فصلنامه مواد پر انرژی
سال چهارم شماره 2 (پیاپی 8، پاییز و زمستان 1388)

1,1-Dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH) is one of the hydrazine derivatives that is mainly used as a high-energy fuel in military applications as a rocket propellant and as a fuel for thrusters, and small electrical power generating units. 1,1-Dimethylhydrazine is volatile and toxic, and is readily absorbed by oral, dermal or inhalation routes of exposure. Because of the environmental and toxicological significance of 1,1-dimethylhydrazine, sensitive and reliable analytical methods are necessary for determination of 1,1-dimethylhydrazine in samples. In this paper, a new spectrophotometric method for the determination of trace amounts of 1,1-dimethylhydrazine is described. The method is based on the reaction of 1,1-dimethylhydrazine with p-nitrobenzaldehyde in micellar media. The optimal reaction conditions were studied and the analytical characteristics of the method were obtained. The method allowed the determination of 1,1-dimethylhydrazine at concentration between 0.40 – 6.0 mg.mL-1 with detection Limit (DL) of 0.1mg.mL-1 and relative standard deviation of 1.45%, respectively. Under working conditions, the proposed method was successfully applied to the determination of 1,1-dimethylhydrazine in water samples.

In this article, the detonation wave propagation in the ideal and non-ideal high explosives has been studied and compared. This study is performed utilizing the Wood-Kirkwood theory (WK theory), which is valid for slightly curved self-sustained detonations. Utilizing this model, a relation between detonation velocity and the front curvature is obtained. In this study, it has been shown that non-ideal explosives are poorly modeled by Chapman-Jouguet (CJ) theory. Comparison of the results of WK model with empirical data reveals that WK model has good accuracy in modeling detonation propagation in non-ideal explosives, especially for small curvatures. The present study shows that of the accuracy of state equations, the employed burning rate, their calibration, and also the mixture rules influence the results considerably.

A kinetic study of the reaction between a hydroxyl-terminated poly butadiene (HTPB) and isophorone diisocyanate(IPDI) was carried out by using back titration. At four temperatures 30, 40, 50 and 60 degrees centigrade, the progress of reaction, rate constant and activation energy were obtained. It was shown that reaction has an apparent second -order in terms of HTPB and IPDI concentration. In the second-order plots, a discontinuity was observed. This behavior depends on differences in reactivity of the isocyanate groups at isophorone diisocyanate molecule site. The activation energies for the two parts of the reaction were determined to be 8.3 and 10.1 Kcal/mole.Next, effects of curing ratio parameter (equivalent ratio of NCO/OH) and ferric Acetyl Acetonate catalyst for butadiene polymerization were investigated. Results of this research shows that a discontinuity exist at second-order plots.The IPDI molecule is a cycloaliphatic diisocyanate that includes a group of first type isocyanate (CH2-NCO) and a group of second type isocyanate (CH-NCO). This activity difference of these groups produce a discontinuity at second-order plots. In the next phase of the study, effect of temperature, type of isocyanate and catalyst on the reachen system was investigated. Finally, a comparative kinetic study between the three different diisocyanates, i.e, Toluene diisocyanate (TDI), hexametylene diisocyanate (HMDI) and isophorone diisocyanate), was carried out. It was observed that the order of reactivity for diisocyanates was aromatic, aliphatic and cycloaliphatic. Considering this finding, we can select adiisocyanate appropriate for the reaction in question.

In this study, the reactive Euler equations are solved in the reaction zone between the leading shock and sonic locus for curved detonations propagating in high explosives. The explosive material is described by general equation of states and reaction rate law. The investigation is carried out by the "Detonation Shock Dynamics" (DSD) method. The effects of the front curvature on the detonation velocity and its properties are determined for divergent and convergent detonations. Governing equations are written in shock attached frame and simplified assuming small detonation front curvature (relative to half-reaction length) and slow-varying shape (relative to particle pass time through reaction zone). It is observed that increasing the front curvature leads to decreasing of the diverging detonation velocity relative to the corresponding ZND detonation. Besides, for curvature higher than a critical limit the detonation fails. Decreasing the converging detonation curvature radius causes a dramatic increase in the detonation velocity and pressure. In the reaction zone of the high explosive materials, the reactant and products exist simultaneously. Computation of the mixture properties needs some assumptions known as the mixture rule. In the present work, the effects of the mixture rule on the planar and curved detonation is studied. It is demonstrated that the kind of the mixture rule does not have considerable effects on the planar detonation. However, its effect on the curved diverging detonation is significant and leads to a substantial change of the detonation properties such as the velocity and pressure.

The detonation of explosive materials in a cylindrical shell releases abruptly a large amount of energy that may cause fracture of shell to a number of fragments with various shapes, sizes and masses. There are several methods for controlling fracture such as creating grooves on the surfaces of the cylinder. The depth, direction and cross section of the grooves and the distance between the grooves are important parameters for the fracture control of cylinders. The numerical simulation of fracture can be one of the most appropriate techniques for studying this phenomenon and for reducing the number of complicated, expensive and dangerous experiments that have to be performed. In this paper, the first fracture of a cylindrical shell under explosive loading is simulated numerically using the code LS-DYNA (CLE Method) and then the effects of groove arrangements on the cylinder fragmentation are evaluated. The results show that the longitudinal grooves have the major effect in controlling fracture. However, by choosing appropriate groove depths one may control the fragmentation both in the axial and in the circumferential directions. Moreover, the external grooves are not suitable for controlling the fragmentation.

In this research work, a computer code is developed to predict the detonation properties of high explosives on the basis of the Chapman-Jouguet theory. A new free energy minimization scheme was employed to calculate the equilibrium composition of non-ideal and multiphase mixture of detonation products. The new minimization scheme is a variant of the Newton-Raphson algorithm. In the present work, the second derivatives of free energy are computed for non-ideal mixture. It is found that the developed algorithm calculates the chemical equilibrium properties more accurately than the FORTRAN BKW scheme which takes the second derivatives of free energy as equal to their values in a perfect gas mixture. The calculated detonation velocities and C-J pressures are compared with experimental data as well as the data reported from other thermo-chemical codes. The results are very promising.

Binders and plasticizers containing energetic groups such as nitro (-NO2), fluorodinitro (FC(NO2)2-), difluoroamino (-NF2), azide (-N3) and nitrate (-ONO2) have been developed and used in formulation of energetic materials. In this research paper, the synthesis of a high N-component energetic material possessing both energetic functional groups ONO2 and N3 in its molecular structure has been investigated. This compound is Azidodeoxycellulose nitrate(II). To reach the target molecule, nitration of azidodeoxycellulose(I) was performed using acetic anhydride, 98% HNO3 at 0◦C in CH2Cl2 Solvent. The presence of azido groups and the enhancement of nitrogen percent were confirmed by IR spectroscopy and elemental analysis. The heat of explosion and the volume of the obtained gas were investigated by calorimetric and gasometric methods respectively.