. Regarding energetic storage, one of the most important research directions is the development of CNMs as carriers of energetic components by coating or encapsulation, thus forming safer advanced nanostructures with better performances. Meanwhile, some of the CNMs can also be functionalized to become energetic additives. This review article covers updated preparation methods for the aforementioned CNMs, with a more specific orientation towards the use of these nanomaterials in energetic compositions. Besides, the effects of these functionalized CNMs on thermal decomposition, ignition, combustion and reactivity properties of energetic compositions are significant, which are further discussed with more details. It has been shown that the use of functionalized CNMs in energetic compositions would greatly improve their combustion performances, thermal stability and sensitivity. In particular, the functionalized Fullerene, CNTs and GO are the most appropriate candidate components in nanothermites, solid propellants and gas generators, due to their superior catalytic properties as well as facile preparation methods.
A comparative study of the thermal decomposition of naturally and artificially aged double-base propellants has been carried out at five different heating rates in a dynamic nitrogen atmosphere using differential scanning calorimetry (DSC) technique. The results show that there is only one decomposition peak on DSC curves, and this decomposition has been accelerated by ageing. The influence of the heating rate on the DSC behaviour of the propellants was verified. The kinetic parameters such as activation energy and frequency factor and the thermodynamic parameters such as the enthalpy of activation, free energy of activation and critical explosion temperature for the compounds were obtained from DSC data using non-isothermal methods proposed by Kissinger and Ozawa. On the other hand, a prediction of the in-service period by van't Hoff's equation was performed and compared with the experimental results in order to check the constancy and validity of this method. As a result, the prediction procedure used to obtain the time–temperature profile was achieved with good accordance. Copyright © 2012 John Wiley & Sons, Ltd.
Tremendous progress has been made on the design and processing of new active and interfacial materials to enable organic photovoltaics to achieve high power conversion efficiencies of >10%. In this Feature Article the development of functional fullerenes as (1) acceptors, (2) electron selective layers, and (3) morphology stabilizers for bulk heterojunction polymer solar cells is reviewed. In addition to the standard PCBM based acceptors, a wide variety of newly developed fullerene-derived molecules have appeared in the past few years and started to show very encouraging photovoltaic performance when they were blended with low bandgap conjugated polymers. New fullerene derivatives with proper molecular design can also serve as electron selective interfacial materials and morphology stabilizers for the bulk heterojunction layer, which are essential to improve the interfacial property and long term stability of polymer solar cells. Although there still are many challenges ahead before practical polymer solar cells will arrive in the market place, the research in functional fullerenes deserves to have more attention in order to expedite this development process.
The systematic study of the bromination of C60 was performed under various experimental conditions. Application of some chloroarenes as reaction media resulted in the high‐yield (70–96%) selective synthesis of C60Br6 and C60Br8. Direct bromination of fullerene yielded either C60Br8, C60Br14, or C60Br24 depending on the reaction time. Possible pathways of bromination of C60Br8 were analyzed using semiempirical (AM1) calculations, two most probable molecular structures are conjectured for the first isolated C60Br14.
We report Arbuzov-type reactions of chlorofullerene C(60)Cl(6) with trialkyl phosphites producing highly functionalized fullerene derivatives C(60)[P(O)(OR)(2)](5)H with high yields. The designed family of [60]fullerene phosphonic acids and their esters showed unusual properties which might find valuable material science applications.
Chlorofullerene C(60)Cl(6) undergoes highly selective reactions with thiols forming compounds C(60)[SR](5)H with high yields. These reactions open up straightforward synthetic routes to many functionalized fullerene derivatives, e.g. water-soluble compounds showing interesting biological activities.
We report a general synthetic approach to the preparation of highly functionalized amine and amino acid derivatives of [60]fullerene starting from readily available chlorofullerene C(60)Cl(6). The synthesized water-soluble amino acid derivative of C(60) demonstrated pronounced antiviral activity, while the cationic amine-based compound showed strong antibacterial action in vitro.
We report here a facile preparation of highly water-soluble derivatives C(70)[p-C(6)H(4)(CH(2))(n)COOH](8) (n = 2, 3) starting from readily available chlorinated [70]fullerene precursors C(70)Cl(8) and C(70)Cl(10). The synthesized fullerene derivatives showed pronounced antiviral activity in vitro, particularly against human immunodeficiency virus (HIV) and influenza A virus (subtypes H1N1 and H3N2).
