JOURNAL OF ENERGETIC MATERIALS
Year:2018 | Volume:13 | Issue:2 (38)|Papers Count:7

In various industries utilization of rubbers is an obstacle due to the generation of superficial stress at the surface of rubber, resulting superficial cracks and reducing the service life of rubber parts. These stresses are usually caused by friction between the surfaces of rubber and metal. Roughness of surfaces, composition of rubber compounds, environmental conditions and test settings affect the rubber– metal friction. Surface roughness plays an important role in sliding between two surfaces and controls friction behaviors. On the other hand, the effect of roughness on the friction coefficient is controllable using a suitable lubricant. In the present study regarding to the fuel consumption in rubber fuel tanks and selflubrication characteristic in majority of fuels, the effect of JP-10 & DMAZ fuels as lubricants is investigated to reduce the sliding friction coefficient between NBR and aluminum with various roughness. The results show the relation between the sliding friction coefficient and the mean surface roughness (Ra). By applying JP-10 & DMAZ fuels as lubricant, the coefficient of friction decreased by almost 65% and 85%, respectively.

Ammonium perchlorate (AP) is considered as a strong oxidizer in solid propellants. Therefore, it s thermal decomposition characteristics has a direct influence on the combustion behavior of solid propellants. The AP particle size, shape, and morphology influence thermal behavior. In this study, For the first time the solvent-anti-solvent crystallization method equipped with an eductor mixer was used for the production of propellants oxidizing materials. The eductor easily increases the quality of mixing and does not increase the cost of launch and utilization. The crystallinity of produced ammonium perchlorate and reference samples were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. The results showed that the produced crystals in this system have a regular morphology and were crystallized in the form of an orthorhombic structure. On the other hand, the growth of the crystal in plane (011) of the produced samples is attenuated compared to the reference sample and the growth in (210) plane is greater than those of reference sample. Thermal behavior analysis by thermogravimetric analysis (TGA) showed that the produced sample has a one-step decomposition peak while in the reference sample, a two-stage peak is observed. In addition, differential scanning calorimetric (DSC) illustrated that the produced fine AP samples in exothermic decomposition has an intermediate peak that has a high overlay with low temperature decomposition (LTD) and high temperature decomposition (HTD) peak. In general, decomposition of produced sample showed one exothermic peaks.

In this study, a new simple model is proposed for predicting the thermal decomposition temperature of energetic nitroaromatic compounds. The results show that the elemental composition and several structural parameters have major effects on this model which is derived by multiple Linear Regression (MLR) approach. The determination coefficient of the model is 0. 940 for 29 compounds as training set. Furtheremore, the root mean square and absolute standard deviation of the proposed model are 9. 90 and 8. 44, respectively. The decomposition temperature of 7 energetic nitroaromatic with various chemical structure as test set, are predicted by the new model. The results show the high predicting ability of the model. The validation of the proposed model is investigated through cross validation method. The value of Q2 LOO and Q2 LMO as 0. 943 and 0. 946, respectively confirmed good validation of the model. The proposed model can also be applied for the design of novel energetic nitroaromatic compounds having appropriate thermal stability.

The jet formation caused by the collapse of a liner mainly depend on the characteristics of explosive loaded in the shaped charge warhead. The aim of this study was to compare the influence of Octol and PBXN-110 fillers on the performance of a specific shaped charge warhead is made. These materials are loaded into the aluminum-cased shaped charge having a 35° copper liner and 510 cm3 of capacity. Obtained results by numerical simulation (LS-Dyna) indicated that the most effective stand-off is 50 cm. Based on simulation data, octol has a higher penetration compared to PBXN-110 for the same stand-off. Results from the experimental tests also showed that the warheads loaded with octol and PBXN-110 have penetration about 444 mm and 324 mm respectively. PBXN-110 exhibited a weak penetration effect due to its lower density and detonation velocity compared to Octol.

One of the regular tests used for the design of explosive materials for internal explosion is doing the explosion in a closed or partially closed environment to detect and analyzing the blast wave parameters. To this mean, researchers carry out the test, so-called two-room test. The test is performed in two reinforced concrete-built rooms which are connected by a door. The explosive material is detonated in one room and its effects are measured and analyzed in both room. The purpose of the current study is to predict the maximum number of explosions which leads to destruction of the prefabricated rooms. Hence, after validation of the solution, the numerical simulation of the successive explosions was performed by AUTODYN hydrodynamic software. The damage parameter in RHT model of concrete was used as a basis to determine the number of allowable explosions. According to the mentioned basis and with extrapolating the simulation results, maximum number of the allowable explosions was determined for different amount of explosives.

The effect of the presence of compounds such as H2O, NH3, UDMH and NH2-NH2 on the inter-molecular proton transfer of 3-Nitro-1, 2, 4-triazole (NTO) has been reported using quantum mechanic calculation. Gaussian 09 program has been used to calculate geometry optimization and all reactions with 6-311++G(d, p) basis set. In these studies, the substances mentioned in the molecular reactions act as a catalyst. The results have shown that in NTO an intramolecular proton transfer occurs in the presence of the above catalysts, and the NTO keton form transform to its enol state. According to the calculations, in the absence of the above materials and in environmental conditions, the amount of energy needed for this conversion is approximately 205. 65 kJ / mol. This amount of energy indicates the sustainability of the primary material. Using quantum mechanical calculations, the amount of activation energy required to the inter-molecular transfer of proton in the presence of water, ammonia, hydrazine, and asymmetric dimethylhydrazine compounds was calculated 70. 44, 56. 64, 64. 56, and 57. 02 kJ/mole respectively.

Among the burning rate accelerating catalysts, liquid ferrocene derivatives have been used extensively due to their proper performance and suitable processability. However, these compounds start to migrate during the retention time which lead to destructive changes in propellant performance and more sensibility to undesired stimulations. In order to avoid these problems, researchers have tried to graft them to HTPB prepolymer. Butacene is an attractive example of such compounds. In this study, the synthesis of novel propacene burning rate accelerating catalyst has been performed by changing the chain length of ferrocene derivative and modification of iron percentage. Physical characteristics like density, viscosity, hydroxyl amount and thermal properties of the product have been investigated. The results of our experiments showed that propacene is a better candidate due to its more suitable properties such as significant low viscosity and much better thermal stability in comparison to butacene.