Showing papers in "Propellants, Explosives, Pyrotechnics in 1982"

Explosive desensitization studies via chemical group modification. Nitroso-Derivatives of RDX and 3-Amino-TNT

Abstract: With aims toward desensitizing RDX and TNT via molecular modification, mono- and trinitroso-derivatives of RDX and 3-amino-TNT were synthesized and subjected to sensitivity tests. Impact and shock sensitivity data show these compounds to be markedly desensitized. Explosive yield measurements indicate that the changes in power output due to these molecular modifications are minor.

Processing Characteristics of Gun Propellants

Abstract: Using especially modified torque and capillary extrusion rheometers the rheological behaviour of a typical triple-base gun propellant has been examined as a function of such processing variables as temperature, solvent content, time taken to incorporate, filler content and filler shape. Propellant doughs flow according to the law where σ is the shear stress applied to the dough to maintain a shear rate of γ, σ0 is the yield stress at which flow commences, K is the consistency index and n is the flow behaviour index. Variations in these constants as a function of the above mentioned variables are presented and their implications discussed. Resultant changes in the physical properties of the dried extruded propellant also are monitored.

Explosion thermique (cook off) des propergols solides

Abstract: Le document que nous presentons fait le point sur les premiers travaux effectues par le Centre de Recherches du Bouchet de la SNPE, sur les phenomenes d'explosion thermique, destines a etudier la stabilite des propergols solides. Ces travaux nous ont permis de mettre au point une methodologie d'essais pour mesurer assez precisement, les valeurs des constantes cinetiques et physiques des propergols et d'etablir, pour des blocs pleins et cylindriques de propergol composite aluminise, un modele empirique. Ce modele empirique (calque sur le modele theorique de Zinn et Mader(1) qui, experimentalement, ne s'adapte qu'aux explosifs) est susceptible de prevoir, a partir d'un nombre limite d'experiences, les temperatures critiques et les temps d'induction, quelle que soit la taille des blocs de propergol.

Quantum Mechanics and Molecular Dynamics Calculations provide new evidence for a free‐radical shock initiation model

Abstract: The contrast between a hydrodynamic model for shock initiation of explosives and a newer microscopic free-radical model is presented. The primary considerations of the free-radical model are that shock energy is very coherent and that it is strong enough to cause mechanical fracture of covalent bonds. The shock front on a microscopic scale is very narrow (∼5 A to 15 A) and thermal equilibrium does not exist in the front. The free atoms and radicals formed by the shear and acceleration forces in the shock front initiate the chemical reaction that leads to hot spots and the eventual decomposition of the explosive materials. Energy-release rates and vibrational velocities of the covalently bound atoms are factors in establishing detonation velocities. A number of explosives phenomena are discussed as the new model provides explanations for them. New information from molecular dynamics and quantum mechanical calculations on shock waves in condensed systems and recent experimental data are shown to support the free-radical model.

New adducts of octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX)

Abstract: A new series of relatively stable adducts of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) with derivatives of pyridine-N-oxide were prepared. In addition, relative stable new adducts of HMX were prepared with 5-membered, 6-membered, and condensed-ring heterocyclic compounds. Most of the adduct-forming compounds (AFC's) contain an oxygen and/or nitrogen heteroatom, while several contain a sulfur heteroatom. Most of the adducts are equimolar with HMX; however, several contain 2 moles of AFC per mole of HMX and other ratios of AFC:HMX. Some properties of the new adducts are presented.

Thermal Decomposition of RDX Composite Propellants

Abstract: The thermal decomposition characteristics of RDX, binders, and RDX composite propellants were studied using thermal analytical techniques. Three kinds of binders were tested to elucidate the role of binder on the burning rate of the propellants. There were no apparent correlations between the thermal decomposition rates of binders and the burning rates of propellants, whereas there was a correlation between the decomposition temperature and the burning rate of the propellants. It is found that the major factor which controls the burning rate is the initial thermal-decomposition stage of the binders. Thus, the burning rate of nitramine composite propellants appeared to be largely dependent on the physical and chemical properties of binder.