Data on the thermal stability of energetic materials such as nitrocellulose were required in order to obtain safety information for handling, storage and usage. In present study, the thermal stability of micron and nano-sized nitrocellulose samples was determined by differential scanning calorimetry (DSC) and simultaneous thermogravimetry-differential thermal analysis (TG/DTA) techniques. The results of TG analysis revealed that the main thermal degradation of nitrocellulose occurs in the temperature range of 190-210 degrees C. On the other hand, the TG-DTA analysis of samples indicated that particle size of nitrocellulose could affect on its thermal stability and its decomposition temperature decreases by decreasing its particle size. The influence of the heating rate (5, 10, 15 and 20 degrees C/min) on the DSC behaviour of the nitrocellulose with two particle sizes was verified. The results showed that, as the heating rate was increased, decomposition temperature of the micron and nano-sized compound was increased. Also, the kinetic parameters such as activation energy and frequency factor for the micron and nano-sized nitrocellulose were obtained from the DSC data by non-isothermal methods proposed by ASTM E696 and Ozawa.
Safe storage of nitrocellulose-based propellants has become challenging due to their requirements of extreme storage and operational environments. Thus, developing new high-performance stabilizers is urgently needed to improve the stability of propellants. With their excellent thermal stability and strong ability to clear free radicals, fullerene stabilizers for nitrocellulose-based propellants were synthesized using the Prato reaction. Their molecular structures were confirmed by ¹H NMR, ¹³C NMR, FT-IR, UV–Vis, HRMS, and single-crystal X-ray diffraction. Their compatibility and stability in nitrocellulose were investigated using differential scanning calorimetry, methyl-violet, vacuum stability, and weight loss tests. Results indicated that the new fullerene stabilizers had excellent compatibility with nitrocellulose and their stability were better than the conventional stabilizers C2 and DPA. Moreover, their stability mechanism was investigated by electron paramagnetic resonance spectroscopy and FT-IR analysis. The results turned out that new fullerene stabilizers could absorb nitrogen oxides and effectively eliminate the nitroxyl radicals released from nitrocellulose decomposition. Therefore, these new multifunctional fullerene derivatives can be used as novel stabilizers and apply to single and double base propellants.
The nitrate esters are important components of double-base propellants. Aromatic amines are recommended as the stabilizers to delay the decomposition of nitrate esters and increase their storage time. The decomposition mechanisms of alkyl, alkoxy dinitrate, and poly-fluoride nitrate esters and the stabilizing effect of aromatic amines including new designed phenols are studied at the level of B3LYP/6-31G**. Alkyl and alkoxyl dinitrate esters are likely to be transformed by hydrogen abstraction, which is consistent with that of mononitrate and trinitrate esters. However, for poly-fluoride nitrate esters, NO2 catalyzed self-decomposition is preferred. In addition, comparing with mononitrate and trinitrate esters, the order of their stability is mononitrates > dinitrates > trinitrates. Poly-fluoride nitrate esters have a poorer stability than non-fluorinated nitrate esters. Comparing with parent nitrate esters, the stability of new designed poly-fluoride oxygen-containing nitrate esters is slightly improved. Aromatic amines including new designed phenols are effective stabilizers of nitrate esters, especially when introduced hydroxyl in the para position, can enhance the effects of stabilizers. The rate constants for the decomposition of nitrate esters and the bimolecular reaction between stabilizers and NO2 are calculated by using traditional transition state theory.
Comparison between the reaction energy barrier of nitrate esters and stabilizers with NO2
Radionuclide internal contamination can induce chemical and radioactive intoxication and produce harmful free radicals in vivo. At present, administration of chelating agents is the most effective treatment against nuclide contamination. However, traditional studies on chelating agents have ignored the damage caused by free radicals to the body. The present study aimed to develop a type of a bifunctional sequestering agent that can chelates nuclides and scavenges free radicals simultaneously. Therefore, a novel catechol amide-derivatized polyhydroxylated fullerene was designed and prepared. The poor water solubility of fullerene was ameliorated by chemically modifying hydrophilic catechol amide and multiple hydroxyl groups, and obtaining high water-soluble fullerene derivatives. The affinities of chelators were investigated via sulfochlorophenol competitive complexing method and antioxidant capacities were examined by electron paramagnetic resonance. The results revealed the good complexation of the designed and synthesized chelating agent with uranyl ions; and its efficiency in scavenging hydroxyl radicals. This chelating agent showed extremely low toxicity and notable protective effect against oxidative stress on A549 cells. Besides, in U(VI)-exposed A549 cells, immediate treatment with catechol amide-derivatized polyhydroxylated fullerene significantly decreased the lactate dehydrogenase (LDH) release by inhibiting the cellular U(VI) intake, promoting the intracellular U(VI) release and inhibiting the production of intracellular reactive oxygen species (ROS). These results suggest that this fullerene derivative may be a valuable in vivo antioxidant and radionuclide decorporation agent.
