فصلنامه مواد پر انرژی
سال دهم شماره 1 (پیاپی 25، بهار 1394)

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 formulation. The weight ratio of soft segments GAP/PPG in polyurethane samples is changed as following order: 0:100, 30:70 and 50:50. For the study the structure – property relationships 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 results of polyurethane samples 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 GAP extent of 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 hydroxy 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 by 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 nonahydrate (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 varies from 20 to 30 nm and their lengths from 5 to 10 μm. Phase study by X-ray Diffraction Spectroscopy (XRD), the obtained bonds via two methods of Fourier Transform Infrared Spectroscopy (FT-IR) and Raman Spectroscopy, and also 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 °C and 83.5 °C 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 armours 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, composition based on HTPB having different amount of aluminum (0 up to 40 percent by weight) was examined in a specific shape charge. Total weight of explosive was about 30 g. Shaped charges of 40 mm calibers were prepared and penetration experiments were carried out at 25 mm stand-off distance on mild steel targets. The results established high penetration capability of aluminum-free formulation. Penetration resulted by this charge has a 61 mm depth and 4.4 cm3 volume. There is a nonlinear decrease in the penetration of the shaped charges by adding aluminum in formulation of explosives.

4, 10- Dinitro-2, 6, 8, 12- tetraoxa-4, 10- diazaisowurtzitane (TEX) is well known as an efficient Insensitive high explosive. It was usually prepared via nitration of 1, 4- diformyl- 2, 3, 5, 6- tetrahydroxy piperazine reaction using a mixture of fuming nitricacid and concentrated sulfuric acid. However, these traditional liquid acids are toxic, corrosive and produce 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 yields of ionic liquids, the ionic liquid, the amount of nitric acid, reaction temperature and reaction time have been studied. TEX was characterized by nuclear magnetic resonance spectra (NMR) and Fourier transform infrared (FTIR).

Illumination flares from the past to the present have been used in order to create light and signal in critical conditions. Flare formulation consists of three components i. e., fuel (magnesium) and oxidants (sodium nitrate) and a binder. Performance of illumination flares depend on many parameters such as ratio of oxidizer to fuel, particle size of fuel, binder type and binder weight percent. In this research work, the impact of a change in the type of binder was examined at the first step and then and the effects of ratio oxidant to fuel on light intensity and illumination efficiency were studied. Finally, thermal analysis (DSC) and (TG) data was used to calculate reaction model, kinetic and thermodynamic parameters. Then the relationship between the performance and activation energy was determined.