Propellant Ingredients Research Articles

Rapid pyrolysis technique for determination of kinetic parameters of ammonium perchlorate decomposition

A laser pyrolyser setup is developed to achieve isothermal conditions using a heating rate of up to ∼105 °C.s−1 for rapid pyrolysis of a sample. It provides mechanistic information about the decomposition behavior of the sample during combustion, typically in the condensed phase. Typically, chemical kinetics data for condensed phase reactions during combustion is not derived from ab initio techniques, but rather by fitting the variation of linear burning rate with pressure with appropriate kinetic parameters. This leads to a wide variation of chemical kinetic parameters governing the decomposition of the same solid propellant ingredient, such as the commonly used oxidizer, ammonium perchlorate (AP). Therefore, a newly developed laser pyrolyser along with Fourier transform infrared (FTIR) spectroscopy was used to study the rapid pyrolysis of AP at 1 bar. The concentration profiles of the evolved gases were used to develop the global reaction mechanism. The global reaction mechanism that emerged is: NH4ClO4→1.09H2O+0.06HNO3+0.56NO2+0.18N2O+0.5Cl2+0.71O2+0.88H2 with pre-exponential factor (A) = 6.6×107 s−1 and activation energy (Ea) = 108 kJ.mol−1. Kinetic parameters of the same AP sample from thermogravimetric analysis are A = 5.6 ×105 s−1, and Ea = 100 kJ.mol−1. This suggests that kinetic parameters obtained from slow heating experiments predict a reaction rate significantly lower than that observed under high heating rates. Therefore, the raw data generated from rapid pyrolysis would be useful as an input to solid propellant combustion models improving their predictive capability.

Causes of Ammonium Nitrate Explosions and Handling Mechanisms – Case Study of the 2020 Beirut Lebanon Explosion

Ammonium nitrate (AN) is a chemical that is widely used in industry, for example as fertilizer in agriculture, explosives in military and civilian applications (for example in mining) or as a basic ingredient in solid propellants. However, as a dangerous chemical, storing ammonium nitrate can cause problems if not properly. The characteristics of AN have been studied extensively that pure AN is stable at room temperature but can explode when mixed with impurities in a closed space or in the presence of a heat/flame source nearby. This was proven in the explosion disaster at the Port of Beirut, Lebanon in 2020. This article was written using a systematic literature review (SLR) approach, where the data used came from articles published on Google Scholar, DOAJ, Emerald, Springer, and Science Direct with relevant keywords according to the topic. This article aims to evaluate and find out the causes of the ammonium nitrate explosion disaster in Beirut, as well as provide an analysis of suggestions for handling mechanisms so that a similar incident does not happen again. Evaluation of the cause of the explosion at the Port of Beirut, with fire/heat burning down part of the warehouse. An that was stored in a port warehouse mixed with other goods caused a large explosion which was started by a small fire in the warehouse. The explosion caused the death of 220 people, injured 6,500 people, formed a crater 140 meters deep and an earthquake measuring 3.3 on the Richter scale. This explosion is classified as the third most destructive urban explosion of all time, after the atomic bombs on Hiroshima and Nagasaki at the end of World War II. As a precaution, proper handling and storage of AN is required in accordance with international regulations. To reduce the potential danger of explosions without causing significant risks, this is done through an appropriate disposal mechanism.

Determination of burn rate affecting elements in composite solid propellant and its ingredients by microwave-induced plasma optical emission spectrometry.

A study of trace metallic elements in solid propellant and its ingredients is important and critical as they affect ballistic properties of solid rocket motor during combustion. In the present study, an attempt is made to develop a rapid, single run and cost-effective analytical technique for the routine and direct analysis of multi elements. Trace level metallic impurities (burn rate affecting elements) present in premix, cured propellant slab and propellant ingredients such as ammonium perchlorate, aluminium, aluminium oxide, dioctyladipate, hydroxy terminated polybutadiene and toluene diisoycanate sourced from different suppliers and propellant slag are determined based on a relatively recent analytical technique, microwave-induced plasma optical emission spectrometry (MIP-OES). Analytical wavelengths are selected based on the sensitivity and interference effects. Precision and accuracy of the developed test procedure for the metallic impurities are demonstrated using replicate analyses of certified calibration standards. The limit of quantification and detection of elements studied is determined. Linear regression coefficients are greater than 0.995. The results obtained demonstrate the potential of MIP-OES technique for the determination of metallic impurities of solid propellant ingredients, pre-mix, cured slab and slag of solid propellants with shortened analysis time which achieved lower detection limits, higher accuracy and better repeatability.