In this study, microcrystalline cellulose nitrate (MCCN) as energetic polymer is successfully obtained from Posidonia oceanica brown algae (POBA). Fourier transform infrared spectroscopy (FTIR) results show alterations in the intensities of some absorption bands, suggesting a significant difference in the chemical structure between microcrystalline cellulose and the emergent MCCN samples. X‐ray diffraction (XRD) measurements indicate that MCCNs are more crystalline than conventional nitrocellulose (NC). According to scanning electron microscopy (SEM), both NC and MCCN reveal a compact structure and a rough surface. Differential scanning calorimetry (DSC) displays that the thermal degradation of MCCNs shifts to lower temperatures compared to the respective NCs. Furthermore, in comparison with NC samples, MCCN samples exhibit high density, high nitrogen content, low viscosity‐average molecular weight, and good thermal stability. On the other hand, kinetic modeling based on DSC data is carried out by isoconversional integral methods to determine Arrhenius parameters and the decomposition mechanisms. It is found that MCCNs present lower activation energies than conventional NCs with a decrease of ≈6%. Finally, this work opens a new pathway to prepare MCCN from POBA, and it is expected to have applications in several areas such as propellants, energetic binders, and gas generators.
Recently, the eutectic composition of organic binary mixtures MENA+DPA has been found to be an efficient stabilizer of nitrocellulose. However, the behavior of such new stabilizer must be further investigated, especially after a long period of storage of the energetic composition. In this study, the stabilizing effect of the eutectic MENA+DPA on NC stability during artificial aging (at 338.65 K for 120 days), compared to its pure components, has been investigated by conventional stability tests and kinetic modeling. According to Bergmann & Junk (T = 405.15 K) results and over the entire period of aging, the eutectic MENA+DPA exhibits the best stabilizing effect on NC. The vacuum stability test (T = 353.15, 363.15, 373.15, and 383.15 K) results revealed that the amount of the evolved gas of NC containing this eutectic composition is very close to that of DPA, known as the conventional stabilizer. Furthermore, the kinetic modeling on VST data, obtained at four isothermal temperatures, was performed by two different methodolo-gies, viz, fitting and free models to determine the kinetic triplets, which have been subsequently used to predict the storage lifetime for the studied systems. It was found that the NC stabilized by the eutectic presents the highest value of the activation energy and has the longest storage lifetime during the entire heating period corroborating the stability tests results and affirming the excellent stabilizing effect of this mixture with respect to its pure component even if a long storage period is expected.
In this paper, the compatibility of nitrocellulose (NC) with some aniline‐based stabilizers was studied in order to detect any interaction between these materials. Both thermal techniques [differential scanning calorimetry (DSC) and vacuum stability test (VST)], and supplementary non‐thermal techniques [Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and densimetry] were used. The thermal and non‐thermal measurements showed that NC was highly compatible with N‐(2‐methoxyethyl)‐p‐nitroaniline (MENA) and diphenylamine (DPA), while a degree of incompatibility is indicated for N‐(2‐acetoxymethyl)‐p‐nitroaniline (ANA). The compatibility of the different mixtures was further probed by the kinetic investigation, and the activation energy and the pre‐exponential factors were computed. A detailed discussion and comparison of the compatibility results from all the methods are made. Despite aniline‐based compounds have exhibited a best stabilizing effect on the stability of nitrate esters. It was demonstrated here that some aniline‐based compound could not be used since some compatibility issues are found using various analytical techniques such as thermal, FTIR and XRD tools as well as the kinetic investigation using VST.
Nitrocellulose (NC) was investigated via an improved isothermal decomposition dynamics research instrument at temperature intervals from 378.15 to 398.15 K. Arrhenius equation and model-fitting method were used to calculate the thermal decomposition kinetic parameters. Results of these approaches were consistent, with an average E a of 144.7 kJ mol ⁻¹ and lnA of 27.39. The storage life of NC was estimated using the Berthelot equation. Results showed that the effective storage life of NC at ambient temperature (298.15 K) was extrapolated to 10.57 years with the extent of reaction reaching 0.1% and 52.91 years with the extent of reaction reaching 0.5%. The thermodecomposition gas and residues of NC were verified by GC, FT-IR, and SEM. The possible reaction mechanism of the isothermal decomposition of NC was provided.
