فصلنامه مواد پر انرژی
سال سیزدهم شماره 4 (پیاپی 40، زمستان 1397)

In this work the relationship between impact sensitivity and electrostatic sensitivity of energetic nitro compounds is investigated. Also, the most important molecular descriptors which have effect on this correlation are studied. The results are shown that the ratio of number of the oxygen atoms to hydrogen atoms  ( nO/nH), the number of amino groups(NH2)have an important roles in the proposed model.  The determination coefficient of the new correlation is 0.99. Also, it has the root mean square deviation (RMSD) and the average absolute deviation (AAD) of 2.79 and 2.09 J, respectively. In addition, the correlation gives good predictions for further 14 energetic nitro compounds as test set. Currently exact mechanism of initiation of energetic materials due to external stimuli is not well understood. We tried to investigate the relationship between impact sensitivity and electrostatic sensitivity of Nitro Energetic Compounds, and recognize the effect of structural factors in the development of this sensitivity using Multiple Linear Regression Method. The proposed model can also apply for designing novel energetic nitro compounds.

Effect of temperature and curing agent type parameters on rheological behavior of binder system based on Hydroxyl terminated Polybutadiene (HTPB) is important in the aspect of production for medium and large-size grains. In this research, the effect of casting temperature 40, 50 and 60 ºC) and chemical structure of curing agents (TDI, IPDI and HDI) on rheological behavior of a binder system based on HTPB were investigated. Increasing casting temperature due to curing progress, builds up the viscosity. Therefore, decreasing casting temperature by controlling curing process increases the pot life of binder system. logarithmic variation of viscosity versus time for three binder systems based on TDI, IPDI and HDI at different temperatures implies that binder system based on HTPB-TDI due to aromatic structure of TDI shows the fastest viscosity build up.Moreover binder system based on HTPB-IPDI shows lowest viscosity build up due to aliphatic structure of IPDI.

Binder has a key role in the performance of composite propellants. The binders are classified into two neutral and high-energy categories. GAP is one of the most important energetic binders, but it has poor mechanical and thermal properties. The goal of this investigation is to improve the properties of GAP by copolymerizing it with polytetrahydrofuran. New energy triblock copolymer was synthesized using 1,4-Butanediol as a initiator and cation ring polymerization method using epichlorohydrin and tetrahydrofuran monomer in the presence of Boron trifluoride as a catalyst. The triblock copolymer w::as char::acterized using GPC, 13CNMR, ˡHNMR, IR. The thermal behavior of the synthesized polymer has been investigated using DSC-TGA, which results showed increasing the thermal stability and reducing the glass transition of the copolymer compared to GAP. Effects of three energetic plasticizers on viscosity and Tg of copolymer was studied. In addition, elastomers base on tri-block copolymer was synthesized using IPDI and N100 as curing agents and mechanical properties of these were analyzed.

For reducing the structural damage against blast loading, fiber reinforced polymers sheet (CFRP, GFRP) can be used for retrofitting the RC slabs. In this study specimens of reinforced concrete slabs with or without retrofitting are modeled numerically. The results show that the using of high resistant, elastic material such as FRP sheets, are effective in reducing the deformation of the slabs, but it doesn’t significantly increase the energy absorption capacity of the structure. Using Polyurea (PU) coating with elastoplastic behavior on the FRP sheets, in addition to reduce deformation, it will increase the absorption of energy up to 40 percent. In this combination, layer arrangement is important matter, so that if the PU coating positioned on the concrete then the hard sheets are placed, its efficiency will be reduced by 30% compared the previous one. When the reinforcement element placed in front of the slab, it will increase the energy absorption up to 50 percent compared to the placing in the back of the slab. It has been shown in this study that it is not advisable to use PU alone and it should be used with stiffeners for better results.

In this study, the rheological parameters such as yield stress, viscosity coefficient, and power law index were obtained for double-base propellants and modified double-base propellants formulations using the Squeeze flow rheometric method. Squeeze flow test was used to investigate the rheological behavior without wall slip condition, and to determine the temperature dependency of fluidity in double-base propellants and modified double-base propellants formulations. The results showed that for double-base propellants and modified double-base propellants formulations, the initial elastic behavior is identical in terms of phenomenology, however, differs in term of the value. There are distinct structural differences and different rheological properties between double-base propellants and modified double-base propellants formulations. By increasing the percentage of energetics nitramines (RDX) in modified double-base, the average squeeze flow force moves to higher values. A similar behavior is observed by decreasing the percentage of nitroglycerin. The results show that the Sherwood’s model for the flow of double-base propellants is better than the curves of modified double-base propellants, which reflects the deviation of the rheological behavior of modified double-base propellants from Herschel-Bulkley fluids.

Glycidyl azide polymer (GAP) is used as a binder in the propellants. Energetic ionic liquids are used as a plasticizer to correct the properties of polymer. In this study, first ionic liquid was bonded to the GAP by certain amount and then the energetic anions of nitrate (NO3) and azide (N3) were used to exchange anion. FTIR analyses confirm accurately anions exchange. DSC, viscometer and heat of combustion analyses have been done. The glass transition temperature, viscosity and GAP energy were changed by anion exchange. Glass transition temperatures for ionic liquids with nitrate (NO3) and azide (N3) anions were measured -43.25 °C and -40.91 °C, viscosities 4 Pa.s and 5 Pa.s and heats of combustion 20.46 kJ/g and 19.98 kJ/g, respectively. The results of the analysis indicate that the  ionic liquid with nitrate anion gives better results in comparison to the ionic liquid with azide anion.

In the present study, the heat of detonation of high energy compounds with CaHbNcOd  formula was obtained according to Kistiakowski-Wilson rules. Comparison of these results with experimental date, group additivity method and Kamlet method shows that the values of heat detonation based on the Kistiakowski-Wilson rules are more accurate. In the following, the values of detonation velocity and detonation pressure for some high energy compound were obtained by Kamlet method based on Kistiakowski-Wilson rules are obtained. The results show that the mean errors of this method in estimation of detonatin velocity and detonatin pressure are 5.27% and 10.7%, respectively. In order to increase the accuracy, the constants of Kamlet equations were modified by regressing the results to experimental values. The mean error of new equations in predicting the velocity and pressure of detonation are 3% and 3.97%, respectively, which have significantly improved compared to Kamlet equations.