Showing papers in "Propellants, Explosives, Pyrotechnics in 1979"
TL;DR: In this article, it was shown that polynitroaromatic explosives containing a C-H linkage alpha to the aromatic ring are more sensitive as a class than explosives lacking such a linkage.
Abstract: Impact sensitivities of organic high explosives are primarily functions of the rates of the thermal decomposition processes taking place in the temperature regimes generated under the impact hammer. For classes of explosives with similar decomposition mechanisms, there appear to be statistically significant linear relationships (sensitivity/composition trends) between logarithmic 50% impact heights and values OB100, a measure of oxidant balance. In addition, it is shown that polynitroaromatic explosives containing a C-H linkage alpha to the aromatic ring are more sensitive as a class than explosives lacking such a linkage. These results are consistent with the finding that products of thermal decomposition of TNT indicate a preferred site of inter- and intramolecular oxidative attack to be at the alpha C-H linkage.
326 citations
TL;DR: In this article, the volume coefficient of thermal expansion for crystalline TATB is 30.4 × 10−5 K−1, where K is the number of cells in a sheet.
Abstract: Expansion of TATB is studied on a molecular level by means of x-ray crystallography. Continuous monitoring of the cell constants of TATB between 214 K and 377 K allows calculation of a volume change of +5.1% for this molecular system. Expansion of the pure material is almost exclusively a function of a 4% linear increase in the c axis (the perpendicular distance between sheets of hydrogen-bonded TATB). Calculated from these data, the volume coefficient of thermal expansion for crystalline TATB is 30.4 × 10−5 K−1. The structural features of crystalline TATB and its anisotropic thermal-expansion behaviour are compared with those of graphite and boron nitride. Two other crystalline products in the bulk TATB are either actual polymorphs of TATB or impurities.
124 citations
TL;DR: In this article, a simple linear relationship between detonation velocity of 64 ideal C,H,N,O type explosives at their theoretical maximum densities (TMD's) and a factor was described.
Abstract: An earlier paper(1) described a simple linear relationship between detonation velocity of 64 ideal C,H,N,O type explosives at their theoretical maximum densities (TMD's) and a factor. F, that is dependent solely upon chemical composition and structure. Based upon available experimental data for nine fluorine-containing explosives, the equation for calculating the factor has been expanded to include compositional terms for fluorinated compounds. In addition, the reliability of the linear relationship has been further tested against seven more recently published C,H,N,O type explosive experimental detonation velocity data points. The calculated detonation velocity values for all 16 explosives lie within 6.0% of experimental with an absolute error of ± 3.0%.
101 citations
TL;DR: In this article, the relation entre structure electronique et sensibilite au choc, deja effectuee sur les nitroaromatiques et les nitramines, is investigated.
Abstract: Dans cet article, nous avons etendu aux esters nitriques l'etude de la relation entre structure electronique et sensibilite au choc, deja effectuee sur les nitroaromatiques et les nitramines. On y verifie la validite du critere moleculaire de sensibilite au choc precedemment etabli. Ce travail permet, en outre, de proposer une echelle de sensibilite au choc englobant les explosifs organiques des primaires aux secondaires les moins sensibles.
65 citations
TL;DR: In this article, it was shown that the break-time of homogeneous ductile metals under very high strain rates is equal to the smallest initial dimension of the elongating metal divided by VPL.
Abstract: It was found that the breakup-time of jets formed by shaped charges of cylindrical symmetry is given very accurately by the formula:
This formula is obtained from a general principal applied here for the first time which says that the breakup-time of homogeneous ductile metals under very high strain rates is equal to the smallest initial dimension of the elongating metal divided by VPL. When applied to simple configurations such as a pipe which expands due to internal explosion this principal leads to a correct prediction of the average formed fragment dimensions. This principal provides for the first time an explanation to the experimental fact that metals' ductility can increase by an order of magnitude when the strain rate increases from 10−2 to 105 pro second.
45 citations
TL;DR: In this article, the influence of interactions between cristallines on the parametres moleculaires correles a la sensibilite au choc lors de precedents travaux is examined.
Abstract: On etudie l'influence des interactions cristallines sur les parametres moleculaires correles a la sensibilite au choc lors de precedents travaux. Les resultats obtenus permettent de mieux preciser les rǒles respectifs de la molecule et du cristal lors de l'initiation de la detonation. Ils montrent que dans ce domaine, les conclusions tirees de calculs effectues sur une molecule isolee dans sa conformation cristalline sont valables pour le cristal entier.
