Copper(I) Bromide: An Alternative Emitter for Blue‐Colored Flame Pyrotechnics

Copper(I) bromide was evaluated as an alternative emitter for blue flame pyrotechnic compositions. CuBr and CuCl emission spectra were recorded from a butane torch flame and compared. Cu(BrO₃)₂ was synthesized and used in pyrotechnic compositions as an oxidizer and the source for the generation of CuBr species. Pyrotechnic compositions, which contained copper and potassium bromates as oxidizers, were optimized for the generation of blue flames. The experimental data, including emission spectra of the flames, chromaticity coordinates, burning rates, luminous intensities, and sensitivity tests, were analyzed and compared.     

Green Colorants Based on Energetic Azole Borates

The investigation of green‐burning boron‐based compounds as colorants in pyrotechnic formulations as alternative for barium nitrate, which is a hazard to health and to the environment, is reported. Metal‐free and nitrogen‐rich dihydrobis(5‐aminotetrazolyl)borate salts and dihydrobis(1,3,4‐triazolyl)borate salts have been synthesized and characterized by NMR spectroscopy, elemental analysis, mass spectrometry, and vibrational spectroscopy. Their thermal and energetic properties have been determined as well. Several pyrotechnic compositions using selected azolyl borate salts as green colorants were investigated. Formulations with ammonium dinitramide and ammonium nitrate as oxidizers and boron and magnesium as fuels were tested. The burn time, dominant wavelength, spectral purity, luminous intensity, and luminous efficiency as well as the thermal and energetic properties of these compositions were measured.     

"Green" pyrotechnics: a chemists' challenge

Fireworks are probably the application of chemistry which resonates best with the general public. However, fireworks and (civil and military) pyrotechnic applications cause environmental pollution and thus have given rise to the development of new, environmentally friendly pyrotechnic compounds and formulations. Nitrogen-rich energetic materials, such as the derivatives of tetrazoles and tetrazines, are about to revolutionize traditional pyrotechnic compositions. This Review summarizes the sources of pollution in current formulations and recent efforts toward "green" pyrotechnics.     

Perchlorate‐Free Pyrotechnic Formulations Utilizing Energetic Chlorine Donors: 1‐CDN, 11‐CDN, 13‐CDN

Several novel materials were investigated as energetic chlorine donors, specifically for the preparation of perchlorate‐free pyrotechnic formulations with low‐smoke output. The novel compounds, 2‐chloromethyl‐2‐methyl‐5,5‐dinitro‐1,3‐dioxane (1‐CDN), 2,2‐bis(chloromethyl)‐5,5‐dinitro‐1,3‐dioxane (13‐CDN), and 2‐(dichloromethyl)‐2‐methyl‐5,5‐dinitro‐1,3‐dioxane (11‐CDN), were formulated with a variety of fuels and oxidizers and their resulting colored flames analyzed for color quality. The preparation and preliminary characterization of these energetic chlorine donors are described.     

A Strontium‐ and Chlorine‐Free Pyrotechnic Illuminant of High Color Purity

The development of a red‐light‐emitting pyrotechnic illuminant has garnered interest from the pyrotechnics community owing to potential regulations by the United States Environmental Protection Agency (U.S. EPA) regarding the use of strontium and chlorinated organic materials. To address these environmental regulatory concerns, the development of lithium‐based red‐light‐emitting pyrotechnic compositions of high purity and color quality is described. These formulations do not contain strontium or chlorinated organic materials. Rather, the disclosed formulations are based on a non‐hygroscopic dilithium nitrogen‐rich salt that serves as both oxidizer and red colorant. These formulations are likely to draw interest from the civilian fireworks and military pyrotechnics communities for further development as they both have a vested interest in the development of environmentally conscious formulations.     