The effect of organic eutectic mixture of diphenylamine (DPA) and N-(2-methoxyethyl)-p nitroaniline (MENA) with respect to its pure components on the stability of nitrocellulose (NC) has been investigated by means of stability tests and kinetic modeling. The prepared mixtures have been analyzed by FTIR, XRD, and DSC. The obtained results showed that the eutectic composition does not reveal any compatibility issue with NC. The Bergmann-Junk and Vacuum Stability Test results demonstrated that all samples are stable. The NC stabilized by the eutectic mixture (DPA +MENA) displayed the best stabilizing effect compared to that stabilized by the pure components. Furthermore, kinetic modeling has been carried out by isoconversional analysis to determine the kinetic triplet. It was found that the NC stabilized by the eutectic mixture presents the highest average activation
energy, what corroborating the stability tests results and justifying the potential of such eutectic composition as efficient NC stabilizer.
A convenient and highly efficient palladium-catalyzed reaction of [60]fullerene (C60) with aroyl compounds via enolate-mediated C-H activation and hydroxylation have been exploited for the first time to synthesize novel C60-fused dihydrofurans, and rare 1,4-fullerenols. Further functionalization including etherification, and esterification of synthesized 1,4-fullerenols provided efficient access to versatile fullerene derivatives. Moreover, a plausible reaction mechanism leading to the observed products is proposed.
The review is devoted to the use of halogenated fullerenes as precursors for the synthesis of functional derivatives of fullerenes C60 and C70. Data on chemical transformations of halogenated fullerenes C60Cl6, C70Cl8, C70Cl10, C60F18, C60F36 and C60F48 are described systematically, with the focus being placed on the preparation of compounds with valuable properties. In particular, new approaches to the synthesis of water-soluble fullerene derivatives are considered and prospects for their practical use in biomedicine are evaluated.
The bibliography includes 108 references.
The propellants of nitrate esters can be stabilized by some aromatic amines practically. To probe the mechanism of this phenomenon, we performed DFT calculations on: (1) The decompositions of nitrate esters (with and without the catalysis of NO2) and (2) the reaction between the stabilizers and the nitro dioxide (NO2 is released during the storage of nitrate esters). The structures on the reaction paths (reactants, intermediates and products) were optimized at the (U)B3LYP/6-31G** level. It was shown that NO2 lowers the activation energy barrier in the decomposition of nitrate ester by 11.82-17.86 kJ/mol and efficiently catalyzes the rupture of O-NO2 bond. However, the aromatic amines, typical stabilizers for nitrate esters, can easily eliminate NO2 with activation barriers as low as 27–113 kJ/mol (with one exception of 128 kJ/mol). These values are, for most cases, lower or much lower than the activation energy barriers for reactions between nitrate esters and NO2 (127–137 kJ/mol). Consequently, the stabilizers can block the NO2 catalysis for the decompositions of nitrate esters.
Hexachloro[60]fullerene, C60Cl6, was reacted with a mixture of ROH/H2O (R = Me, Et, n-Pr, (CH2)(2)C CH) to form both C60Cl(OH)(OR)(4) and C60Cl(OR)(5). Only the C60Cl(OH)(OR)(4) were isolated with bulky alcohols, ROH (R = (CH2)(3)C CH, (CH2)(4)C CH). Tetrahydro[60]fullerene epoxides, C-60(O)(OR)(4), were prepared by treating C60Cl(OH)(OR)(4) with CuI. The epoxy moiety could be hydrolyzed to the vicinal diol derivatives, C-60(OH)(2)(OR)(4), and then oxidized to form dicarbonyl open-cage fullerenes, C60O2(OR)(4). CuI was found to convert the terminal alkynyl addends into iodoalkynyl addends on the C-60 cage.
Although N-methyl-P-nitroaniline (MNA) was a quite effective stabilizer in composite modified double base (CMDB) propellants, it undergoes crystallization easily from nitroglycerin (NG) during storage. In order to improve its solubility in nitroglycerin (NG) and the stability in propellants, several new stabilizers including N-ethyl-p-nitroaniline (ENA), N-n-propyl-p-nitroaniline (n-PNA), N-i-propyl-p-nitroaniline (i-PNA), N-n-butyl-p-nitroaniline (n-BNA) and N-t-butyl-p-nitroaniline (t-BNA) were designed and synthesized to replace MNA by increasing the carbon chain length. The interaction between NG and different stabilizers was simulation by Materials Studio 5.5 and the stability and the high temperature stability performance of those new stabilizers in propellants were calculated by Gaussian 09. It was found that both the solubility of new stabilizers in NG and the stability and the high temperature stability performance of those in propellants were improved when the carbon chain length of substitution groups on nitrogen atom was increased. Thus, the n-BNA was a most potential stabilizer. Then all properties of the stabilizers were studied experimentally, which was agreement well with the theoretical analysis.