38 citations
TL;DR: In this article, the synthesis of 2,2′,4,4′,6,6′-hexanitrostilbene by oxidative coupling was studied in the presence of metal catalysts and the effects of reaction parameters on product yields were evaluated and mechanisms for the reaction were proposed.
Abstract: The synthesis of 2,2′,4,4′,6,6′-hexanitrostilbene by oxidative coupling of 2,4,6-trinitrotoluene in the presence of metal catalysts has been studied. The effects of reaction parameters on product yields have been evaluated and mechanisms for the reaction are proposed.
17 citations
TL;DR: The performance of an explosive is a function of both the peak energy released near the detonation front, and the remainder of the energy that is released during the Taylor wave as discussed by the authors.
Abstract: The performance of an explosive is a function of both the peak energy released near the detonation front, and the remainder of the energy that is released during the Taylor wave. The relative partitioning of energy between the front and the expansion, and the rate of energy release in the latter, may be controlled by either chemical kinetic or diffusion processes. Detonation calorimetry has been the principal experimental technique used to investigate these processes. Both the total energy release, and the quantitative analysis of the detonation products at a point or region on the expansion isentrope have been determined for formulations of ammonium nitrate (AN) and TNT in which both the composition and particle size of the AN have been varied. Isotopic labeling of selected explosives has also been used to give further insight into the reactions taking place in or near the reaction zone. Similar experiments have been performed in an ideal, homogeneous explosive.
16 citations
TL;DR: In this article, the ignition behavior of a solid propellant composed of 25 wt% polybutadiene and 75% ammonium perchlorate under sub-atmospheric conditions has been studied using a carbon dioxide laser whose radiant flux is uniformalized.
Abstract: Ignition behavior of solid propellant composed of 25 wt% polybutadiene and 75% ammonium perchlorate under subatmospheric conditions has been studied using a carbon dioxide laser whose radiant flux is uniformalized. Data of ignition time in Ar, N2 and He atmospheres, and critical radiant flux and pressures over which ignition might be achieved, were obtained. Moreover, the data were compared with theoretical values, taking account of variable heat conductivity for the ambient gases with a surface ignition hypothesis.
It is concluded that these ambient gases participate in the pre- and post-ignition reactions and the ignition preventive behavior of He atmosphere is not predictable merely based on its high transport properties. The detailed observation of the ignition transient near the critical pressure revealed that the ignition in Ar atmosphere occurs in gas phase under less than 100 torr whereas in He atmosphere it occurs always at the condensed phase surface.
13 citations
TL;DR: In this article, the problem of crack growth in a nitrocellulose/nitroglycerin propellant has been studied employing a continuum fracture mechanics approach and the value of the stress-intensity factor at the onset of crack propagation has been ascertained and found to be dependent upon both the thickness of the specimen and the test temperature.
Abstract: The problem of crack growth in a nitrocellulose/nitroglycerin propellant has been studied employing a continuum fracture mechanics approach. Values of the stress-intensity factor, Kc, at the onset of crack propagation have been ascertained and found to be dependent upon both the thickness of the specimen and the test temperature. By proposing that the value of Kc arises from the sum of a plane-strain and a plane-stress component a unique failure criterion, which is constant over a wide temperature range, has been identified. Namely, that crack propagation in the propellant occurs when the plane-stress plastic-zone at the crack tip attains a critical size.
11 citations
TL;DR: In this paper, the authors used differential scanning calorimetric, thermogravimetric and mass spectrometric techniques to study double-base propellants in air and vacuum.
Abstract: Thermal decomposition studies on double-base propellants have been carried out in air and vacuum using differential scanning calorimetric, thermogravimetric and mass spectrometric techniques. Low temperature (90 degree C-170 degree C) decomposition seems to involve diffusion controlled process, the mechanism in air and vacuum being different. High temperature (170 degree -205 degree C) decomposition involves bond breakage.
TL;DR: In this paper, the authors derived expressions for the burning rate pressure exponent and the temperature sensitivity of AP-based and HMX-based CMDB propellants in terms of the respective physical constants.
Abstract: The object of this paper is to obtain expressions for the burning rate pressure exponent and the temperature sensitivity of AP-based and HMX-based CMDB propellants in terms of the respective physical constants on the basis of a recently developed model of combustion for CMDB propellants and to examine the effects, if any, on these two parameters, of the changes in propellant composition, AP particle size and pressure. Computer programs were developed for this purpose and the results obtained for typical sets of input data presented in the paper. While the results of the calculation indicate a markedly strong dependence of the pressure exponent and the temperature sensitivity on pressure and composition for both AP-based and HMX-based CMDB propellants, the parameters are characterized by far lesser dependence on AP particle size for the AP-based propellant.