Brighter‐ and Longer‐Burning Barium‐Free Illuminants for Military and Civilian Pyrotechnics

The development of barium‐free pyrotechnic illuminants is described. Heavy metal barium nitrate oxidizer and strontium nitrate oxidizer were replaced with sodium nitrate to adequately address environmental concerns while providing the brightest possible illuminant. The new formulations further address environmental concerns and mitigate single‐point‐of‐failure through the replacement of polyester‐based Laminac 4116/Lupersol binder system with the epoxy‐based Epon 813/Versamid 140 binder system. The new formulations were found to burn longer and brighter than the control with a low sensitivity to various ignition stimuli.     

High‐Performing Red‐Light‐Emitting Pyrotechnic Illuminants through the Use of Perchlorate‐Free Materials

The development of perchlorate‐free M662 40 mm illuminating pyrotechnic compositions is described. On the bases of cost, performance, and sensitivity, potassium periodate was determined to be most effective potassium perchlorate replacement in the compositions tested. The optimal periodate‐based composition exceeded the performance of the perchlorate‐containing control, exhibited low sensitivity values to impact, friction, and electrostatic discharge, and had high thermal onset temperatures.     

The influences of combinative effect of temperature and humidity on the thermal stability of pyrotechnic mixtures containing strontium nitrate as oxidizer

The influences of combinative effect of temperature and humidity on the thermal stabilities of three pyrotechnic compositions are investigated in the study. The thermal behavior for each pyrotechnic is analyzed by SETARAM thermal analyzer. Activation energy is determined by Kissinger method and critical temperature of thermal explosion (T _b) of pyrotechnic compositions is also calculated. The results of thermal analysis revealed that relative humidity could decrease the thermal stability of pyrotechnic mixtures. The critical temperature of thermal explosion (T _b) of each pyrotechnics decreased as the relative humidity increasing. Based on the value of T _b, the thermal stabilities of the pyrotechnic mixtures are in the order of S_r(NO₃)₂/Mg₄Al₃/PVC/PF > S_r(NO₃)₂/S_rCO₃/KClO₄/Mg₄Al₃/PVC/PF > S_r(NO₃)₂/KClO₄/Mg₄Al₃/PVC/PF. The thermal stability of S_r(NO₃)₂/Mg₄Al₃/PVC/PF show the best thermal stability than other two mixtures whether it is in the condition of humidity or not.     

Chlorine‐Free Red‐Burning Pyrotechnics

The development of a red, chlorine‐free pyrotechnic illuminant of high luminosity and spectral purity was investigated. Red‐light emission based solely on transient SrOH_(g) has been achieved by using either 5‐amino‐1H‐tetrazole or hexamine to deoxidize the combustion flame of a Mg/Sr(NO₃)₂/Epon‐binder composition and reduce the amount of both condensed and gaseous SrO, which emits undesirable orange‐red light. The new formulations were found to possess high thermal onset temperatures. Avoiding chlorine in these formulations eliminates the risk of the formation of PCBs, PCDDs, and PCDFs. This finding, hence, will have a great impact on both military pyrotechnics and commercial firework sectors.     

High-nitrogen-based pyrotechnics: longer- and brighter-burning, perchlorate-free, red-light illuminants for military and civilian applications

The full-up prototype testing of perchlorate-free, hand-held, signal illuminants for the US Army's M126A1 red star parachute hand-held signal is described. Compared to the perchlorate-containing control, the disclosed illuminants yielded excellent stabilities toward various ignition stimuli while offering superior pyrotechnic performance. Militarily, the illuminants provided further evidence that development of smaller hand-held signal items in an environmentally conscious way is a realistic and obtainable goal. The results are also important from the perspective of civilian fireworks, as the development of brighter, longer-burning, and environmentally compatible red-light-emitting pyrotechnics is now possible.     

A study on kinetics of ignition reaction of B4C/KNO3 and B4C/KClO4 pyrotechnic smoke compositions

Journal of Thermal Analysis and Calorimetry - Presented herein is a study on the ignition reaction kinetics and mechanism of B4C/KNO3 and B4C/KClO4 pyrotechnic smoke compositions using the...     

