JOURNAL OF ENERGETIC MATERIALS
Year:2018 | Volume:13 | Issue:3 (39)|Papers Count:7

Binder has a key role in the performance of composite propellants. GAP is one of the most important energetic binders, however, it has not suitable mechanical and thermal properties, and Tg. The aim of this investigation is to improve the properties of GAP by its copolymerization with polycaprolactone. New energetic triblock copolymer was synthesized with a yield of 91% using glycidyl azide polymer (GAP) as a macroinitiator and following cation ring polymerization method using caprolactone monomer in the presence of dibutyltin dilaurate as catalyst. The synthesized PCL-GAP-PCL triblock copolymer was characterized using GPC, 13CNMR, ˡ HNMR, IR and its thermal behavior has been investigated using DSCTGA. The results show increasing of thermal stability and reduction of glass transition temperature of the synthesized copolymer compared to GAP.

Hydroxyl terminated polybutadiene (HTPB) is the most commonly used binder in composite solid propellants. However, due to its non-energetic characteristic, it is recognized as a dead weight in practice. Therefore, replacing HTPB with an energetic polymer is essential. In this research, nitrated hydroxyl terminated polybutadiene resin (NHTPB) with 12. 2% nitration rate, in combination with HTPB resin was used as binder. Thus, the HTPB propellant base formulation (HB) was prepared as a reference sample and its physical-mechanical properties, burning rate, and sensitivity were compared with two other cured formulations: the propellant formulation with binder ratio of 5% NHTPB and 95% HTPB (NH5) and the other with binder ratio of 10% NHTPB and 90% HTPB (NH 10). The results showed that, with increasing NHTPB to HTPB ratio from 5% to 10%, Young's modulus, burning rate, impact, and friction sensitivities were increased in comparison to reference propellant. In addition, the cross-linking density, hardness, and tension were decreased.

In this research, synthesis procedure of activated carbon (AC) was optimized from pistachio waste in order to maximize the COD (Chemical Oxygen Demand) removal from nitro hydroxyl-terminated polybutadiene (nitro-HTPB) resin production unit wastewater through a batch system. For this purpose, Response Surface Methodology (RSM) was applied to optimize the effective factors in AC synthesis preparation condition including impregnation ratio, carbonization temperature, and activation time. The optimal conditions for impregnation ratio by phosphoric acid, carbonization temperature, and activation time were 2. 76, 524. 34° C, and 38. 04 min, respectively. It was obtained that, the as-synthesized AC (in accordance with the proposed condition set) is able to remove 90% of COD. The study shows that the “ Freundlich isotherm” model was consistent with the results. Moreover, FT-IR and FESEM analysis were used to characterize bonds and surface morphology respectively.

Since Nanoparticles (NPs) tend to agglomerate, their catalytic activities decrease during propellant operation. Therefore, loading the nanoparticles onto the support is a general method to prevent the agglomeration and maintain the catalytic activities of the nanoparticles. Three dimensional (3D) graphene has high surface area and porous structure. Furthermore, 3D-graphene is an efficient support to grow and anchor NPs with high loading and better dispersity. In this study, firstly CuCr2O4 spinel NPs and CuCr2O4@3D-GFs nanocomposite were synthesized. Then, the structure and particles size were determined by XRD, FESEM and TGA. The as-prepared CuCr2O4 NPs and CuCr2O4@3D-GFs nanocomposite were used as a promising catalyst for the thermal decomposition of ammonium perchlorate (AP) and their catalytic performance was investigated by differential scanning calorimetry and thermal gravimetric analysis (DSC/TGA). Thermal decomposition of AP in the presence 4 wt % CuCr2O4 NPs and 2 and 4 wt % CuCr2O4@3D-GFs nanocomposite prepared by solventantisolvent method showed that two exothermic peaks of AP merges into one peak and high-temperature decomposition appeared at 348, 332 and 321° C, respectively.

Useing plasticizers in the formulation of solid propellants especially double-base solid propellants is inevitable. Double base propellants are composed of nitrocellulose (NC) polymer. Plasticizers increase flexibility and reduce viscosity and glass transition temperature. Energetic azido ester plasticizers are compatible with energetic binders in solid propellants. In this work, five different azido plasticizers as ethyleneglycol bisazidoacetate (EGBAA), trimethylene glycol bisazidoacetate (TMGAA), tetramethylene glycol bisazidoacetate (TMGBAA'), pentaerythritol tetrakis azidoacetate (PETKAA) and hyper-branched azidoester (HB-AZ) were successfully synthesized in two steps (formation of ester and azidation) with 55-92% yields. The synthesized azidoesters were identified by FT-IR and 1H-NMR spectroscopies. Study of the different parameters showed that pentaerythritol tetrakis azidoacetate and hyper-branched azidoester are more effective in reduction of the nitroglycerin migration than the other synthesized azidoesters.

In simulation and modeling of mass transfer phenomena, design of separation equipment; and predicting the mass transfer of miscible fuels, the mass transfer coefficients is required. In this study, a diaphragm-cell was manufactured to measure the liquid-liquid diffusion coefficient. The cell constant was obtained to be 0. 188 cm-2 with 0. 5 molar solution of potassium chloride solution. Based on this value, the binary diffusion coefficients of 0. 5 molar sodium chloride and heptane-benzene solutions were obtained as 1. 6×10-5 and 2. 38×10-5 cm-2/s at 25 ° C, respectively. These coefficients have been previously reported respectively as 1. 5×10-5 and 2. 29×10-5 cm2/s at 25 ° C. Afterward, the infinite dilution diffusion coefficients of heptane in benzene and benzene in heptane at 25 ° C were obtained as 3. 14×10-5 and 1. 88×10-5 cm2/s, respectively. These coefficients have also been previously reported as 3. 4×10-5 and 2. 10×10-5 cm-2/s respectively. The measured diffusion coefficients showed a good agreement with literature values. Finally, investigating the effect of liquid density of upper and lower part of the diaphragm cell on the measured value of diffusion coefficient showed that the solution with higher density should be charged in the lower part of the cell.

In this study, different flow analysis models in solid rocket motor are presented. Amongst these models, some are not capable of predicting the effects of significant phenomena such as erosive burning and longitudinal acceleration. In order to consider these effects on the internal ballistic, a quasi-one-dimensional model was developed which employs generalized flow equations. A non-viscous and incompressible quasi-one-dimensional flow with friction, mass injection and flow crosssection variation were taken into account in the governing equations. Then, assuming quasi unsteady flow and considering pressure drop and variation of nozzle throat diameter, and also neglecting the heat transfer in the walls, the governing equations were integrated along the engine length at each time increment. Finally, the flow characteristics inside the engine including the distribution of pressure, temperature, and Mach number along the engine as well as functional characteristics of the engine such as chamber pressure during the burning process were determined as a function of time. Erosive burning effects on the burning rate are of great importance at various conditions. Therefore, , the results of the model were compared with the experimental data of Saderholm model.