Phase Stabilized Ammonium Nitrate Research Articles

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

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

Traditional vs. Energetic and Perchlorate vs. "Green": A Comparative Study of the Choice of Binders and Oxidising Agents.

The aim of this article is to compare rocket propellants containing a traditional binder (hydroxyl-terminated polybutadiene) and an energetic binder (glycidyl azide polymer), as well as a perchlorate oxidising agent and a "green" one, i.e., ammonium perchlorate and phase-stabilised ammonium nitrate. We have outlined the effects of individual substances on the sensitivity parameters and decomposition temperature of the produced solid propellants. The linear combustion velocity was determined using electrical methods. Heats of combustion for the propellant samples and the thermal decomposition features of the utilised binders were investigated via differential scanning calorimetry (DSC). Activation energy values for the energetic decomposition of the propellants were determined via the Kissinger method, based on DSC measurements at varied heating rates.

Mechanical Compression Behaviour of "Green" Rocket Propellants

The issues related to mechanical resistance of solid rocket propellants, which can appear during storage or handling of the launching system, are considered to directly influence the burning performance. Thus, in this study, four new types of composite rocket propellants, based on an environmentally friendly oxidizer (phase-stabilized ammonium nitrate), a metallic fuel (aluminium), and a "green" polyurethane-based binder (synthesized from an oligomeric isocyanate and a blend of polyester-polyols obtained through the catalytic degradation of polyethylene terephthalate), were subjected to compression mechanical analysis in order to highlight the importance of the binder on the response given by the tested materials subjected to compressive loads. The samples showed remarkable mechanical performances, the experiments allowing us also to determine the influence of the binder composition and fuel granulation on mechanical properties of the composite propellant.

The Influence of Potassium Salts Phase Stabilizers and Binder Matrix on the Properties of Novel Composite Rocket Propellants Based on Ammonium Nitrate.

The environmental impact and availability of ingredients are vital for the new generation of rocket propellants. In this context, several novel composite propellants were prepared based on the "greener" oxidizer phase-stabilized ammonium nitrate (PSAN), a micronized aluminum-magnesium alloy fuel, iron oxide powder burn rate modifier, triethylene glycol dinitrate (TEGDN) energetic plasticizer and a polyurethane (PU) binder. The novelty of this study is brought by the innovative procedure of synthesizing and combining the constituents of these heterogeneous compositions to obtain high-performance "eco-friendly" rocket propellants. The polymorphism shortcomings brought by ammonium nitrate in these energetic formulations have been solved by its co-crystallization with potassium salts (potassium nitrate, potassium chromate, potassium dichromate, potassium sulphate, potassium chlorate and potassium perchlorate). Polyester-polyol blends, resulting from recycled post-consumer polyethylene terephthalate (PET) glycolysis, were utilized for the synthesis of the polyurethane binder, especially designed for this type of application. To adjust the energetic output and tailor the mechanical properties of the propellant, the energetic plasticizer TEGDN was also involved. The performance and safety characteristics of the novel composites were evaluated through various analytical techniques (TGA, DTA, XRD) and specific tests (rate of combustion, heat of combustion, specific volume, chemical stability, sensitivity to thermal, impact and friction stimuli), according to NATO standards, providing promising preliminary results for further ballistics investigations.

Performance and Sensitivity Properties of Solid Heterogeneous Rocket Propellant Based on a Binary System of Oxidizers (PSAN and AP)

Solid heterogeneous rocket propellants (SHRP) containing ammonium perchlorate (AP) emit a lot of hydrogen chloride (HCl) during combustion, which poses various environmental issues and makes the detection of the rockets easier. Part of the AP can be replaced by ammonium nitrate (V) (AN), which does not lead to the production of HCl. AN is a commonly used environmentally friendly oxidizer, but it is not usually applied in SHRP due to its disadvantages. One of these disadvantages is a phase transition near room temperature, which causes the density change of AN. Three types of phase stabilized ammonium nitrate (V) (PSAN) with inorganic potassium salts were obtained in order to shift this transition into higher temperatures (above the temperature range of the storage and the usage of SHRP). The SHRP with the PSAN were obtained, and the measurements of the heat of combustion, density, hardness, the sensitivity to mechanical stimuli and the thermomechanical properties were performed. The obtained propellants were characterized by similar operational parameters or were slightly lower than those without the PSAN. This means that AP can be partially replaced without significantly compromising the handling, safety or functionality of the propellants, while increasing the environmental performance of the solution.