Propellants containing nitrocellulose (NC) continuously decompose. The decomposition products released in the process increase the rate of the decomposition and a self-accelerating behavior is obtained. To prevent the autocatalysis, stabilizers are added to NC/NG-based propellants. The action of the stabilizers is to trap the nitrous decomposition products and form stable compounds, which prevent or delay further decomposition. The most common stabilizers are aniline derivatives, which can form potentially toxic and/or carcinogenic nitrosamine derivatives during prolonged storage in propellants. This work is the joint effort between the Swedish Defence Research Agency (FOI) and Eurenco Bofors (EuB) to find new stabilizers without any amine moiety to avoid nitrosamine formation, which has resulted in a new class of stabilizers with plasticizing properties. The paper describes the concept of this class of plasticizing stabilizers, the synthesis of these compounds and characterization of their performance as stabilizers. The most promising stabilizer was found to be bis(2,6-dimethoxyphenyl)triethyleneglycol (Stab-5). Kilogram scale production of this substance at FOI allowed evaluation of its stabilizing effect in real propellants and its effect on the burning rate in a double-base rocket motor at EuB. Accelerated ageing of a double-base propellant stabilized with Stab-5 was applied in order to identify the compounds that were obtained in the reaction between the stabilizer and the decomposition products.
We report novel synthetic routes for facile preparation of highly functionalized fullerene derivatives C60(OR)5X (X = H, Cl, Br), C60(OR)4O and C60(OR)2 from chlorofullerene C60Cl6. The first water-soluble fullerene compound bearing residues of 3-oxypropanoic acid demonstrated a potent anti-HIV activity.
Labile bis-triazoline adducts of C60 are supposed to be the precursors of bis-azafulleroids, but the formation mechanism is still unclear because of the incomplete isolation of the thermolized products and the lack of X-ray structures. A rigid-tethered reagent 1,2-bis(azidomethyl)benzene (1) was used to regioselectively synthesize the labile 1,2,3,4-bis(triazolino)[60]-fullerene (2), the structure of which was determined by single-crystal X-ray crystallography. Further thermolysis of 2 produces four products (3 a–3 d), which were all characterized by X-ray crystallography. Although 3 a and 3 b have traditional bis-azafulleroid structures, as proposed previously, 3 c and 3 d show unprecedented structures with either the coexistence of [5,6]-open and [6,6]-closed patterns or an oxidized structure with an 11-membered ring on the cage. A thermolysis mechanism is proposed to clarify long-term confusion about the transformation process from bis-triazoline adducts to bis-azafulleroids of C60.
The effect of chemical stabilizer and their stability mechanism in double-base solid propellants were reviewed from the aspect of the structure, characteristics, application and mechanism of chemical stabilizer. The problems in recent studies, including the lack of study on relationship between structure and characteristics of chemical stabilizer, insufficient study on their mechanism, and improvement of test methods for thermal stability, were analyzed. The future trend should focus on understanding the relationship between structure and characteristics of chemical stabilizers, studying their reaction mechanism and kinetics, and developing the application of new techniques and new methods, etc. with 74 references. ©, 2015, China Ordnance Industry Corporation. All right reserved.
The surveillance of gun propellants is basically performed either by an investigation into the thermal behavior of the propellant or by the determination of its remaining effective stabilizer content. Over the years it is shown that the surveillance of NC based gun propellants is necessary. NC based materials are intrinsically unstable, and can cause many accidents. Some accidents were caused by old unstable material, other ones were initiated by the extreme conditions during storage, like during expeditionary operations of military forces. And in quite a few cases it was a combination of these. Surveillance tests have changed over the years, and the last philosophy is to test the propellants as close as possible in comparison to the way they are stored [1] for this way of testing the Heat Flow Calorimetry (or microcalorimetry) method is the optimum. Older methods like the Abel heat test, Methyl Violet Test, Bergman-Junk stability test, are test methods an analysis of the current status, without or very limited prediction behavior. Besides that the temperatures are relatively high, the measuring value is quite strongly dependent of the observer/operator. In general these tests are applied for propellants and sometimes explosives, although the general application worldwide (as far they are in use by countries) is propellants.
