فصلنامه مواد پر انرژی
سال پانزدهم شماره 3 (پیاپی 47، پاییز 1399)

HMX and PETN explosives are the most important and usable explosives in the military and defense industries and possess wide range of applications for military as well as commercial applications. Numerous difficulties are encountered during the processing, conveying and storage of powders which are all attributed to their electrostatic charging. Indeed, charged powders could cause damage ranging from losses in quality and productivity to more severe accidents like explosions. In this study, paraffin / [H.mim][Cl] ionic liquid and paraffin/ lecithin were added to HMX and PETN explosives. Then they were studied by the powder volumetric resistivity test and electrostatic charging test setup. The accumulation of static charge was also measured. The samples were evaluated for further studies in the terms of mixing quality by FE-SEM and EDX analysis. In this work, the amount of reduction in static charge was considerably improved in the HMX and PETN samples, containing paraffin and lecithin was 56.67% and 66%, respectively and thermal stability was 25.15% and 36.15%, respectively. Adding ionic liquid with paraffin to HMX and PETN explosives, the amount of reduction in static charge was significant and was about 106.66% and 100%, respectively.

In this research, the catalytic reforming of kerosene fuel was performed in order to investigate the production of jet propellant fuels. For this purpose, at first the role of catalysts in the process of jet fuel production was surveyed. Then, two catalysts of Ni supported on Al2O3 and Ni supported on ZSM-5 was applied as a case study in a fixed bed reactor. The applied catalysts in this research were prepared by deposition-coprecipitation method and their properties were characterized through XRD, EDX, NH3-TPD, and BET analysis. The results of data analysis of liquid phase in the process output showed that applying zeolite catalyst led to production of some products with different properties such that some of these products meet the requirements of valuable products such as jet fuels. The reason was the increase in naphthene content of the produced fuel (from 26.49% in feed to 46.28% over Ni/ZSM-5 catalyst) via catalytic reforming of kerosene. This result leads us to conclude that applying zeolite catalysts considerably increases the ability of kerosene as a feed for reforming process to synthesize jet propellant fuels.

Despite the unique properties of epoxy resins, their use is limited in many cases due to their low impact resistance. One of the methods to overcome this limitation is to use compounds for increase Toughness such as carboxyl-terminated butadiene acrylonitrile (CTBN) (94% Wt.) in the epoxy matrix. In this study, the curing reaction of CTBN with 1,2,7,8 diepoxyoctane (DEO) (5% Wt.) in the presence of two types of amine 1, 1′-Isophthaloyl bis (2-methylaziridine) (HX-752) and triethanolamine (TEA) as catalyst is investigated. In order to evaluate the performance of the proposed binder, elastomers with different formulations were prepared and tested for mechanical and thermal properties. The results of mechanical and thermal properties of elastomers produced in the presence of TEA in comparison with HX-752 showed that the tensile property (234.2%), cross-linking density (111.8), storage modulus, and glass transition temperature (43.9°C) have increased. Due to the improvement of the properties, it is predicted that the produced binder can be used in the formulation of composite solid propellants and PBX explosives, as well as liner and insulation coatings with proper performance.

Several parameters affect the rheological and mechanical properties of solid composite propellants. Among them, the molar ratio of isocyanate (NCO) to hydroxyl (OH) groups (i.e. R value) is one of the important factors. In this research, the effects of changing the weight ratio of dimeryl diisocyanate (DDI) curing agent related to hydroxyl terminated polybutadiene on different properties of a HTPB based solid composite propellant such as end of mix viscosity, time depending behavior of viscosity, tensile stress, elongation, elastic modulus and hardness is investigated. For this purpose, five propellant formulations were prepared with various R value in the range of 0.755 to 0.815. Results showed that as the R value increased, end of mix viscosity is reduced at the first due to the wetting effect resulting from DDI addition and then is increased because of progressing of curing process. Furthermore, the mechanical properties are enhanced by increasing the R value, whereas elongation at maximum stress is reduced about 20%.

In the current research, 3D simulation of the projectile movement with a diameter of 5.56 mm, has been considered in the barrel with 48.26 cm length. The ideal gas and Abel-Nobel equations of state have been used to solve the gas phase equations. 6DOF solver has been applied to evaluate the projectile- fluid interaction and solved in the coupled manner with continuity, momentum, and energy equations. To reduce the computational time, the projectile initial position was considered 15cm farther from the breech and initial conditions have been obtained from Quickload software and introduced into Fluent. In the experimental study, two light screens and an electrically insulated firing pin have been used to measure the muzzle velocity and projectile exiting time. The relative deviations of the ideal gas and Abel-Nobel equations of state were almost 6.38, 0.76 percent in muzzle velocity, and 1.1, 0.21 percent in residence time computations respectively. The simulated transient velocity of the projectile was also compared with Quickload software results and the close agreement was achieved. Simulation results include temperature, velocity, and pressure contours inside and outside of the barrel during the projectile movement. Temperature-time, pressure-time, displacement-time, and velocity-time curves of projectile were reported using ideal and Abel-Nobel gas equations of states and compared. Also, one of the important results of the simulation was the computation of force exerted on breech which was obtained 5341 N in the present study.

Recognizing the effective parameters on liquid fuel degradation and its shelf life prediction is an important issue. Most of the researches done in this area are limited to synthetic fuels. In this work, the shelf life of hydrocarbon fuel and the effect of vessel material, blanketing gas and vessel temperature on the amount of generated gum in the fuel have been investigated. The results showed that both aluminum and stainless steel materials are suitable for storage vessel. Moreover, the amount of gum reduces to one-ninth by nitrogen rather than oxygen. Therefore, the stainless steel vessels with nitrogen blanketing gas have been utilized for accelerated ageing tests. According to kinetic studies, the reaction of gum generation was of zero order and the reaction rate constants and the shelf life of fuel at 20, 30 and 40 °C were predicted to be 0.00254, 0.00616 and 0.0141 mg/ 100 ml. day and 43.4, 17.9 and 7.8 months for Arrhenius approach and 0.00299, 0.00639 and 0.0136 mg/ 100 ml. day and 36.6, 17.2 and 8.1 months for Berthelot approach, respectively.