Novel Polyurethanes Based on Recycled Polyethylene Terephthalate: Synthesis, Characterization, and Formulation of Binders for Environmentally Responsible Rocket Propellants.

Novel polyurethane-based binders, specifically designed for environmentally responsible rocket propellant composites, were obtained by employing the polyester-polyols that resulted from the degradation of polyethylene terephthalate waste. A new class of “greener” rocket propellants, comprising polyurethanes (based on recycled PET) as the binder, phase stabilized ammonium nitrate (PSAN) as the eco-friendly oxidizer, and triethylene glycol dinitrate (TEGDN) as the energetic plasticizer, together with aluminum as fuel and Fe2O3 as the catalyst, is herein reported. The components of the energetic mixtures were investigated (individually and as composite materials) through specific analytical tools: 1H-NMR, FT-IR, SEM-EDX, DTA and TGA, tensile and compression tests, DMA, and micro-CT. Moreover, the feasibility of this innovative solution is sustained by the ballistic performances exhibited by these composite materials in a subscale rocket motor, proving that these new formulations are suitable for rocket propellant applications.

High‐Precision Density Measurements of Energetic Materials for Quality Assessment

AbstractEven though helium pycnometry is considered a very precise method of density determination, its use to analyse factors influencing crystal quality (e. g. solvent inclusions, amorphous states, crystal defects…) is limited due to the unknown inherent accuracy of the method. Previous studies have attempted to identify the best possible accuracy of helium pycnometry. However, no robust method has been proposed to validate even the precision obtained. This means that the often occurring, seemingly random density deviations have never been satisfactorily explained. In this study the influencing factors on density measurements of the CL‐20/HMX cocrystal and phase stabilised ammonium nitrate carried out with an AccuPyc 1340 TEC were quantified and a robust method of data analysis was developed to judge with certainty the quality and significance of the data obtained. This study shows that statistical tests such as the t‐test and ANOVA cannot be utilised to differentiate between samples or repeat measurements, even though the density data points exhibit a normal distribution. By utilising confidence intervals and quantifying the three major sources of error (sampling error, change in barometric pressure during the measurement, and weight in error), a repeatability of 0.015 % was achieved and a method was developed that enables differentiation between samples with a certainty as good as 0.05 %.

Advances in phase stabilization techniques of AN using KDN and other chemical compounds for preparing green oxidizers

Abstract Research and development of green oxidizers and green fuels as a possible replacement for ammonium perchlorate (NH4ClO4, AP) and hydrazine (N2H4) respectively has been increased considerably in the recent years. AP and hydrazine are the oxidizer and fuel entities, and used in solid and liquid rocket motors respectively. AP is highly toxic and led to adverse health effects, while hydrazine is carcinogenic in nature. AP is in use from the last several decades for rocket and space shuttle propulsion, while hydrazine is used in upper stage liquid propelled rocket motors. It's a tough task to replace AP with the currently available green oxidizers; since their ballistic properties are weaker when compared to AP and also they can't be successfully deployed in a solid rocket motor at present. Some important available solid green oxidizers are ammonium nitrate (AN), ammonium dinitramide (ADN), hydroxyl ammonium nitrate (HAN), and hydrazinium nitroformate (HNF). However, AN is one of the cheap and readily available oxidizer, and has great potential to use in solid/ liquid rocket motors. Tremendous progress has been envisaged till now, and more progress will be there in the coming future over the development of AN based green energetic materials (GEM's). A concise overview has been presented over the development of phase stabilized ammonium nitrate (PSAN) and AN/KDN based green oxidizers in the present review paper.