A reaction of 3,3’,4,4’-tetrakis(methoxycarbonyl)benzophenone tosylhydrazone with fullerene C60 was used to obtain a novel methano-[60]fullerene derivative bearing four carboxylic groups, whose sodium and potassium salts are water-soluble. The compound possesses antiviral and anticancer activity as well as pronounced antioxidant properties in combination with a low toxicity.
In the previous study, it was observed that the stability of nitrocellulose (NC) cannot be determined by thermal analyses such as differential scanning calorimetry (DSC) at heating rates of 1–10 K/min. This was because the thermal curves of NC samples with different stabilities could not be distinguished from one another. In this study, we explain why such thermal analyses cannot be used to evaluate the thermal stability of NC and identify the conditions under which thermal analyses can be used for this purpose. We investigated the effect of heating rate on the thermal behavior of pure NC and NC stabilized with diphenylamine (DPA) or akarditeII (AKII), which is a conventional stabilizer, by using the heat flux calorimeter (C80). At high heating rates (0.2–0.3 K/min), only single exothermic peak was observed in the thermal curves of both pure NC and NC/DPA and the thermal curve of pure NC was practically similar to that of NC/DPA. At low heating rate (0.02 K/min), two exothermic peaks were observed for both pure NC and NC/DPA. The heat amount of the first peak depended on the partial pressure of O2 in the atmosphere. The first peak in the thermal curve of NC/DPA was slightly suppressed as compared to that of pure NC. These results indicate that the stability of NC probably depends on the first exothermic peak that represents oxidation of NC by atmospheric O2. From this, on the thermal analyses at high heating rates, thermal curves of pure NC and NC/DPA could not be distinguished from one another. This is because the decomposition of NC itself occurs in the second exothermic peak before the oxidation of NC by atmospheric O2 in the first peak, which is attributed to the stability of NC. The results of the thermal analyses under isothermal conditions at 393 K in an O2 atmosphere revealed that the induction period of NC/DPA and NC/AKII was longer than that of pure NC. From these results, it is speculated that the stability of NC can be evaluated by thermal analyses carried out under O2-rich conditions at low heating rates.
Since their first detection and bulk production, the fullerenes have
gained a primary role on the scientific scene, reaching their climax when
the 1996 Nobel Prize for Chemistry was awarded to Kroto, Curl and Smalley
for their seminal discovery. The unique physical and chemical properties
of these new forms of carbon led many scientists to predict several
technological applications. This created a heavy disappointment when it
was clear that fullerene-based materials would not soon be ready for the
market. However, the fullerenes have so far delighted several dozens of
researchers who found that C
60
and its relatives undergo a
variety of chemical reactions. In most cases, the new derivatives retain
the main properties of the original fullerene, and it is now not unlikely
that some functionalized fullerenes may find useful applications in the
field of materials science and technology. In this Article we summarize
the basic principles of the organic chemistry of fullerenes, together with
a description of the physicochemical properties that have made these
carbon cages popular in materials science, and review the most recent
achievements in the functionalization of fullerenes aimed at the
production of new molecular materials.
An efficient aqueous acid chemistry for the preparation of fullerols, consisting of 14–15 hydroxy moieties in an average structure, from C60 molecules is described.
In this work, five akardite‐II (AK‐II) daughter products were produced and isolated. Their respective MS, NMR, IR and UV spectra were recorded. These five products were positively identified as: N‐NO‐AK‐II, 2‐NO 2 ‐AK‐II, 4‐NO 2 ‐AK‐II, N‐NO‐2‐NO 2 ‐AK‐II and N‐NO‐4‐NO 2 ‐AK‐II. An HPLC method giving baseline separation of 6 AK‐II family products and 10 diphenylamine (DPA) family products is also described. Finally, preliminary results concerning the stability of AK‐II daughter products are discussed.