Etude des conditions d'initiation de la pentrite (PETN) par spectrométrie raman ultra‐rapide

Abstract: La diffusion Raman ultra-rapide permet d'etudier les phenomenes tres brefs qui president a la generation de la detonation dans des explosifs secondaires nitres. D'apres une etude theorique precedente, il existe pour ces explosifs une liaison de type RNO2 par ou debute la reaction de decomposition explosive sous choc. Cette etude theorique a ete verifiee experimentalement sur deux de ses conclusions: le changement de phase de la pentrite et les modifications de structure electronique affectant l'une des liaisons ONO2 sous choc. Pour ce faire, une etude de la pentrite a l'etat monocristallin a ete realisee par spectrometrie Raman classique en vue d'une attribution complete du spectre. Il a ete en meme temps observe des eclatements des modes polaires du fait de l'absence de centre d'inversion dans la maille. L'etude experimentale entreprise par la suite a necessite une mise au point du montage Raman avant de conduire aux resultats montrant, outre de faibles deplacements de frequence, d'importantes variations d'intensite de quelques raies pour une certaine pression de choc.

Generation of Free Radicals in RDX and HMX Compositions

Abstract: Efforts to generate detectable concentrations of free radicals in explosives, binders, and their mixtures are described. Radicals were readily produced in polycaprolactone and polyethylene glycol binders at liquid nitrogen temperature using stresses as low as 0.4 kbar. These radicals were all of the peroxy type, and presumably formed by reaction of mechano-radicals with oxygen present in the polymer. No mechano-radicals were observed from HMX or RDX using samples cooled to liquid nitrogen temperature and applied stresses up to 4 kbar. In neither impacted samples that failed to explode nor the residues remaining after a partial explosion were radicals detected by ESR. Low temperature γ-irradiation of these materials was also carried out. Free radical signals originating in both the polymer and the explosive could be identified. The reactivity of NO2 radicals from γ-irradiated HMX is enhanced in the presence of binder. In γ-irradiated HMX/polycaprolactone mixtures, the NO2 radical anneals rapidly at 150 K, versus 240 K for HMX alone. Evidence is presented to suggest that the relatively stable NO2 radical (such as produced by γ-irradiation) in HMX does not play a dominant role in mechanical initiation.

Smoke generators. I. The Ignition of Pyrotechnic White Smoke compositions containing hexachloroethane and silumin by means of an electrically heated coil

Abstract: The ignition by electrically heated coil of two smoke generators containing hexachloroethane and silumin, one of which also contains zinc oxide, has been investigated. The physical conditions of consolidation, that is pressing load (between 7.9 × 106 kg/m2 and 3.1 × 107 kg/m2) and diameter of container (between 1.27 cm and 2.54 cm), have been shown to have no effect on the ease of ignition of each mixture. Addition of zinc oxide increases the minimum temperature of ignition from about 443 K to about 973 K and the minimum heating rate for ignition from about 2.5 watt to about 8 watt. The effect of zinc oxide is believed to be chemical rather than physical in nature.

Shock‐Wave measurements in water for calibrating the BICT‐Gap Test

Abstract: By means of shock-wave measurements it was possible to calibrate the BICT-gap test. The relation between the height of the gap and the shock-wave peak pressure at the end of the gap is described. From other considerations the range where the test can be used, can be obtained. BICT-gap test will be used to test explosives whose critical diameters do not exceed 20 mm and which will be initiated by shockwave pressures from 7 kbar to 60 kbar. The test method can be regarded as a small scale-gap test for military explosives.

Thermal Decomposition of Tetraethylammonium Perchlorate

Abstract: Thermal decomposition of tetraethylammonium perchlorate has been studied by thermogravimetry, differential thermal analysis and mass spectrometry. The title compound undergoes crystallographic transformation at 98°C and explodes at 298°C. The heat of phase transformation is calculated to be 2.5 kcal/mol. The mass spectral data suggest that the salt undergoes thermal decomposition into neutral particles which are then vapourized and ionized as well as oxidized.

The Detonation Properties of Explosive‐Water Mixtures

Abstract: Mixtures of crystalline explosive and water have as a rule detonation properties different from the dry material. It has been shown that the character of those changes is closely related to the structure of the particles (crystals, granules) of the explosives. The critical diameters and detonation velocities have been measured for a range of explosive-water mixtures, and the results are interpreted in terms of the hotspot theory.

Effect of Lead and Copper Methylene Disalicylates on the combustion rates of double‐base rocket propellants

Abstract: The effect of lead and copper methylene disalicylates and their mixtures was studied on the burning rates (35 kg/cm2-140 kg/cm2), heat of explosion, stability and thermal decomposition of double-base propelants. The results indicate that these salts are very effective catalyst and their mixtures produce super-rate burning (140% increase) with a uniform pressure index value in the entire pressure range. These additives lower “n” value to about 0.2–0.3 in some of the pressure regions. Results of DTA study suggest that these additives decompose in an exothermic mode in the temperature range close to the surface temperature of double base propellants.