Investigation of the curing kinetics of polyurethane/nitrocellulose blends through FT‐IR measurements

AbstractPolyester (HTPS) based polyurethane (PU) elastomers were currently established to be effective binders for high‐energy composites with improved performances. Conventional PU binders are mostly non‐energetic materials, and consequently reduce the energy performance significantly. Nitrocellulose (NC), is an energetic polymer widely used as an ingredient in propellants, explosives, fireworks, and gas generators, it may be introduced in PU‐based compositions to overcome their performance drawback. Kinetic parameters must be specified in order to build PU binders with the most convenient and appropriate features. Therefore, the cure kinetics of polyester based polyurethane binder systems were investigated by Fourier transform infrared spectroscopy (FT‐IR) isothermal method. The polyester prepolymer (Desmophen® 1200) was cured with hexamethylene diisocyanate (HDI: Desmodur® N100) at various molar ratios (R[NCO]/[OH] = 0.6, 1, 1.25, and 1.5) and under different isothermal conditions (T = 60°C, 80°C, 100°C, and 120°C). In addition, the effect of the addition of nitrocellulose on the kinetics of polymerization of PU was investigated. The progression of the reaction was followed based on the decrease of the peak intensity of –NCO group at 2271 cm−1 as a function of the reaction time. The curing kinetic model and the apparent activation energy (Eα) were determined by the use of Kamal autocatalytic model and Friedman isoconversional method, respectively.

Burning surface formation mechanism of laser-controlled 5-aminotetrazole propellant

As an innovative propulsion technique, combustion mechanism of laser-augmented chemical propulsion has still to be ascertained. Benefiting from high nitrogen content and thermal stability, 5-aminotetrazole is a suitable ingredient for LACP. Under a flowing nitrogen environment, two kinds of unique burning surfaces were observed to occur for 5-ATZ, used as a single reacting propellant ingredient with the addition of carbon, under laser ablation. Both surfaces are hollow structures and differ by the possible presence of edges. Using micro computed tomography, the 3D perspective structures of both surfaces were revealed. Resorting to various characterization methods, a unified formation mechanism for both surfaces is proposed. This mechanism specifically applies to laser ablation, but could be crucial to common burning mechanisms in LACP.

Thermal interactions between hybrid HMX/ANPyO cocrystals and commonly used propellant ingredients

Nitramine-based composite propellants (N-CPs) are receiving significant attention in the field of solid rocket propulsion. Cyclotetramethylene tetranitramine (HMX)/2,6-diamino-3,5-dinitropyridine-1-oxide (ANPyO) cocrystals are a novel insensitive energetic material that may replace the high-energy component HMX in insensitive formulations. This study used the DSC-TG coupling technique and the in-situ FTIR technique to investigate the effects of propellant ingredients (AP, n-Al, and nano-Fe2O3) on the thermal decomposition of hybrid HMX/ANPyO. The results show that there are strong interactions among the components of these mixtures. In particular, the peak thermal decomposition temperatures of HMX/ANPyO/AP decreased by about 38.1–42.6 ​°C. In addition, the activation energy (Ea) of hybrid HMX/ANPyO cocrystals was reduced under the effects of Al and nano-Fe2O3. The hybrid HMX/ANPyO cocrystals have different flame propagation speeds, whereas the two typical binary mixtures of HMX/ANPyO/nano-Fe2O3 each have the lowest flame propagation speeds of 0.9 ​mm·s−1 and 1.0 ​mm·s−1 at ambient conditions. The flame propagation speed of HMX/ANPyO/n-Al was barely dependent on pressure, but those of HMX/ANPyO/AP and HMX/ANPyO/nano-Fe2O3 decreased with an increase in pressure.