Effect of catalysts on the burning rate of phase stabilized ammonium nitrate based composite propellants

The Ammonium Nitrate based composite propellants are widely used in the applications of tactical missiles and explosives due to its least toxicity and smokeless combustion. The main disadvantage of ammonium nitrate based propellants is its poor burning rate. Hence, it is required to enhance its burning rate for attaining a better performance. One of the several methods of upgrade the burning rate of composite solid propellants is the addition of catalysts to the propellant. The present study aims to investigate the effect of addition of transition metal oxides as the catalysts to the phase-stabilized ammonium nitrate based composite solid propellants and to study its thermal decomposition characteristics.

A novel hot aerosol extinguishing agent with high efficiency for Class B fires

SummaryA novel hot aerosol extinguishing agent (HAEA), which is the combination of pyrotechnics and flame retardant technology, was found to have great efficiency in extinguishing Class B fires. A mixture of P and P3N5, referred to as P90x, was chosen as the reductant, and phase stabilized ammonium nitrate was chosen as the oxidant. This paper describes a study of the effectiveness of this agent in extinguishing n‐heptane fires (ie, Class B fires). We determined that the best efficiency was 15 g/m3 for extinguishing n‐heptane fires, four times more efficient than a traditional agent. The efficiency increases as the mass fraction of P90x rises. We also identified the key difference between the novel extinguishing agent and the traditional agent. The former consists of an inorganic phosphorus compound, while the latter is mainly comprised of KOH. Consequently, their extinguishing mechanisms are different. The phosphorus oxide of the novel HAEAs is the leading component to extinguish fire, which is more effective than alkali salts.

Mixtures of Phase-stabilized Ammonium Nitrate and Tetrazoles as New Gas-generating Agent Compositions

Mixtures of Phase-stabilized Ammonium Nitrate and Tetrazoles as New Gas-generating Agent Compositions

EFFECT OF CU-CO MIXED METAL OXIDES ON THE COMBUSTION OF PSAN-HTPB BASED SOLID PROPELLANTS

Composite propellants based on ammonium perchlorate (AP) as oxidizer are state-of-the-art. However, global environmental impact restricts AP-based propellants because of their high chlorine exhaust. Therefore, efforts are on to innovate propellants with clean exhaust. Ammonium nitrate (AN) has, thus, regained importance in the field of propellants and explosives, more specifically in insensitive formulations, because of its clean burning and low hazard. However, the stumbling block for the application of AN - as solid propellant oxidizer has been its dimensional instability caused by phase transformation which results in increase of volume and porosity of the propellant grain. This can be overcome by the use of phase stabilized ammonium nitrate (PSAN). In the present study AN phase stabilized by incorporating 10% KN to prepare composite solid propellant. Copper-Cobalt mixed metal oxides have been synthesized via citric acid complexing method. Three different catalysts were prepared with different Cu-Co molar ratios 1, 0.5 And 2 in the initial reactants. The synthesized catalysts were then added to the PSANHTPB(Phase Stabilized Ammonium Nitrate- Hydroxyl Terminated Poly-Butadiene) composite formulations. These propellant samples were subjected to burn rate measurement in a Crawford High Pressure Strand Burner and thermal degradation studies in Simultaneous Thermal Analyzer (STA). The thermal decomposition and burn rate of the propellant is observed maximum on the addition of Copper-Cobalt mixed metal oxide catalyst with molar ratio 2. A total of six propellant samples catalyzed and noncatalyzed and one preheated virgin sample were undertaken for the above analysis and results obtained are discussed. It has been observed that except the propellant sample with Cu-Co-III and virgin propellant where PSAN was prepared by solid mixing, other propellant samples were hard to burn.

