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1

Evaluation of Potassium Perchlorate as a Burning Rate Modifier in Composite Propellant Formulations

Jain S., Mehilal D., Singh P. P., Bhattacharya B.

Central European Journal of Energetic Materials

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2016

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Vol. 13, no. 1

231--245

EN

The burning rate of a solid composite propellant is one of its most important ballistic properties. To achieve a specified burning rate, transition metal oxides are used as burning rate modifiers. However, addition of transition metal oxides creates inertness in the composition. To avoid such inertness, an attempt has been made to incorporate potassium perchlorate (KP) as a burning rate modifier by partially replacing ammonium perchlorate (AP), up to the 10% level, and the composition was then studied in detail for its mechanical, thermal and ballistic properties. The data revealed that no change occurred in the case of the mechanical properties, however, the thermal stability decreased as the KP content was increased. The burning rate data revealed that on incorporation of 10% KP, there was an enhancement in the burning rate of up to 35% in comparison to the original composite propellant formulation, but beyond this no enhancement in burning rate was observed, indicating that the optimum content for KP in the composition had been reached.

2

A Validated Reverse Phase HPLC Technique for the Determination of TATB Assay

Bhattacharyya S. C., Patil R. S., Santosh M. S. S. N. M., Bhattacharya B., Malik R. K., Mehra A.

Central European Journal of Energetic Materials

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2016

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Vol. 13, no. 3

641--657

EN

The main hurdle for the estimation of the purity of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is its insolubility in most of the known organic solvents. In the conventional method, TATB is digested with steam in a modified Kjeldahl digester and the ammonia evolved is estimated quantitatively. To do away with this cumbersome method, a simple, rapid HPLC technique using a reverse phase C-18 column has been established for quantitative determination of the purity of TATB. A sharp and symmetrical peak with a retention time of 2.92 min at 355 nm is obtained for pure TATB when the flow rate is 2.0 mL/min. The linearity of the detector response has been studied with sample concentrations ranging from 10 to 50 mg/L. The method addresses two important issues of sample preparation and the precision of measurement. Unlike the previously reported HPLC techniques which mainly aimed at the detection of TATB, the present work is a validated account of a quantitative estimation of purity. Regular production batch samples have been assayed by this method and the results are compared with those obtained from the conventional analysis. The HPLC method is convenient and reliable for quality control of the product at the plant level.

3

Various Methods for the Determination of the Burning Rates of Solid Propellants : an Overview

Gupta G., Jawale L., Mehilal D., Bhattacharya B.

Central European Journal of Energetic Materials

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2015

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Vol. 12, no. 3

593--620

EN

The burning rate of propellants plays a vital role among the parameters controlling the operation of solid rocket motors, therefore, it is crucial to precisely measure the burning rate in the successful design of a solid rocket motor. In the present review, a brief description of the methods for the determination of the burning rate of solid rocket propellants is presented. The effects of various parameters on the burning rate of solid propellants are discussed and reviewed. This review also assesses the merits and limitations of the existing different methods for the evaluation of the burning rate of solid rocket propellants.

4

Application of Twin Screw Extrusion for Continuous Processing of Energetic Materials

Dombe G., Mehilal D., Bhongale C., Singh P. P., Bhattacharya B.

Central European Journal of Energetic Materials

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2015

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Vol. 12, no. 3

507--522

EN

Continuous processing of energetic materials using a twin screw extruder is gaining importance as it is a safe and cost-effective alternative to conventional batch processing. The continuous process based on a twin screw extruder combines the capabilities of intensive mixing and high pressure extrusion. It is used for processing a variety of energetic materials, such as gun and rocket propellants, plastic bonded explosives, pyrotechnics, thermo-baric explosives, etc. The twin screw extruder process demands various safety features for the processing of energetic materials. Therefore, exhaustive characterisation of the energetic materials in terms of safety and rheology, coupled with characterisation of the mechanical components of the extruder, are essential for designing a safe continuous process. In this article, a technological overview of continuous processing for energetic materials is presented, along with its various features, process design methodology and safety issues.