It was shown for the first time that reactions of C60 halides with aliphatic amines provide a facile route for the synthesis of aminofullerenes, valuable precursors for water-soluble cationic fullerene derivatives. Particularly, chlorofullerene C60Cl6 and N-substituted piperazines were investigated in this work. It was shown that substitution of chlorine atoms in C60Cl6 by amine groups is accompanied by partial elimination of addends from the fullerene cage that yields mixtures of di-, tetra- and, hexaaminofullerenes as the final products. Separation of these mixtures by column chromatography resulted in isolation of pure 1,4-diaminofullerenes; this procedure gives much higher and more reproducible yields of these compounds than direct oxidative photoaddition of secondary amines to C60. ESI mass spectrometry and NMR spectroscopy data showed that hexaaminofullerene isomers are major components in inseparable mixtures of polyaddition products. Polyaminofullerenes were found to be readily soluble in aqueous acids; these solutions are unstable because of a facile substitution of protonated amine groups with hydroxyls. Nevertheless, the use of other amine substrates in the investigated reaction can potentially allow the preparation of more stable water-soluble cationic fullerene derivatives for biological studies.
A chemical review provides a comprehensive survey of the applications that the radical reactivity of fullerenes (C60) has found in various fields ranging from synthetic organic chemistry and material sciences to biomedicine. The latest advances in the field of synthetic organic chemistry have enabled the development of appropriate reaction protocols that allow for selective preparation of structurally diverse monoaddition fullerene adducts or multiadducts, with well-defined addition patterns. These developments have renewed interest in the radical chemistry of fullerenes, particularly in the synthesis of novel architectures with potentially important applications. Fullerenes have also shown to exhibit stronger antioxidant performance than leading antioxidants such as vitamin E.
Initially envisaged as rather unreactive, aromatic-like molecules, the fullerenes instead undergo a wide variety of reactions characteristic of alkenes. The many derivatives of C60, and the few of C70, that have now been reported offer new directions for organic chemistry.
Thermogravimetric studies were carried out with double base propellants to find out the rate-determining stage and to understand the mechanism. The decomposition process can be divided into 3 stages as follows: Diffusion of nitroglycerin takes place in the temperature range 120°C–160°C. Two processes occur in the temperature range 170°C–205°C, namely the dissociation of nitroglycerin and the cleavage of the CO bond, the later being the rate-determining step. The cleavage of the CO bond is followed by a considerable decomposition of nitrocellulose.
Mechanismus der thermischen Zersetzung von Doublebase-Treibstoffen
Thermogravimetrische Untersuchungen wurden mit Doublebase-Treibstoffen durchgeführt, um den geschwindigkeitsbestimmenden Verlauf und den Mechanismus herauszufinden. Der Zersetzungsprozeß kann in drei Stufen unterteilt werden: Diffusion von Nitroglycerin, dies tritt ein im Temperaturbereich 120°C–160°C. Im Temperaturbereich 170°C–205°C laufen zwei weitere Reaktionen ab, nämlich die Aufspaltung von Nitroglycerin und die Spaltung der CO Bindung in der Nitrocellulose, wobei die letztere Reaktion die geschwindigkeitsbestimmende ist. Durch die Spaltung der CO Bindung wird die Nitrocellulose in erheblichem Maße zersetzt.
Mécanisme de la décomposition thermique des propergols à double base
Des propergols à double base ont été soumis à des analyses par thermogravimétrie pour déceler les facteurs qui déterminent la vitesse et le mécanisme de décomposition. On peut discerner trois phases dans le processus de décomposition: la diffusion de la nitroglycérine qui se produit entre 120°C et 160°C; ensuite, entre 170°C et 205°C se produisent deux autres réactions, à savoir la dissociation de la nitroglycérine et la rupture de la liaison CO dans la nitrocellulose, cette dernière déterminant la vitesse de décomposition. La rupture de la liaison CO se traduit par une forte décomposition de la nitrocellulose.
Three nitrocellulose-based propellants for use in micro gas generators equipped with different stabilizing systems have been investigated to assess the stabilization capability with regard to in-service time, whereby strong time–temperature profiles have been applied. The three stabilizing systems have been (i) 0.74 mass-% diphenylamine (DPA) and 0.48 mass-% Akardite II (Ak II); (ii) 1.25 mass-% Ak II; (iii) 2.04 mass-% Ak II. Several profiles were considered. Two simulate the heating at sun exposure in hot areas, others consider environmental temperatures in hot-humid and hot-dry areas. They were evaluated according to the load and finally one was chosen for the assessment. The contents of stabilizers were determined by high performance liquid chromatography after Soxhlet type extraction. To describe stabilizer consumption, the most suitable kinetic model was taken. Therewith a prediction was made using the chosen time–temperature profile named ‘Phoenix’, designed for temperatures at the steering wheel. The objective was to reach with this profile 15 years until the consumption of primary stabilizer content. This is conservative, because with the stabilizing action of the consecutive products of the stabilizers longer times are possible.