Thermal behavior of glassy phase stabilized ammonium nitrate (PSAN) thin films

Ammonium nitrate (AN) is a high interest material because of its wide usage in propellants and explosives but can be difficult to handle from a formulation standpoint. It is soluble in many common solvents and has complex phase behavior. Here, we formulate phase stabilized AN (PSAN) films in a polymer matrix and characterize thermal and phase behavior using neutron reflectometry and ellipsometry. These techniques are highly sensitive to small changes in composition and density which occur during phase transitions. Our PSAN films are generally stable up to 160°C, though we observe small material loss between 60 and 100°C, which we attribute to solvent interactions with the PSAN. Crystallization of AN from supersaturated polymer is most common at thicker regions of the film, suggesting a critical nucleation thickness for the AN which can be avoided by making very thin films.

Differential scanning calorimetry analysis of crystal structure transformation in spray-dried particles consisting of ammonium nitrate, potassium nitrate, and a polymer

Ammonium nitrate (AN) is an affordable oxidant; however, it undergoes crystal structure transformations accompanied by a change in volume at comparatively low temperatures (approx. 30, 80, and 125 °C) and exhibits high hygroscopicity. Both these properties are particularly problematic for the industrial application of AN. In a previous study, we prepared spray-dried particles comprising three components: AN, potassium nitrate (PN) as a phase stabilizer, and a polymer (e.g., polyvinyl alcohol, carboxymethylcellulose salt, and styrene-butadiene latex), which was confirmed to provide effective moisture proofing. In the present study, the crystal transformation behavior of AN/PN/Polymer particles is investigated by observing their thermal behavior by differential scanning calorimetry. The results reveal that phase-stabilized AN can be successfully prepared by the addition of PN. In addition, an intriguing possibility was identified in that carboxymethylcellulose ammonium salt and polyvinyl alcohol, which were both added as polymer components for moisture proofing, also acted as phase stabilizers for AN crystal transformation.

A Burning Rate Equation as a Function of Pressure and Temperature for a BTA · NH3/PSAN Mixture

The burning rate of propellants is affected by pressure and temperature. The relation between the burning rate and pressure has been well studied. However, the effect of the initial temperature on the burning rate has not been investigated quantitatively. In this study, the burning rate of bis (1H-tetrazolyl) amine ammonium salt and potassium nitrate phase-stabilized ammonium nitrate mixtures was examined and an equation for the burning rate as a function of pressure and temperature was obtained. In general, the burning rates predicted by the regression equations were in good agreement with the observed values. The temperature sensitivities were also predicted using the regression equation and compared with the observed values and good agreement was found between the predicted and observed values.

Combustion Behavior of Solid Oxidizer/Gaseous Fuel Diffusion Flames

The diffusion flame combustion behavior of several solid oxidizers (ammonium nitrate, phase-stabilized ammonium nitrate, ammonium perchlorate, and ammonium dinitramide) in combination with a hydrocarbon fuel (ethylene) was examined. The oxidizers were first analyzed by differential scanning calorimetry, thermal gravimetric analysis, and evolved gas analysis to gain an understanding of their basic decomposition characteristics. Next, an opposed flow burner was used to establish a diffusion flame between the decomposition products of the oxidizer(s) and the fuel. Regression rates of the solid oxidizer were measured by a linear variable displacement transducer as a function of fuel flow rate. Ammonium dinitramide demonstrated the highest linear regression rate characteristics by up to two orders of magnitude, followed by ammonium perchlorate, phase-stabilized ammonium nitrate, and finally ammonium nitrate. When comparing mass burning rates, ammonium perchlorate compares favorably to solid fuels such as hydroxyl-terminated polybutadiene. In addition, the flame zone(s) were imaged via high-speed photography to provide detailed information of flame characteristics. Flame imaging revealed large melt layers and boiling type behavior for ammonium nitrate and phase-stabilized ammonium nitrate as well as droplet ejection from the melt layer. The goal of this study was to gain an understanding of the fundamental combustion behavior of a diffusion flame between a solid oxidizer and a hydrocarbon fuel as a stepping-stone to more complex systems such as reverse hybrid rockets.

