فصلنامه مواد پر انرژی
سال سیزدهم شماره 2 (پیاپی 38، تابستان 1397)

One of the problems for use of rubber in various industries is surface tension at the surface of rubbers, which results in the crack on the surface, fracture of the rubber and reduces its life. These tensions are caused by contacting the rubber component with the metal surface and the friction between two surfaces. Roughness of the surface, the composition of the rubber compound, the environmental factors, test conditions and etc. affect the friction between rubbers – metal. Surface roughness plays an important role in sliding between two surfaces and mainly controls friction behavior. On the other hand, roughness effect on the coefficient of friction is controllable using a suitable lubricant. Regarding the fuel consumption in the industry and the characteristics of self-lubricant of the most lubricants, in the present study, the effect of JP10 & Dmaz fuels as a lubricant was investigated to reduce the sliding friction coefficient between the NBR and aluminum surfaces with different roughness. Experimental studies showed friction coefficient has a good correlation with the mean surface roughness (Ra). By applying JP10 & Dmaz fuels as lubricant, the coefficient of friction decreased by about 65% & 85%, respectively.

Ammonium perchlorate (AP) is considered as a strong oxidizer in solid propellants. Therefore, its thermal decomposition characteristics directly influence the combustion behavior of solid propellants. The AP particle size, shape, and morphology influence on the thermal behavior. In this study, the solvent anti-solvent crystallization method equipped with an eductor mixer was used as a system for producing oxidizing materials for propellants. The eductor easily increases the quality of mixing and does not cost much to 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 weakened compared with the reference sample and the growth in (210) plane is greater than the 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. Also, differential scanning calorimetric (DSC) illustrated that the produced fine AP samples in exothermic decomposition has an intermediate peak. This peak 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 work the new simple model proposed for predicting the thermal decomposition temperature of energetic nitroaromatic compounds. The results are shown that the optimum elemental composition and several structural parameters have the most 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. Also, 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 have shown the high predicting power of the model. The validation of the proposed model is investigated through cross validation method. The value of Q2LOO and Q2LMO as 0.943 and 0.946, respectively confirmed that the good validation of the model.  The proposed model can also apply for designing novel ideal energetic nitroaromatic compounds with appropriate thermal stability.

The jet formation caused by the collapse of a liner is dependent mainly upon the explosive characteristics loaded in shaped charge warhead. In this study, the purpose was to compare the influence of Octol and PBXN-110 fillers on performance of a specific shaped charge warhead. This material loaded into the aluminum-cased shaped charge having a 35° copper  liner and 510 cm3 in capacity. Results obtained 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 exhibit a weak penetration effect due to its lower density and detonation velocity compared to Octol.

One of the regular tests used for designing explosive materials for internal explosion is doing the explosion in a closed or partially closed environment to detect and analyzing the blast wave parameters. In this regard, the test so-called two- room test is considered among researchers. 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 the effects of that are measured and analyzed in both of them. 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 has been reported on the inter-molecular proton transfer of 3-Nitro-1,2,4-triazole (NTO) using quantum computing. Gaussian 09 program package 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 down 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 into the presence of water, ammonia, hydrazine, and asymmetric dimethylhydrazine compounds was calculated 70.44, 56.64, 64.56, and 57.02 kJ/mole respectively.

Burning rate accelerating catalysts are reckoned to be of important additives in the synthesis process of composite solid propellants on which much effort is made these days to suggest a novel procedure for their synthesis. Among many tasted chemicals, liquid ferrocene derivatives have been used much more vastly due to their better performance and suitable processability. But, 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.
 According to the impotance of the produced polymers properties in synthesis process of solid propellant compounds, we have tried our best to synthesize the novel propacene burning rate accelerating catalyst by changing the chain length of ferrocene derivative grafted to the polymer and modifying the iron percentage. In the present study physical characteristics like density, viscosity, hydroxyl amount and the glass transition temperature of the product have been investigated. Iron content have also been determined by atomic absorption technique. The result of our experiments showed that propacene is better candidate due to its more suitable properties such as significant low viscosity and glass transition temprature and much better thermal resistance in comparison to butacene.