Reaction of C60Cl6 with organic cyanide yielded an ionic salt comprising the fullerene anion [C60(CN)5]–. This anion showed unprecedented stability in air and in solutions in the presence of water, organic and inorganic acids, and various electrophiles. The remarkable stability of the [C60(CN)5]– anion opens wide opportunities for the design of various air-stable salts incorporating different cations (metallocene, tetrathiafulvalene, and etc.) that might reveal valuable magnetic or electronic properties and find wide application in the field of material science.
A solid rocket propellant based on glycidyl azide polymer (GAP) binder plasticized with nitrate esters and oxidized with a mixture of ammonium nitrate (AN) and triaminoguanidine nitrate (TAGN) and including non-lead ballistic modifiers, was formulated. The propellant was designed so as to produce non-acidic and non-toxic exhaust products while still providing reasonably good burning rate and impulse. This propellant was characterized with respect to thermal and chemical stability and storage life by a variety of test methods. The data indicate that the propellant exhibits good stability and is suitably safe for prolonged storage. Characterization data for this propellant with regard to processing parameters, tensile properties, and ballistic performance are presented in a companion paper.
Triphenylamine (TPA) was used for the first time in France in 1937 as a stabilizer for propellants. The stability of those samples was described as 'good'. Around 1950 an American group produced TPA stabilized propellants and investigated the decomposition mechanism. Apart from one single experiment in the 1970s no further attempts were made to take TPA as a stabilizer for propellants. With the background of an increasingly critical discussion about nitrosamines in propellants and their declaration of being carcinogenic, TPA revealed a renaissance since the year 2000. To achieve the goal of nitrosamine free propellants several TPA stabilized propellants were produced. Their processability, stability and ballistic properties were investigated. This publication summarizes the most important results of stability tests on more than 30 different TPA stabilized propellants including the decomposition mechanism, the synthesis of the consecutive products and their stabilizing properties. In addition, the internal compatibility of TPA with the most important propellant ingredients is discussed and its relative decomposition rate is compared with that of other stabilizers. In summary TPA is a suitable stabilizer for propellants. It has nevertheless two disadvantages: It is relatively rapidly consumed in double base formulations (which makes it difficult to pass the criteria of AOP-48, Ed. 2) and the stabilizing activity of the two major consecutive products 4-NO2-TPA and especially 4,4'-diNO(2)-TPA is low.
The reactions of alkyl peroxyl radicals with cellulosic and lignin-containing papers have significance in both the problems
of brightness reversion and paper aging phenomena. Since transient peroxyl radicals are elusive to ESR and other spectroscopic
detection, we have explored the controlled study of the interactions of nitrogen oxides with paper and some model lignin compounds
in solution as a comparable model of free radical oxidation. Formations of intermediate iminoxyl and nitroxide radicals are
identified by ESR with products in some model systems analysed by GC/MS to elucidate the primary mechanisms of the interactions
of these gaseous free radicals with papers and with some simple organic model lignin compounds.
The fullerene family, and especially C(60), has delighted the scientific community during the last 25 years with perspective applications in a wide variety of fields, including the biological and the biomedical domains. Several biomedical uses have been explored using water-soluble C(60)-derivatives. However, the employment of fullerenes for drug delivery is still at an early stage of development. The design and synthesis of multifunctionalized and multimodal C(60) systems able to cross the cell membranes and efficiently deliver active molecules is an attracting challenge that involves multidisciplinary strategies. Promising results have emerged in the last years, bringing fullerenes again to the front of interest. Herein, the state of the art of this emerging field is presented and illustrated with some of the most representative examples.
The palladium-catalyzed reaction of [60]fullerene with a variety of readily available anilides, initiated by C-H bond activation and followed by cyclization, afforded [60]fulleroindolines in a highly regioselective manner. A plausible reaction mechanism was proposed.
We present results on a new fullerene-based anchoring group for molecular electronics. Using lithographic mechanically controllable break junctions in vacuum we have determined the conductance and stability of single-molecule junctions of 1,4-bis(fullero[c]pyrrolidin-1-yl)benzene. The compound can be self-assembled from solution and has a low-bias conductance of 3 x 10(-4) G0. Compared to 1,4-benzenedithiol the fullerene-anchored molecule exhibits a considerably lower conductance spread. In addition, the signature of the new compound in histograms is more significant than that of 1,4-benzenediamine, probably owing to a more stable adsorption motif. Statistical analyses of the breaking of the junctions confirm the stability of the fullerene-gold bond.