Rapid Methods for Quality Control of Gun Propellants

Abstract: Several single-base, double-base, and triple-base gun propellants were analyzed by three different methods: Conventional analytical methods (TL 1376–600) High-pressure liquid chromatography (HPLC) Derivative spectroscopy. The results obtained by these methods agree well and show a good reproducibility. However, compared with each other, the chromatographic methods are not only more rapid and more flexible than the conventional wet chemical analysis, they enable a quantitative determination of blasting oil mixtures like nitroglycerin or diglycoldinitrate. The same holds for many other explosives, stabilizers and stabilizer reaction products.

Detonation Properties of 1,3,5‐Triamino‐2,4,6‐Trinitrobenzene when impacted by hypervelocity projectiles

Abstract: This investigation analyzes the reaction of an insensitive high explosive with binder to hypervelocity impact by four projectiles of two types: rod and plate. The insensitive high explosive is composed of 92.5% 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) and 7.5% Kel-F 800 binder, a vinylidene fluoride-chlorotrifluoroethylene copolymer. In this paper, for simplicity, we refer to this composition as “TATB”. Of the the impacting projectiles, three are steel-rod assemblies ranging in weight from 32.6 g to 34.6 g, and are composed of a steel rod 8 mm in diameter and 19 mm in length, of which 9 mm protrudes from a Polyzelux plastic holder. The fourth is a tantalum-plate assembly, weighing 23.9 grams and composed of a tantalum plate 24.2 mm in diameter and 1.5 mm in thickness mounted on a Polyzelux holder. The tantalum-plate experiment provides a highly efficient diverging detonation profile as predicted by similar previous investigations with flyer plates and TATB. The steel-rod experiments are compared to the tantalum-plate experiment to determine if detonation has occurred with the steel-rod impacts. The projectiles are accelerated by a two-stage, light-gas gun to velocities in the range of 3.1 km/s to 6.5 km/s (10,171 ft/s to 21,325 ft/s) and have bracketed the detonation threshold of the impacted TATB target. Comparisons of the TATB reaction data to a computer modeling of the experiment show that at 3.06 km/s, the computer model correctly predicts no initiation of detonation; at 4.75 km/s, the computer model correctly predicts a partial detonation; and at 5.67 km/s and 6.53 km/s, both the computer analyses and the experiments give divergent detonations.

Application of the Robbins‐Monro Method to the Sensitivity Testing of Explosives. I. A computer simulation study

Abstract: A computer simulation study of the Robbins-Monro method is presented. This method can be used to determine percentage points of a distribution function describing the probability of explosion as a function of some stimulus level. Calculations were performed to establish the influence of several parameters involved in the process. It is concluded that the method is suitable for determining 50, 10 and 1 percent points for several distribution functions. The efficiency for a restricted number of experiments and for a reasonable choice of the parameters is similar to that of a situation where experiments are performed at a fixed level, however with the advantage that the desired percentage point is obtained by convergence.

New Procedures for Purifying TNT

Abstract: Ammonium and magnesium sulfites were tested for purifying crude TNT in comparison with the conventional (“sellite”) process using sodium sulfite. The magnesium process easily gave an acceptable product in better yield, of higher quality, and at lower estimated cost. Magnesium values suitable for recycle were recovered from the waste water by calcination. The ammonium process gave an acceptable product only under specific reaction conditions, but the waste water can be recovered by mixing it with TNT process spent sulfuric acid, thereby eliminating a calcination step.

Etude mécanique de chargements moulé‐collés en propergol doublebase composite par Une méthode viscoélastique non‐linéaire

Abstract: L'article presente une methode d'etude mecanique de chargements moule-colles en propergol double-base composite (en abrege DBC) soumis a des cycles thermiques. La methode proposee pour determiner les contraintes et le coefficient de securite est basee sur le comportement non-lineaire et la compressibilite du propergol. Le comportement non-lineaire est obtenu d'apres des essais de traction. Les equations d'equilibre sont resolues numeriquement en decoupant l'epaisseur de propergol en plusieurs couches. Les non-linearites affectent essentiellement le module et on utilise un critere multiaxial et l'equivalence temps-temperature. On calcule a chaque pas de temps et pour chaque couche la temperature, le temps reduit, le facteur non-lineaire, le coefficient de Poisson, et le dommage (selon le concept de Farris). Differents types de chargements (bloc a canal central etoile, a mamelles, finocyl) ont ete soumis a differents types de cycles thermiques. La comparison entre prediction et experience est convenable meme pour des enchainements complexes d'allongement et de temperature.

