JOURNAL OF ENERGETIC MATERIALS
Year:2015 | Volume:10 | Issue:1 (25)|Papers Count:9

For improving the mechanical and thermal properties of polyurethanes based on glycidyl azide polymer (GAP), a series of polyurethane elastomers with two soft segments were prepared from hexamethylene diisocyanate (HDI/ GAP/PPG/TMP) and isophorone diisocyanate (IPDI/GAP/PPG/TMP). The weight ratio of soft segments GAP/PPG in polyurethane samples is changed as following order: 0:100, 30:70 and 50:50. For study the property of polyurethane samples, the average molecular weight between cross-link junctions and effective cross-link density (νe) of samples were calculated from swelling and dynamic mechanical analysis tests. Both tests have shown that, as the GAP contents of copolyurethane samples are increased, molecular weight between cross-links (Mc) is increased. also, dynamic mechanical analysis have shown that by increasing of GAP ratio in the soft segment of polyurethane, the storage modulus at elastic region decreased and the glass transition temperature (Tg) have increased. As well as, hardness of samples is measured and indicated that by increasing the amount of GAP in thef polyurethane samples, the migration of soft segment to the surface of polyurethane is improved and causes the dropping of the sample hardness.

In order to increasing of hydroxyl functionality of HTPB, an in-situ nitroxide mediated polymerization (NMP) of 1, 3-butadiene was carried out in presence of TEPA as a polyfunctional nitroxide precursor. The effects of this new hydroxyl-terminated polybutadiene on thermal and dynamic-mechanical properties of its corresponding polyurethane elastomer were studied via DSC and DMTA tests. A significant enhancement in crosslink density of the elastomeric product with small increase in glass transition temperature was achieved using PFHTPB. Also the absence of any endothermic peak in DSC thermogram was an indication of no crystalline domain existing in these samples.

In this study, the effect of copper chromite (CuO.Cr2O3) nanoparticles and multi-walled carbon nanotubes (MWCNTs) as nanocatalysts on the thermal decomposition behavior of ammonium perchlorate (AP) has been investigated using Differential Scanning Calorimetry (DSC). At first, copper chromite (CuO.Cr2O3) nanoparticles were prepared by inverse co-precipitation method. In this method, cupric nitrate trihydrate (Cu(NO3)2.3H2O), and chromium nitrate nona hydrate (Cr(NO3)3.9H2O) with a mole ratio of 1:2 were used. Then, multi-walled carbon nanotubes were modified by a chemical method.The MWCNTs were used with the average approximate diameter of nanotubes varying from 20 to 30 nm and their lengths from 5 to 10 mm. Phase was studied by X-ray Diffraction Spectroscopy (XRD) and the obtained bonds via two methods of Fourier Transform Infrared Spectroscopy (FT-IR) and Raman Spectroscopy. Microstructure observations and size of nanoparticles were determined by Field Emission Scanning Electron Microscopy (FE-SEM). The average crystallite size of obtained copper chromite was 18 nm. The results showed that using 3 wt.-% nano catalysts lowered the decomposition temperature of AP to 94.86 oC and 83.5 oC for copper chromite (CuO.Cr2O3) and nano- MWCNTs, respectively. Meanwhile, the total enthalpies, for these two cases, were 1132.31 J g -1 and 1308.71 J g -1 respectively.

Shaped charges defeat armors by means of high velocity jets formed by the collapse of a metallic liner as a result of the detonation of an explosive. The explosive formulation is an important factor influencing the properties of a shaped charge. Explosive charges used in penetrating devices have usually high detonation velocity and high density. In this research, five compositions based on HTPB having different amount of aluminum (0 up to 40 percent by weight) were examined in a specific shape charge. After charging the samples by PBX materials, the penetration experiments were carried out at 25 mm stand-off distance on mild steel targets. The results showed high penetration capability of aluminum-free formulation. The jet resulted by detonation of this charge has a maximum depth and volume of penetration in comparison with other PBXs. There is a nonlinear decrease in the penetration of the shaped charges by adding aluminum in the formulation of explosives. The difference of results obtained via experimental and numerical simulation method (LS-DYNA) increases in compositions containing more percentage of aluminum powder.

4, 10- Dinitro 2, 6, 8, 12, tetraoxa 4, 10- diazaisowurtzitane (TEX) is well known as an efficient insensitive high explosive. It is usually prepared via nitration of 1, 4- diformyl- 2, 3, 5, 6- tetrahydroxy piperazine using a mixture of fuming nitric acid and concentrated sulfuric acid. However, these traditional liquid acids are toxic, corrosive and produces hazardous waste. In addition, these acidic mixture cause product decomposition and low yields despite their high catalyst activity. In this research, the use of an efficient catalyst and mild reaction condition for TEX synthesis is reported for the first time. To access the high yield, the amounts of ionic liquid and nitric acid, reaction temperature and reaction time have been studied. The targeted compound (TEX) was characterized by nuclear magnetic resonance spectra (NMR) and Fourier Transform Infrared spectroscopy (FTIR).

Herein, the effect of type of binder was investigated firstly and then, the effect of proportional amount of oxidant to fuel on the light intensity and illumination efficiency and ignition temperature were studied. Finally, using thermal analysis (DSC end TG), reaction model was determined and kinetic and thermodynamic parameters were calculated. In the other hand, via heat of reaction (obtained from calorimetric bomb), the relationship between the performance and activation energy was determined. The results have shown that the heat of reaction is directly related to the amount of light and the activation energy do not have any proportionality with the performance.

In this paper, the plastic deformation of fully clamped circular plates is investigated, under different blast loadings by means of the ballistic pendulum. Experimental results are evaluated according to the mid-point deflection of the plate as well as the deformation profile. In order to assess the effects of materials mechanical properties on the plate deformation, some experimental tests are performed on various types of plates with different thicknesses, including copper, steel and aluminum. Furthermore, the effect of loading type on the plate deformation is studied through varying the charge stand-off distance. The numerical simulation is carried out using the finite element analysis software ABAQUS/EXPLICIT. In the numerical simulation, the results of calculating the pressure drop coefficient are compared, using two different methods. It should be mentioned that, for validating the numerical model, the yielded results of simulation are compared with experimental results. This comparison demonstrates that the numerical results have satisfying compatibility with experimental results. In general, regarding the presented equations, 74% and 67% of data are in the reliable range. Hence, utilizing the mentioned numerical model for predicting the deformation profile and also the mid-point deflection of circular plates is appropriate.