Studies on the ageing of a magnesium-strontium nitrate pyrotechnic composition using isothermal microcalorimetry and thermal analysis techniques

The ageing behaviour of a pyrotechnic composition containing equal parts by mass of magnesium and strontium nitrate has been followed by isothermal microcalorimetry. The measurements were carried out on the samples at 50 °C and 65% relative humidity in air using closed ampoules. The results have been compared to those obtained for magnesium powder under the same conditions. Following an initial induction period, the pyrotechnic compositions reacted at a much faster rate than magnesium powder alone. The main reaction products were found to be magnesium hydroxide and strontium nitrite; the amounts formed have been correlated with the cumulative heats of ageing. In addition, the influence of the ageing process on the pyrotechnic reaction has been studied by high temperature differential scanning calorimetry (DSC) and by modulated temperature DSC.     

Metal‐ and Reagent‐Free Dehydrogenative Formal Benzyl–Aryl Cross‐Coupling by Anodic Activation in 1,1,1,3,3,3‐Hexafluoropropan‐2‐ol

A selective dehydrogenative electrochemical functionalization of benzylic positions that employs 1,1,1,3,3,3‐hexafluoropropan‐2‐ol (HFIP) has been developed. The electrogenerated products are versatile intermediates for subsequent functionalizations as they act as masked benzylic cations that can be easily activated. Herein, we report a sustainable, scalable, and reagent‐ and metal‐free dehydrogenative formal benzyl–aryl cross‐coupling. Liberation of the benzylic cation was accomplished through the use of acid. Valuable diarylmethanes are accessible in the presence of aromatic nucleophiles. The direct application of electricity enables a safe and environmentally benign chemical transformation as oxidizers are replaced by electrons. A broad variety of different substrates and nucleophiles can be employed.     

The Lithium Salts of Bis(azolyl)borates as Strontium- and Chlorine-free Red Pyrotechnic Colorants

After concerns regarding the use of chlorinated material for pyrotechnic items had reinforced, the action of the U.S. Environmental Protection Agency on health concerns about strontium ushered in a new era in the production of red light. Lithium was shown to impart red color to a pyrotechnic flame, however only a very narrow selection of such formulations can be found in the literature. Dihydrobis(azolyl)borates are a well investigated, easily accessible class of materials which have been proven to be suitable as pyrotechnic coloring agents. With their high nitrogen contents such moieties should also meet the requirements of a low combustion temperature and a reducing flame atmosphere for a lithium-based red-burning composition. This work evaluates the capability of the lithium salts of dihydrobis(pyrazol-1-yl)borate, dihydrobis(1,2,4-triazol-1-yl)borate, and dihydrobis(tetrazol-1-yl)borate to serve as red color imparters. The latter compounds were characterized by multinuclear NMR experiments, IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction and were investigated with respect to their thermal stabilities as well as sensitivities toward various ignition stimuli.     

Polynitroethyl‐ and Fluorodinitroethyl Substituted Boron Esters

The reaction of boron oxide with various nitro‐substituted ethanols (2‐nitroethanol, 2‐fluoro‐2,2‐dinitroethanol, 2,2,2‐trinitroethanol) furnished the corresponding nitroethyl borates B(OCH₂CH₂NO₂)₃ ( 1 ), B(OCH₂CF(NO₂)₂)₃ ( 2 ), and B(OCH₂C(NO₂)₃)₃ ( 3 ). Fluorination of the anion [(NO₂)₂CCH₂OH]^? ( 4 ) resulted in 2‐fluoro‐2,2‐dinitroethanol ( 5 ), a precursor for 2 , and was thoroughly characterized. An interesting condensation was observed with the anion 4 to form the unusual dianion [(NO₂)₂CCH₂C(NO₂)₂]^2? ( 6 ). All compounds were fully characterized by multinuclear NMR spectroscopy, vibrational spectroscopy (IR, Raman), mass spectrometry and elemental analysis. The chemical, physical and energetic properties of 1 – 3 and 5 are reported, as well as quantum chemical calculations at the CBS‐4M level of theory to predict the enthalpies and energies of formation. X‐ray diffraction studies were performed, and the crystal structures for compounds 1 – 6 were determined and discussed thoroughly. The boron esters 1 – 3 are of interest as possible candidates for smoke‐free, green colorants in pyrotechnic applications, and in case of 2 and 3 also as promising high energy oxidizers.     

