فصلنامه مواد پر انرژی
سال هجدهم شماره 2 (پیاپی 58، تابستان 1402)

Physical properties are among the quality control characteristic of paste explosives. Optimizing the proportional amounts of component in a composite paste explosive can have a significant effect on improving the physical properties. In this research, the effect of the amounts of different classes of RDX with different particle sizes distribution is studied on the physical properties (plasticity, density and binder leakage) of paste explosive RDX/DOS/PIB (90:2.5:7.5). The experimental design - response surface method was used to optimize the amount of each classes of RDX. The particle size distribution of RDX classes has been investigated by FE-SEM method. The average size of RDX particles in classes 1, 3 and 5 were obtained as 144.9, 441 and 3.6 microns, respectively. Plasticity of 0.029, density of 1.513 g/cm3 and the binder leakage of 0.034% are obtained for the optimal amounts of 52.5, 7.5 and 30 grams of RDX from classes 1, 3 and 5 respectively, in 100 gram sample of the proposed paste explosive.

Today, vacuum stability test is one of the best methods to investigation the compatibility of different plasticizers and polymers. In this research, the compatibility of polydimethylsiloxane resin with trimethylolethane trinitrate energetic plasticizer was investigated. The applied approaches included vacuum stability test (VST) and glass transition temperature determination using DSC analysis. The acceptance limit of TMETN plasticizer by polydimethylsiloxane resin was determined using retardation and it was found that this polymer can accept the plasticizer at least 20% (w/w). Investigating the glass transition temperature with DSC analysis test showed that polydimethylsiloxane has good compatibility with TMETN plasticizer. The amount of gas released from the sample in standard conditions (VR) in the VST test was calculated as 4.77 cm3, which was within the allowed range and indicates the compatibility of TMETN plasticizer with polydimethylsiloxane.

Cobalt disulfide nanoparticles have been used as cathodes in thermal batteries due to their unique properties. Herein, cobalt disulfide was synthesized by Solvothermal method. Investigations showed that for synthesis, the reaction should be carried out at temperatures higher than 150 degrees Celsius. XRD, FESEM, EDS, and ICP analysis were performed and the density, particle size, and frequency distribution diagram of the samples were calculated for quality control. According to XRD analysis, three samples were crystalline and eight samples were amorphous. ICP analysis was taken from three samples, which showed the best synthesis sample of cobalt (47.5%) and sulfur (52.5%). According to the results of various analysis, the best synthesis sample of cobalt disulfide in terms of crystallinity and higher density (0.66 g/cm3) and higher particle size (114.26 nm) was selected and introduced as the optimal sample for use in thermal batteries.

Dimeryl diisocyanate (DDI), one of the most frequently used isocyanate curing agents for propellant, DDI is used to cure solid propellants based on HTPB. Diisocyanates are used as a curing agent in HTPB-based composite solid propellant systems. In this study, a three-step process for optimizing the effects of numerous parameters in the manufacture of dimeryl diisocyanate (DDI) was used. In the first step, the reaction with ethanol at a temperature of 85 degrees Celsius led to the preparation of the dimer ester compound with a yield of 99%. In the following stage, high temperatures and no solvent are used to combine the produced dimer ester with hydrazine hydrate to create dimer hydrazide. In the third stage, acyl azide is produced using sodium nitrite, and the target product is produced with a 90% yield using a high-temperature Curtius rearrangement. The product obtained by this method does not have the disadvantages of the phosgene method.

In this study, multiple linear regression (MLR) was used as a safe, fast, inexpensive and common method to predict impact sensitivity of energetic cocrystals. For this purpose, the data related to 28 of energetic cocrystal compounds were collected from different reliable references. Then various descriptors such as topological, structural, sub structural and … descriptors were calculated using DRAGON software. The results showed that optimum elemental composition and number of nine-member rings in the cocrystal structure are the most effective descriptors in this model. Determination coefficient of the new model was 0.954 for 22 members training set and root mean square deviation (RMSD) and average absolute deviation (AAD) were calculated as 4.55 and 3.53 J, respectively. Also, RMSD and AAD for six members test set as external validation were derived 4.48 and 3.34 respectively. Also, RMSD and AAD were 4.36 and 3.95 respectively for cross validation of derived model. For investigating of predictability of the new model were used two cross validation method as internal validation. The results showed that the values (Q2LOO=0.927 and Q2LMO=0.958). The Roy et. al computations were also used for confirmation of internal validation.

In addition to the inherent characteristics of explosives, the power of the detonation is affected by arrangement of the explosive train. Therefore, the correct design of the explosive train, especially for insensitive explosive charges containing aluminum, play a fundamental role in order to be more effective. In the current research work, by changing the dimensions of the booster pellet and its position relative to the main charge; the detonation behavior of the main charge has been investigated. In this study, the booster pellet (COMP-A3) is modeled with JWL equation of state and the main charge (PBXN-111) is modeled with ignition and growth equation of state. The simulations has been done using AUTODYN software. The coefficient used in the equation of state (ignition and growth) has been evaluated with experimental results. The simulation results show that by reducing the diameter of the booster pellet from 5cm to 3cm, for a certain length of the booster pellet, reaching to the steady detonation increases due to the greater divergence of pressure wave into the charge. In the case where the booster is inside the charge, the peak pressure values increase in the corners of the charge and adjust the pressure drop due to the divergence. The simulation shows that for the case where the booster and the main charge are placed on top of each other, the booster with a diameter of two centimeters with any length of the booster pellet is not able to create stable detonation in the main charge. For a submerged condition of the same diameter, the booster can produce stable detonation in the main charge. This study showed that a booster pellet with a diameter of 5 cm and a length of 4 cm can cause a complete detonation in PBXN-111. The length of the region to reach stable detonation with this booster is 15 cm.