Preparation and Characterization of Polyurethane/Nitrocellulose Blends as Binder for Composite Solid Propellants

AbstractPolyurethane (PU) elastomers are largely used in the field of high‐energy composites such as composite solid propellants (CSPs) and high‐energy polymer‐bonded explosives (PBXs) due to their distinguished characteristics. Conventional PU binders are mostly non‐energetic materials, and consequently reduce the energy performance significantly. Nitrocellulose (NC), is an energetic polymer widely used as an ingredient in propellants, explosives, fireworks, and gas generators, may be introduced in PU‐based compositions to overcome their performance drawback. In this context, PU/NC polymer blends at different mass ratios were prepared in the present work using hydroxyl‐terminated polyester prepolymer (Desmophen® 1200) and nitrocellulose (NC) by solution blending process. The physico‐chemical structure of the prepared PU/NC polymer composites were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and density measurements. The thermal decomposition behavior was investigated by differential scanning calorimetry (DSC). Based on the obtained DSC results, the Arrhenius parameters were computed by different isoconversional kinetic approaches, namely, iterative Kissinger‐Akahira‐Sunose (It‐KAS), iterative Flynn‐Wall‐Ozawa (It‐FWO) and Vyazovkin's nonlinear integral method coupled with compensation effect (VYA/CE). Additionally, in order to highlight the influence of the introduction of the NC to the binder composition on the performance of a composite propellant, the theoretical performances, namely, theoretical specific impulse, the adiabatic flame temperature, as well as the ideal exhaust gaseous species were determined based on NASA Lewis Code, Chemical Equilibrium with Application (CEA).

HTPB Heat of Formation: Literature Survey, Group Additive Estimations, and Theoretical Effects

Hydroxyl-terminated polybutadiene (HTPB) is a common ingredient in rocket propellants, but its thermochemical properties (composition, density, and heat of formation) are not well defined. A survey of the literature and thermochemical databases indicated wide ranges for these properties, especially heat of formation. Six group additive schemes were used to estimate the heat of formation of HTPB and analyze the effects of hydroxyl functionalization and curing reactions. Good agreement is observed between the methods for HTPB isomer units, but cumulative differences result in significant disparities for larger, practical polymers. Increased hydroxyl functionality and the curing reaction are predicted to yield nonnegligible decreases in the heat of formation. The heat of formation of propellant-grade, isophorone-diisocayante-cured HTPB R-45M () was computed as or . Chemical equilibrium analyses were completed for solid propellants composed of ammonium perchlorate and HTPB, and for hybrid rocket engines based on HTPB burning with liquid oxygen or nitrous oxide, where the heat of formation of HTPB was varied within a reasonable range. The chemical equilibrium analysis computations indicated that combustion gas properties and theoretical propellant performance can vary up to 5% within practical operating conditions for the range of HTPB heats of formation implemented.

Combined gas-phase electron diffraction and coupled cluster determination of the molecular structure of 3,4-dinitrofurazan - A propellant ingredient

The equilibrium molecular structure of the first pernitroheterocycle, 3,4-dinitrofurazan, in terms of the dynamic model with relaxation of all structural parameters, has been calculated for the first time using gas-phase electron diffraction (GED) with coupled cluster calculations up to CCSD(T)-AE/aug-cc-pwCVQZ level of theory. A model with C2 symmetry was found to be the best match for the observed scattering intensities. The structural parameters of 3,4-dinitrofurazan were compared to those of the parent furazan molecule calculated at the CCSD(T)-AE/aug-cc-pwCVQZ level of theory. The mean amplitudes and vibrational corrections necessary for the GED analysis were computed at the B3LYP/SNST//MP2/aug-cc-PVTZ level of theory using quadratic and cubic force fields. With the help of several topological, magnetic, and orbital descriptors, peculiar characteristics of the electronic and geometric structure of 3,4-dinitrofurazan were studied. Comparison of the structures obtained at the CCSD(T)-AE/aug-cc-pwCVQZ and CCSD(T)-AE/cc-pwCVQZ levels shows that, when going from furazan to 3,4-dinitrofurazan, the presence of the electron-withdrawing NO2 group decreases the bond lengths and increases the C–C=N bond angles of the furazan ring. According to ICSSZZ aromaticity descriptors, the aromaticity of furoxan and 3,4-dinitrofurazan is lower than that of furazan. This is in agreement with the calculated ring current densities induced by an external magnetic field.

Nitroxy- and azidomethyl azofurazans as advanced energetic materials

Progress in the rocket industry is only possible on the basis of new, higher performance and more environmentally friendly materials compared to up-to-date propellant ingredients for liquid, solid, gelled and hybrid propellant systems. In this work, synthetic methods have been developed for the preparation of new energetic azofurazans bearing nitroxymethyl or azidomethyl groups. All prepared compounds were fully characterized by multinuclear NMR and IR spectroscopies, as well as elemental analyses. An analysis of the structural features based on the X-ray single-crystal diffraction made it possible to discuss their influence on the densities of the azofurazans of this study. Thermal decomposition and combustion of nitroxymethyl and azidomethyl azofurazans were studied using a number of complementary experimental techniques, namely thermogravimetry, differential scanning calorimetry, manometry, microthermocouple measurements in the combustion wave. The structural and physical characteristics of these new energetic analogues illustrate the extent to which the nature of the explosophoric groups can be used to tune the performace of the azofurazan framework. These azofurazans possess positive calculated enthalpy of formation and are promising candidates for new environmentally friendly energetic materials.