5

Process Optimization for the Gas-Liquid Heterogeneous Reactive Crystallization Process Involved in the Preparation of the Insensitive High Explosive TATB

Nandi A. K., Kshirsagar A. S., Thanigaivelan U., Bhattacharyya S. C., Mandal A. K., Pandey R. K., Bhattacharya B.

Central European Journal of Energetic Materials

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2014

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Vol. 11, no. 1

31--57

EN

The thermally stable, insensitive, high explosive 1,3,5-triamino-2,4,6- trinitrobenzene (TATB) is manufactured by amination of 1,3,5-trichloro-2,4,6- trinitrobenzene (TCTNB) in toluene with NH3 gas. It is an isothermal, single-feed, semi-batch, gas-liquid heterogeneous, reaction crystallization process. The amination process is discussed by applying the chemical engineering methodology of mass transfer and reactive crystallization processes based on Two-Film Mass- Transfer (TFMT) theory. Kinetic expressions have been developed to define the chemical reactions as well as the physical phenomena (mass transfer) associated with this process. A single expression has been derived to explain the dependence of the ammonia consumption rate on various process parameters. Subsequently, the influence of various process parameters on the product quality (particle size and chloride impurity content) has been studied on the laboratory scale. Finally, the process has been established in the pilot plant, with optimized process conditions, to realize TATB of desired particle size and chloride content. The effects of feeding excess ammonia, and the presence of mercaptans/hydrogen sulphide impurities in poor quality toluene on the formation of certain undesirable by-products in TATB, are also discussed.

6

Optimization of Ammonium Sulfamate Nitration for the Preparation of Ammonium Dinitramide

Mandal A. K., Kunjir G. M., Singh J., Adhav S. S., Singh S. K., Pandey R. K., Bhattacharya B., Lakshmi Kantam M.

Central European Journal of Energetic Materials

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2014

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Vol. 11, no. 1

83--97

EN

The reaction kinetics for the preparation of ammonium dinitramide (ADN) is described. ADN is the ammonium salt of the dinitramide anion, and belongs to the group of inorganic oxidizers, mainly useful for energetic rocket propellant formulations, particularly for underwater applications. It is also a potential candidate to replace ammonium perchlorate (AP), in order to develop chlorine-free, green propellants. At HEMRL, ADN is prepared by the nitration of ammonium sulfamate (AS) using mixed acid, followed by hydrolysis, neutralization with ammonia (g) and rectification using solvent. The nitration of ammonium sulfamate (AS) is carried out at a subzero temperature of -40 ±1 °C. The yield of ADN is reliant on the formation of dinitramidic acid, an intermediate product formed during the hydrolysis step, and its stability is predominantly dependent upon the level of acidity and temperature of the reaction medium. Prior to these kinetics studies, process optimization of the nitration of ammonium sulfamate (AS) was performed and gave the final mole ratio of AS:HNO3:H2SO4. Since the nitration of AS is sensitive to temperature, the rate of reaction was studied at fixed temperatures with variation of time, keeping all of the other parameters, such as vessel volume, agitator speed, feed rate etc., constant. During these studies, predetermined quantities of ammonium sulfamate (AS) and mixed acid were allowed to react at a fixed temperature (-40 ±1 °C) for different reaction periods to generate the concentration profile of AS. Using this concentration profile, the reaction order and reaction rate constant were evaluated. In order to find the effect of temperature on the reaction rate and yield, experiments were conducted at other temperatures such as -30 and -50 °C. In the present studies, it was found that the optimum temperature of nitration is -40 ±1 °C and that the rate of reaction follows a pseudo second order process with rate constant 0.01113 (min-1)•(mol/L)-1. The reaction time evaluated for 55 to 60% conversion is about 70-80 minutes at -40 ±1 °C, based on this kinetics. The activation energy of AS nitration was found to be -4.6 kcal/mol, using the reaction kinetic data based on the temperature dependent rate equation derived from Arrhenius’s law.

