فهرست مطالب سجاد دمیری

Flexible sheet explosive is a plastic bonded explosive (PBX) based on hydroxyl-terminated polybutadiene (HTPB), isophorone diisocyanate (IPDI) curing agent, cyclotrimethylenetrinitramine explosive (RDX), dioctyl adipate plasticizer (DOA) and diethylol dimethylhydantoin (DHE) bonding agent. In this research, the effect of polyethylene glycol-600 (PEG-600) chain extender additive compared to DHE bonding agent on some mechanical properties of product such as tensile strength and shore A hardness has been investigated. For this purpose, different formulations containing PEG-600 or DHE additives were prepared and various production conditions including different amounts of additives and the molar ratio of isocyanate to hydroxyl group were optimized and quality of samples were evaluated from the perspective of various mechanical and safety characteristics. Also, the completion of the polyurethane reaction and the presence of excess IPDI were monitored using the attenuated total reflectance infrared spectroscopy (ATR-IR) method. The final results in optimal conditions showed that by using of DHE or PEG-600 in the PBX formulation, the ultimate tensile strength and the yield strength of the material in the presence of two additives are close to each other and at least twice that of PBX without additive. Also, the shore A hardness is also decreases from 39 to 31 and 32, respectively. The additive-free material is a flexible elastomer with more plastic behavior, and by using chain extender or bonding agent, its stress-strain behavior approaches to semi-ductile mode. The results of this research can be used to replace the expensive substance of DHE with cheap, domestically produced PEG-600 polymer in the formulation of flexible sheet explosives.

In this study, some granulated and pressable formulations based on coating of pentaerythritol tetranitrate (PETN) explosives with high impact polystyrene polymer (HIPS), Viton fluoroelestomer and paraffin wax were developed. Thereafter, mechanical strength of pressed formulations and transition temperature of binders were evaluated using uniaxial compressive strength test and differential scanning calorimetric (DSC) method, respectively. Also, the effect of PETN particle size distribution on compressibility, mechanical strength, density and particle size of pressed samples based on HIPS binder were statistically studied and optimized using mixture design of experiments by Minitab software. In the optimized experimental conditions, the compressive strength and elastic modulus for PETN/HIPS mixture at ambient temperature and at the concentration of 4.0 wt.% of the binder, were 15.0 and 91.1 MPa, which is better than formulations based on expensive Viton polymer and paraffine wax. By using HIPS binder, increasing the amount of PETN particle size <150 μm, mechanical strength of pressed samples decrease, and also particle size distribution in the range of 150-300 μm , leads to production of better formulations.

Aging of a sheet explosive contain RDX explosive and HTPB binder is studied at temperatures of 50, 60 and 70 oC in times 60, 120 and 180 days. Dynamic-mechanical analysis (DMA), sol – gel analysis (SGA) and hardness measurements methods are used in this research.  The changes of tan_delta in DMA, hardness amounts and soluble fraction in SGA are measured for unaged and aged samples. The obtained results showed the samples are aged with increasing of temperature and time of aging process. The pseudo-first order kinetic equation and obtained data are used for calculation of kinetic rate constants of measured properties changes. The changes in tan_delta in DMA, hardness amounts and soluble fraction in SGA indicated kinetic rate constants, respectively, 0.9-2.3´10-3, 1.9-4.8´10-3 and 1.5-5.5´10-3 per day at temperatures of 50, 60 and 70 oC. The Arrhenius equation is used for calculation of activation energy of each changes and calculation of kinetic rate constants at temperature 25 oC. Kinetic rate constant at room temperature showed a reduction 50% in measured properties of the product after 3300 days (~9 years).

The oxidation – reduction reaction of trinitrotoluene (TNT) with potassium permanganate solution and its decolorination rate are used as a quality control test in industry to verify the purity of TNT. The impurities such as other derivatives of TNT are due to increasing decolorination rate of potassium permanganate solution. On the other, nitrotoluene sulfonates are usually formed when sodium sulfite is added to TNT. The presence of sodium and sulfur in the TNT bulk is confirmed by using ICP technique. In this research, the kinetic of potassium permanganate reaction with pure TNT and nitrotoluene sulfonates (TNT and sodium sulfite) is studied using the absorption spectrometry in visible region and the rate constants and the reproducibility of the method are measured for determination of nitrotoluene sulfonates amounts. In the optimized concentrations of sulfuric acid (0.6 M) and potassium permanganate (0.6 mM), the results show 1.3 times increasing of reaction rate in the presence of nitrotoluene sulfonate. Introducing a simple, inexpensive and rapid method for quantifying nitrotoluene sulfonates are the advantages of the proposed method.

In this research, with evaluation of the solubility of cyclotetramethylene tetranitramine (HMX) explosive in different concentrations of water- methyl ethyl ketone (MEK) solvent, at a temperature range of 40-70 °C, the solubility and some thermodynamic parameters such as enthalpy of dissolution and mixing were calculated. Thereafter, in order to increase the capacity of the crystallization process, the effect of digestion of HMX in evaporative crystallization procedure on the morphology and polymorph conversion of crude HMX was investigated using electron microscopy, X-ray diffraction (XRD) and Raman spectroscopy. Then, two quantitative methods based on the XRD and Raman spectroscopy were developed for the determination of -HMX in  -type samples. The results showed that with the mentioned methods, -polymorph can be determined in the linear dynamic range of 0.32-5.25 wt. % in  -HMX. Also, the crystallization studies in MEK using digestion and evaporative crystallization showed complete conversion of crude HMX polymorphs to  -type, along with significant increasing in the crystallization capacity.