Conversion of Bacterial Cellulose to Cellulose Nitrate with High Nitrogen Content as Propellant Ingredient

Cellulose nitrate has attracted great interest amongst researchers due to its uses in wide range of products including paint and gun propellant. Therefore, this work focuses on the synthesis of cellulose nitrate from two different sources of cellulose; plant and bacterial, in order to obtain high percentage of nitrogen content hence suitable for propellant application. The synthesis of cellulose nitrate was carried out via nitration method using nata de coco and kapok (Ceiba pentadra L) as a raw materials of cellulose. The samples were then characterized by elemental analysis, fourier transform infrared (FTIR) spectroscopy, x-ray diffraction and surface electron morphology (SEM). FTIR analysis showed the presence of NO2 groups in both nitrocellulose proving that nitrocellulose was successfully synthesized by nitration method even though it was produced from different sources of cellulose. It is also showed nitrocellulose with high percentage of nitrogen content was obtained from bacterial cellulose, 12.69% rather than plant cellulose.

Crystal Characterization of Anionic Salt Compounds as Composite of Solid Propellant Oxidizing Agent

Composite solid propellants are preferred for use in defense and space applications because of their high energy density and simplicity. Oxidizers take up the highest percentage in propellant ingredient. KNO3, KClO4 and K2Cr2O7 are among the inorganic oxidizers with similar cation for present study, and their chemical and physical properties are fully understood. However, the relationship between thermal stability and electrostatic potential energy based on structural analysis has not yet been studied. In this study we used high resolution XRD data to study the electrostatic potential energy of the KNO3, KClO4 and K2Cr2O7 crystal structures.

Mechanical Properties and Thermal Decomposition Behaviors of Hydroxyl‐Terminated Polybutadiene/Glycerol Propoxylate Blend and Its Application to Ammonium Nitrate‐Based Propellants

AbstractHydroxyl‐terminated polybutadiene (HTPB) is commonly used as a binder ingredient in composite propellants. In this study, a plasticizer was added to the binder to promote its plasticity and flexibility. Glycerol propoxylate (GPO) is a triol material with a zigzag structure, and it has one oxygen atom in a repeating unit. GPO would be a good plasticizer for HTPB binder to obtain good elasticity; furthermore, it would be suitable for improving the burning characteristics of the HTPB propellant. The addition of GPO to the HTPB binder was effective in extending the pot life and improving the mechanical properties of the propellant. The thermal decomposition behaviors of the HTPB/GPO blends were almost the same as that of the HTPB binder, except that the beginning consumption temperature of the blends was lower than that of HTPB. The ignitability at low pressure for the ammonium nitrate‐based propellant was improved by using the HTPB/GPO binder, whereas GPO did not enhance the burning rate of the propellant.

Theoretical evaluation of TKX‐50 as an ingredient in rocket propellants

AbstractDihydroxylammonium‐5,5′‐bistetrazolyl‐1,1′‐diolate (TKX‐50), is one of the most promising energetic materials that has been reported in recent time. TKX‐50 shows great potential for future application as a secondary explosive, due to its sensitivity and explosive performance data. In this work, we report initial computational results which have been undertaken to investigate the viability of the application of TKX‐50 as an energetic ingredient in rocket propellants.