On the Detonation Characteristics of CHNO‐Type Condensed Explosives. A parameter study

Abstract: The object of the present paper is to carry out a parametric study which takes into consideration the variations of the detonation characteristics such as CJ pressure, CJ temperature, velocity of detonation (VOD), and gas volume of CHNO-based condensed explosive systems in connection with the changes in input parameters like loading density and heat of formation of the explosive in question. Meaningful equations which describe adequately the interrelationships between the parameters were derived for a typical CHNO-type explosive. The study is likely to be of considerable help in determining the variations in the magnitudes of the detonation parameters corresponding to a given change in the relevant input characteristics. The results of such studies should also be important in estimating the uncertainty of a parameter, like VOD, arising from the uncertainty in the heat of formation of the explosive which is often determined experimentally and whose values is often of questionable validity. The principal features that emerge from the investigations in this paper are: (1) while CJ pressure and VOD tend to increase sizably with the loading density of the explosive, CJ temperature and CJ volume decrease with an increase in the loading density; and (2) all the four parameters, viz., CJ pressure, CJ temperature, VOD, and CJ volume increase, however, being of a marginal nature, barring the CJ temperature whose variations with the heat of formation are not insignificant.

Het powders, Propellants with Controlled Temperature Dependence

Abstract: After a general survey of conventional propellants, there will follow a description of the HET propellants. HET powders are propellants of heterogeneous structure. They are characterized by the powder granules worked into powder basic masses. The powder granules may be grains of single-base, double-base or triple-base propellants. Single-base powder basic masses are suited to take up a maximum of 70% granules. Granule percentages of about 50% have found to be most efficient. In the case of HET propellants with single-base matrix, their temperature dependence can be present at discretion, i.e. with neutral of negative temperature exponent, by the type, grain size and percentage of the granules worked in. HET propellants with single-base powders as basic masses can be produced with explosion heat values of up to 4300 Joule/g. Their manufacture does not present any problems and it is easy from the technical point of view. As full-strip propellants, the HET types with single-base powders as basic masses have progressive burning characteristic. HET propellant types are suited also for the manufacture of maccaroni and strip powder. The free-flowing powder types can be surface coated as usual.

Effect of Burning Rate Modifiers on Propellant Performance. A theoretical study

Abstract: The addition of burning rate enhancers or suppressers in solid propellant composition is seen to affect the energy level considerably. In the present paper, an attempt is made to quantify such effects. Even though the study is carried out over the theoretical values of the performance parameters, the trends in the variations and the corrections occurring therefrom for the inclusion of burning rate modifiers seem to be applicable to the delivered or the actual values also more or less equally.

Vereinfachte gasvolumetrische Gehaltsbestimmung von Diazodinitrophenol

Abstract: Diazodinitrophenol wird durch Reduktion der Diazonium-Gruppe zu molekularem Stickstoff in einer Sandmeyer-Reaktion mit CuCl oder durch Umsetzung mit TiCl3 quantitativ bestimmt. Da diese Reaktionen selektiv verlaufen, storen nitrogruppenhaltige Beimengungen nicht. Zur vereinfachten routinemasigen Durchfuhrung wird ein modifizierter Schulze-Tiemann-Apparat verwendet.

A Penalty Function Approach to the Optimization of Chemical Propellant Systems using the fletcher‐powell algorithm

Abstract: This article presents an efficient numerical algorithm for determining, for a given metallized propellant system, the optimum combination of reactants which can fetch the maximum specific impulse, and also the salient features of the associated computer program. The optimization procedure is based on the Fletcher-Powell technique with the objective function being augmented by a penalty term to accommodate the constraints. Numerical results for the optimization, obtained by means of a computer program written in FORTRAN IV on the IBM-360 computer for a representative propellant system, are also presented in this note.

Quelques propriétés physico‐chimiques des Solutions aqueuses de perchlorate d'ammonium

Abstract: La solubilite du perchlorate d'ammonium dans l'eau, la masse volumique, la viscosite, I'indice de reraction et la conductivite electrique des solutions aqueuses ont ete mesures et compares a d'autres valeurs de la bibliographie.