TL;DR: In this article, the optical properties of small droplets of aqueous solutions of zinc chloride were studied in the 3 μm to 12 μm spectral range, generated by combustion of a pyrotechnic screening smoke composition containing hexachloroethane and zinc.
Abstract: Optical properties of small droplets of aqueous solutions of zinc chloride were studied in the 3 μm to 12 μm spectral range. The droplets are generated by combustion of a pyrotechnic screening smoke composition containing hexachloroethane and zinc. Mass extinction coefficients were determined and interpreted by the theory of Mie.
The optical constants of aqueous solutions of zinc chloride are markedly different from those expected for a screening smoke of low IR transparency.
TL;DR: In this article, a composite explosive was submitted to accelerated aging at 293 K, 333 K and 353 K for slightly over a year, and extensive determination of mechanical properties were conducted using an Instron Tester to characterize the aging process of the explosive.
Abstract: A given formulation of a composite explosive was submitted to accelerated aging at 293 K, 333 K and 353 K for slightly over a year. Extensive determination of mechanical properties were conducted using an Instron Tester to characterize the aging process of the explosive as a whole. The change of elongation at maximum load can be fitted to a third-order reaction rate giving an enthalpy of activation (Δ Ha) for the aging process of (78 ± 5) kJ/mol. Although the change of stress at maximum load was a function of temperature, it could not be predicted by a simple correlation. Swelling, inverse gas chromatography and N2O evolution by infrared were applied to the samples aged at 333 K. Swelling measurements show a regular increase with aging of the relative number of cross-linking. Inverse gas chromatography at 373 K in helium indicated a first-order kinetic aging process for every sample, but the rate constant (k) of the samples aged for 0, 30 and 60 days was slightly lower than the one for samples aged for 130, 250 and 375 days. The N2O evolution measured at 338.5 K in vacuum by infrared absorption indicates an aging process consisting of two consecutive first-order reactions, the second one being ten times slower than the first one. The first stage, which was also studied by inverse gas chromatography, gives rate constants which are about half as large as those measured by chromatography and confirms the changes in behavior from the samples aged for 0, 30 and 60 days to the samples aged for 130, 250 and 375 days. These results are discussed in relation to an aging process by oxidative cross-linking of the binder and degradation of the solid explosive.
TL;DR: In this paper, the authors used laser induced chemistry to synthesize decaborane-14 from diborane in high yields and high purity using both CO2 and DF laser frequencies.
Abstract: n-Hexylcarborane (NHC) is the proposed burning rate modifier for improved propellants to be used in the next generation of missiles. The synthesis of this material requires decaborane-14, a material that is not commercially available in large quantities now. Therefore, the cost-effectiveness of synthesized NHC, as it relates directly to the missile cost, depends upon a low-cost synthesis of decaborane-14. Laser induced chemistry, a revolutionary new kind of chemistry, offers a much more efficient and less expensive way to synthesize compounds than conventional thermochemistry provides. Using this technique, we have synthesized decaborane-14 from diborane in high yields and high purity using both CO2 and DF laser frequencies. The products are decaborane-14 formed as white crystals and pentaborane-9 in the gaseous state; thus, isolation of the decaborane-14 is a simple chemical engineering procedure.
TL;DR: In this paper, the effect of fine and coarse Al on the deflagration-to-detonation (DDT) behavior of HMX, is charges pressed to 90% theoretical maximum density (TMD), was studied.
Abstract: : The effect of fine (5 microns) and coarse (95 microns) Al on the deflagration-to-detonation (DDT) behavior of HMX, is charges pressed to 90% theoretical maximum density (TMD), was studied. It was found that Al slows down the DDT process increasingly as the content of Al increases; that is, it increases predetonation column length and the relative times to detonation. Fine Al is more effective than coarse in delaying DDT, at a given content , but both are inferior to wax in this respect.
TL;DR: In this paper, a new method for castloading of explosive charges is described, where the state of the explosive is changed by applying pressure which causes an immediate rise of the melting point according to Clausius-Clapeyron's equation.
Abstract: A new method for cast-loading of explosive charges is described. Up to now cooling was used to solidify the melt of the explosive. In this method the state of the explosive is changed by applying pressure which causes an immediate rise of the melting point according to Clausius-Clapeyron's equation. The total melt solidifies immediately and uniformly. The method has the advantage that voids are avoided and short loading times are obtained if the melting point is raised in this manner to the temperature momentarily present in the explosive.