Studies on Aluminum Agglomeration and Combustion in Catalyzed Composite Propellants

Composite propellants are tested using the quench particle collection bomb (QPCB) for the pressure ranging from 2 to 8 MPa to estimate the particle size distribution of aluminum agglomerates from quenched combustion residues emerged out from the burning surface. The major ingredients included in the propellants are ammonium perchlorate (AP), aluminum (Al), hydroxyl-terminated polybutadiene (HTPB), and toluene diisocyanate (TDI). Five propellant compositions are considered in this study; two of them are mixed with catalysts. Propellant formulation variables like the coarse AP/fine AP ratio, total solid loading, catalyst percentage, and aluminum content are varied to assess their effects on the aluminum agglomeration process at different pressures. Unburnt aluminum in agglomerates is continuously getting combusted as they move out from the propellant burning surface. Large agglomerates comprise both Al2O3 and unburnt aluminum. The majority of agglomerates are spherical in shape, and the sizes vary from 31 to 115 $$\mu$$ m for non-catalyzed propellants and from 28 to 136 $$\mu$$ m for catalyzed propellants over the tested pressure conditions. These results can give further insight into the aluminum agglomeration process of catalyzed and non-catalyzed propellants and also affect the choice of the propellant ingredient percentage aimed at reducing aluminum agglomeration, which causes two-phase flow losses of thrust and slag accumulation in full-scale solid rocket motors.

Laboratory Scale Slow Cook-Off Testing of Rocket Propellants: The Combustion Rate Analysis of a Slowly Heated Propellant (CRASH-P) Test.

Solid rocket propellants are widely used for propulsion applications by military and space agencies. Although highly effective, they can be dangerous to personnel and equipment under certain conditions, with slow heating in confined conditions being a particular danger. This paper describes a more affordable laboratory test that is easier to set up and was developed for screening rocket propellant ingredients. Rocket propellants are cast into sample holders that have been designed to have the same confinement as standard rocket motors (propellant volume to total volume in the container) and ensure that the propellant is not easily vented. Reaction violence is quantified by the time it takes to reach 90% of the maximum pressure after autoignition, which is analogous to blast overpressure gauges used to measure violence in a full-scale test. A positive correlation was observed between the speed and pressure produced from the reaction and the power produced by the rocket propellant during the reaction.

Laboratory Scale Slow Cook-Off Testing of Rocket Propellants: The Combustion Rate Analysis of a Slowly Heated Propellant (CRASH-P) Test

Solid rocket propellants are widely used for propulsion applications by military and space agencies. Although highly effective, they can be dangerous to personnel and equipment under certain conditions, with slow heating in confined conditions being a particular danger. This paper describes a more affordable laboratory test that is easier to set up and was developed for screening rocket propellant ingredients. Rocket propellants are cast into sample holders that have been designed to have the same confinement as standard rocket motors (propellant volume to total volume in the container) and ensure that the propellant is not easily vented. Reaction violence is quantified by the time it takes to reach 90% of the maximum pressure after autoignition, which is analogous to blast overpressure gauges used to measure violence in a full-scale test. A positive correlation was observed between the speed and pressure produced from the reaction and the power produced by the rocket propellant during the reaction.

Bridged and fused triazolic energetic frameworks with an azo building block towards thermally stable and applicable propellant ingredients

Smart assembly of an azo bridge into trinitromethyl triazoles, and controllable azo-trinitromethyl cyclization yield a novel green high-density energetic oxidizer and two fused nitrotriazolones with excellent thermal stabilities.

Guanidinium 5,5'-Azotetrazolate: A Colorful Chameleon for Halogen-Free Smoke Signals.

A progressive halogen‐free multicolored smoke system to obtain white, red, violet, yellow, green, and blue smoke color is presented. The nitrogen‐rich salt guanidinium 5,5′‐azotetrazolate (GZT), which is usually applied as a gas generator or propellant ingredient, was combined with different smoke dyes (Solvent Red 1, Solvent Violet 47, Solvent Green 3, Solvent Yellow 33). These two‐component smoke mixtures offer a convenient and safe multicolor approach without the need for potassium chlorate or any other hazardous material. The common smoke characteristics with respect to burn time/burn rate, yield factor, transfer rate, as well as energetic properties were determined and compared with classic chlorate‐based formulations currently used. To the best of our knowledge, nothing comparable is known in the literature and a completely new research area in modern pyrotechnics is opened.

A Theoretical Method to Compare Relative Bulk Thermal Sensitivities of Several Common High Explosives

AbstractSimultaneous numerical solutions of the second and first order partial differential equations describing the first order decomposition of seven explosives are presented. The solutions were used to compare the critical rates of heat production per unit mass of each material. The lower such a rate is the more sensitive is the explosive. The relative sensitivities of Tetryl, PETN, RDX, TNT, HMX and TATB are as might have been predicted. However, PBX9404 shows apparently enhanced thermal sensitivity compared with these six explosives. This provides a warning that some modern low vulnerability composite explosives based partly on propellant ingredients might constitute enhanced thermal threats.