Experimental correction of combustion gas properties of AN-based composite solid propellants used for turbo-pump starter

Solid propellant gas generators play a role as a turbo-pump starter in liquid propellant propulsion systems by supplying pressurized gas to power turbines for engine start. Among the required combustion gas properties provided by solid propellant gas generators, the combustion gas temperature should not exceed a certain temperature which may damage the turbine blades. For such purposes, phase stabilized ammonium nitrate (AN)-based propellants have been widely used with a low combustion temperature. However, gas generator propellants with ammonium nitrate have historically exhibited incomplete combustion resulting in increased flame temperatures differing significantly from equilibrium values. In consideration of design requirements, an engineering model of solid propellant gas generator was manufactured using the combustion gas properties calculated by a chemical equilibrium code and then hot-fire tests were performed. Procedures for the correction of T 0 , k and M w of the combustion gas from the experimental results are introduced and the following effects on the design of the solid propellant gas generator are presented. From the experimental correction of the combustion gas properties, it is found that the amount of the propellant could be reduced while providing the same amount of available power to the turbines and consequently, the size of the gas generator could also be decreased.

Effect of carbon nanotube on the thermal decomposition characteristics of selected propellant binders and oxidisers

The effect of carbon nanotube (CNT) on the thermal decomposition behaviour of polymeric binders viz., hydroxyl terminated polybutadiene (HTPB) and glycidyl azide polymer (GAP) as well as oxidisers namely ammonium perchlorate (AP) and phase stabilised ammonium nitrate (PSAN) was investigated using simultaneous TG–DSC. The results indicate that addition of CNT to AP, lowered the thermal decomposition of AP but CNT addition to HTPB, increased the thermal stability of HTPB. The thermal decomposition characteristics of PSAN and GAP were not influenced by CNT. Ignition delay studies were carried out in a tube furnace using HTPB–AP propellant systems. CNT reduced the ignition delay of a propellant based on HTPB with AP oxidiser. The observed phenomena were explained based on the likely reaction of CNT with the compounds formed at high reaction temperatures.

COMBUSTION AND IGNITION PROPERTIES OF AMMONIUM NITRATE AND ACTIVATED CARBON MIXTURES

In order to obtain a better understanding of combustion and ignition properties of ammonium nitrate (AN) and activated carbon (AC) mixtures, friction test, thermal analysis, and 200-mL closed vessel combustion test were carried out and the influence of the mixing ratio on the combustion and ignition properties of various compositions of AN/AC mixtures was investigated. As a result of the BAM friction sensitivity test, all mixtures showed negative results. From differential scanning calorimetry (DSC) test results, each AN mixed with more than 4 wt% of AC mixtures showed violent exotherm after the melting of AN and some of the mixtures exploded in a SUS crucible. The largest heat of reaction was observed at a higher concentration than the stoichiometric composition. The results of 200-mL closed vessel test showed that the powdered AN and the phase stabilized AN (PSAN) mixed with AC showed a fast reaction and a high pressure due to the large amount of gas release and the maximum pressure, and the maximum rate of pressure rise showed the maximum values at a higher concentration than the stoichiometric composition.

Phase stabilization of ammonium nitrate with binary additives consisting of potassium nitrate and complexone salts

The paper deals with the search for and optimization of a method for preparing phase-stabilized ammonium nitrate as oxidant for solid propellants with environmentally friendly combustion products. The effect exerted on the energy of the V → IV and IV → III polymorphous transitions of ammonium nitrate by the total content of the binary additive potassium nitrate-disodium tetrahydrogen nitrilotris-(methylenephosphonate), component ratio, and temperature and time of the cocrystallizate treatment was examined.