TL;DR: Ammonium nitrate and ethylenediamine dinitrate in a composite have been determined by potentiometric titration with standard base after reaction with formaldehyde in this article.
Abstract: Ammonium nitrate and ethylenediamine dinitrate in a composite have been determined by potentiometric titration with standard base after reaction with formaldehyde Ethylenediamine dinitrate yields two breaks, while ammonium nitrate exhibits only a single potentiometric break Both components can therefore be resolved The first potentiometric break is a measure of the ethylenediamine dinitrate content, while the second break is a measure of the sum of the components
TL;DR: In this paper, the increase in temperature by shock-compression of nonporous high explosives was calculated by the Walsh-Christian technique, which was extended to porous media, and the results were discussed.
Abstract: The increase in temperature by shock-compression of non-porous high explosives was calculated by the Walsh-Christian technique. Extension of this model to porous media enabled us to calculate the increase in temperature of shock compressed porous high explosives at different loading densities. As an example, calculations have been performed for Composition B at different loading densities. The results are discussed.
TL;DR: A gas-liquid chromatographic procedure was developed in connection with the determination of water in nitroglycerin-nitrocellulose pastes as discussed by the authors, which is based on the reaction of water with 2,2-dimethoxypropane and its conversion to acetone which is subsequently determined.
Abstract: A gas-liquid chromatographic procedure was developed in connection with the determination of water in nitroglycerin-nitrocellulose pastes. The method is based on the reaction of water with 2,2-dimethoxypropane and its conversion to acetone which is subsequently determined. The technique is simple, rapid, and shows good accuracy and precision.
A simplified method, which is less accurate but does not involve chromatography, is also proposed.
TL;DR: In this article, a caractere radicalaire de la decomposition thermolytique de la nitroglycerine is presented, and a serie of reactions secondaires aboutissant aux produits de reaction observes.
Abstract: Par l'utilisation de methodes analytiques modernes, telles que la resonance paramagnetique electronique, la spectrophotometrie infrarouge avec etude des deplacements de masse, la spectrometrie de masse et la fragmentometrie, combinees avec des analyses de gaz et des couplages chromatographie-spectrometrie de masse, on a pu mettre en evidence le caractere radicalaire de la decomposition thermolytique de la nitroglycerine, puis proposer une serie de reactions secondaires aboutissant aux produits de reaction observes.
TL;DR: The Resonance Magnetique Nucleaire Impulsionnelle permet l'etude de systemes constitues de plusieurs phases de mobilites differentes as mentioned in this paper.
Abstract: La Resonance Magnetique Nucleaire Impulsionnelle permet l'etude de systemes constitues de plusieurs phases de mobilites differentes. Nous presentons ici une application de cette technique a l'examen du phenomene de plastification du nitrate de polyvinyle au phtalate de dibutyle. Dans ce materiau, on met ainsi en evidence les phases suivantes:
polymere rigide,
polymere mobile,
plastifiant rigide,
plastifiant mobile.
Ces differentes phases sont suivies quantitativement en fonction du taux de plastifiant et de la temperature.
TL;DR: In this article, a rapid method for simultaneous determinations of nitroguanidine and nitrate ion in the spent sulfuric acid has been developed, which consists of merely diluting an aliquot of sample with water and measuring the absorbances of the two compounds at 265 nm and 203 nm, respectively.
Abstract: A rapid method for simultaneous determinations of nitroguanidine and nitrate ion in the spent sulfuric acid has been developed. This method consists of merely diluting an aliquot of sample with water and measuring the absorbances of nitroguanidine and nitrate ion at 265 nm and 203 nm, respectively. In the concentration ranges studied, average accuracies of better than 1% and 2% were obtained for nitroguanidine and nitrate ion, respectively. The precision was better than 1% in both cases.
TL;DR: In this article, the authors present an analysis of the relationship between oxygen balance, inert content, computed detonation parameters and incendivity for several water-gel explosives, and a mathematical technique is developed for correlating compositional details and the permissibility test result for a number of existing compositions.
Abstract: This paper presents an analysis of the relationship between oxygen balance, inert content, computed detonation parameters and incendivity for several water-gel explosives. A mathematical technique has been developed for correlating compositional details and the permissibility test result for a number of existing compositions. The analysis covers two types of explosive compositions and three categories of permissibility tests. Using energy of detonation, oxygen balance and percentages of water and sodium chloride in the composition, this technique is able to consistently predict the permissibility test result with less than 10% exceptions. It is felt that this method will facilitate the design of new explosive formulations which have a high probability of success in permissibility tests.