7

Studies on High Burning Rate Composite Propellant Formulations using TATB as Pressure Index Suppressant

Mehilal, Jawalkar S., Kurva R., Sundaramoorthy N., Dombe G., Singh P. P., Bhattacharya B.

Central European Journal of Energetic Materials

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2012

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Vol. 9, nr 3

237-249

EN

High burning rate propellant compositions are generally used in gas generators to eject missile from canister. Because of high burning rate, pressure index of the composition increases during burning. To reduce the pressure index, a high burning rate composite propellant formulations (~20 mm/s) based on AP/HTPB/Al have been prepared by incorporating TATB and studied in detail for viscosity build-up, thermal and mechanical properties, sensitivity as well as burning rate and pressure index (n). The data indicate that there is a decrease in end of mix viscosity on increasing the percentage of TATB. The same trend was also observed with mechanical properties while significant improvement in overall thermal stability was clearly observed. The sensitivity data indicate that impact and friction values show decreasing trend infer better safe to handle. The burn rate data reveal that on addition of TATB from 0.5 to 2% decrease in burning rate was not observed while on addition of further TATB up to 5% and beyond this significant decrease in burning rate was observed. The data on pressure index (n) also reveal that TATB is very effective in reducing the 'n' value up to 2% and beyond this 'n' value increases close to standard composition. The data on 'n' value reveal that it reduces from 0.47 to that of standard composition to 0.36 for the compositions containing TATB up to 2.0% in the pressure range of 60-90 kg/cm2.

8

Development of a Composite Propellant Formulation with a High Performance Index Using a Pressure Casting Technique

Ramesh K., Jawalkar S. N., Sachdeva S., Bhattacharya B.

Central European Journal of Energetic Materials

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2012

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Vol. 9, nr 1

49-58

EN

There is a continuous demand for high performance composite propellant formulations to meet future requirements. The performance of composite propellant formulations can be enhanced by the addition of energetic oxidizers, like ADN/HNF as well as an energetic binder & a plasticizer. However, on incorporation of energetic ingredients, the composition becomes sensitive, and thus processing, handling and transportation pose a greater threat. Therefore, a moderately high burn rate composition having a burn rate ~ 13-14 mmźs -1 at 7000 kPa was tailored by increasing the solid loading of the propellant from 85.15% to 87.27% with the help of ammonium perchlorate and process aids without affecting the burn rate and mechanical properties. The tailored composition was studied for different properties such as end of mix viscosity, density, mechanical & ballistic properties. The evaluated data reveal that the end of mix viscosity of the tailored composition is higher than the base composition, i.e., 672 Paźs and 2340 Paźs at the same temperature; however, this viscosity was castable using a pressure casting technique. The properties of the cured propellant reveal that there is an enhancement of density from 1.74 gźcm -3 to 1.79 gźcm -3 with no other changes in mechanical properties. The performance index of the tailored composition has been increased from 416 to 437, well supported by results of ballistic evaluation motors of 2 kg.

9

Seismic resolution over coal seams: a numerical study

Mohanty P., Phadke S., Bhattacharya B.

Acta Geophysica Polonica

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2000

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Vol. 48, nr 2

215-222

EN

Processing tool like migration is rarely applied to high resolution shallow coal seismic data. The improvement of stacked section by using migration is so far only marginal. In addition, it takes tong computing time to perform migration on PC based system commonly used for day-to-day shallow high resolution seismic data processing. With the advent of powerful and inexpensive workstation, migration is carried out on post stack as well as pre stack data. The present study is an example of migration technique applied to zero-offset time sections generated for three different geological models. The geological models incorporate coalseam discontinuities like fault, fold and feeder dyke commonly encountered in the coal bearing formations of eastern India. In order to select a suitable migration scheme, both finite-difference depth migration and frequency wavenumber (f-k) phase shift time-migration are applied to the zero-offset data generated for these models. Depth migration scheme has significantly improved the imaging conditions compared to the f-k phase shift time-migration. Besides, the depth migration restored the lateral continuity of the fault and delineated the small scale structural features clearly in the case of feeder dyke and fold.