High‐Nitrogen‐Based Pyrotechnics: Perchlorate‐Free Red‐ and Green‐Light Illuminants Based on 5‐Aminotetrazole

Prototype testing of perchlorate‐free hand‐held signal illuminants for the US Army’s M126 A1 red‐star and M195 green‐star parachute illuminants are described. Although previous perchlorate‐free variants for these items have been developed based on high‐nitrogen compounds that are not readily available, the new formulations consist of anhydrous 5‐aminotetrazole as the suitable perchlorate replacement. Compared to the perchlorate‐containing control, the disclosed illuminants exhibited excellent stabilities toward various ignition stimuli and had excellent pyrotechnic performance. The illuminants are important from both military and civil fireworks perspectives, as the perchlorate‐free nature of the illuminants adequately address environmental concerns associated with perchlorate‐containing red‐ and green‐light‐emitting illuminants.     

Improving safety performance of lactose-fueled binary pyrotechnic systems of smoke dyes

The lactose/KClO₃ is a widely used pyrotechnic mixture to vaporize organic materials, such as smoke dyes. However, because of low ignition temperature of this mixture, serious precaution should be taken into account to prevent its accidental self-ignition. In order to find a safe and efficient alternative of this conventional mixture, KClO₃ has been replaced by common oxidizing agents including KMnO₄, KNO₃, KClO₄, Ba(NO₃)₂, PbO₂ and NH₄ClO₄. TG and DTA analysis have been used to obtain thermal characteristic of the mixtures. Based on ignition temperature of the pyrotechnic mixtures we can divide them into four categories as follows: (1) the mixture igniting at low temperature, i.e., at about 200 °C. (2) Moderate temperature igniting mixture, in which ignition occurs at 300–400 °C. (3) High temperature igniting mixture with ignition temperature higher than 400 °C .(4) Not igniting mixtures. Also, the apparent activation energy (E), ΔG ^#, ΔH ^#, ΔS ^# and critical ignition temperature (T _b ) of the ignition processes of low and moderate temperature igniting mixtures were obtained from the DSC experiments. Finally, among the investigated mixtures, lactose/KNO₃ can be considered as a safe and efficient pyrotechnic composition for vaporization of organic materials, such as smoke dyes, due to its moderate safe ignition temperature.     

Intermolecular interaction of a neutral polymeric bonding agent containing N-Vinylpyrrolidone units with ammonium perchlorate and Keto-RDX

The interaction of a new neutral polymeric bonding agent (NPBA) containing N-Vinylpyrrolidone units with two types of oxidizers (ammonium perchlorate and Keto-RDX) was investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). NPBA forms a layer of film on the surface of oxidizers. The paper gives hypothetical mechanisms for improving significantly mechanical properties by addition of the neutral polymeric bonding agent (NPBA).     

Feuerwerk

Pyrotechnic is an old empiric science on the borderline between chemistry, technics, chemical and process engineering and art and it maintains its position as an integral part of events in culture and tradition. This contribution presents the steps a firework has to pass to develop from mere chemistry to the final show. Some chemical background, information about pyrotechnic mixtures like black powder, firework star mixtures, oscillating mixtures like blinking stars and whistles are explained as well as the manufacture of selected pyrotechnic items. Aspects of production and handling safety of exhibition fireworks and the recent developments in legislation like the pyrotechnics directive, the CE‐ standardisation and REACH are touched. Although the commercial environment is getting tougher the fascination for the pyrotechnic phenomena are still alive and may initiate the motivation for the reader to get involved in the exciting topic of pyrotechnics and the associated fields of science.     

Liquid azide salts and their reactions with common oxidizers IRFNA and N2O4

Several imidazolium-based ionic liquid azides with saturated and unsaturated side chains were prepared, and their physical and structural properties were investigated. The reactivity of these new as well as some previously reported ionic liquid azides with strong oxidizers, N 2O 4 and inhibited, red-fuming-nitric acid (IRFNA), was studied.