فصلنامه مواد پر انرژی
سال دوازدهم شماره 2 (پیاپی 34، تابستان 1396)

PBXN-109EB is a new plastic bonded explosive containing energetic binder system NHTPB NPB, RDX and Aluminum that has better performance and energetic properties than PBXN-109 with inert binder system. In this work, at first, morphology of PBXN-109EB was investigated by Scanning Electron Microscopy (SEM) and then thermal behavior and its kinetic parameters of thermal decomposition were extracted via kissinger method by Differential Scanning Calorimetery (DSC) technique in various heating rates. After wards, some of the safety tests for insensitive munitions (such as fast cook off, inductive explosion, bullet impact and fragment impact tests) were performed on the sample and approved its insensitivity. Moreover, lead block (trauzl) and dent tests for comparison betweenexplosion power of PBXN-109EB with PBXN-109 were performed. Results showed that the explosion power of PBXN-109EB enhanced 13 % and 33 % related to PBXN-109 based on trauzl test and dent test, respectively.

In this research, three dimensional transient simulations of explosion shockwaves have been performed by using computational fluid dynamics (CFD). For this purpose, the characteristics of explosive mass and the geometry of explosion environment have been imported to Ansys Fluent CFD software. The simulation results have been validated by using experimental data obtained from literature. The comparisons between computational and experimental results show that CFD is a versatile means to predict the characteristics of explosion shockwaves. Afterwards, the effects of different parameters on explosion shockwaves have been investigated. These parameters are the distance of explosive from barrier, barrier height, explosion energy, explosion energy release time and the absence of barrier.

Strontium nitrate as a strong oxidizing agent in the formulation of pyrotechnics, reacts with fuel and produces red light. The factors which may affect the particle size of strontium nitrate have been optimized using Taguchi method. These factors include strontium nitrate concentration, type of non-solvent, addition method of solvent to non-solvent, modifier type and modifier ratio, all considered at double levels. The ANOVA showed that 85 % (w/w) as Sr(NO3)2 concentration, methanol as type of non-solvent, temperature at 5 oC, spraying as addition method, modifier type of MEK and modifier ratio 1:4 are optimal conditions for the production of Sr(NO3)2 nanoparticles. The average particle size of produced Sr(NO3)2 is about 38 nm.

Polyurethane- ureas are one of the polyurethane categories that exhibit better phase separation due to increasing the hard segment length and higher strength due to presence of three-dimension non-covalent interactions specially hydrogen boding. In this research, hydroxyl-terminated polybutadiene based polyurethane-ureas network have been synthesized via one-pot polymerization of triethanol amine triflouroborate comlex as cross-linker, isophoron diisocyanate as curing agent and variable values of 4,4`- bis (phenyl amine) methane as chain-extender and their mechanical and thermal properties have been investigated and compared to same polyurethane sample with no chain extender. The results revealed that chain-extender insertion in polyurethane-ureas structure led to decreasing in samples mechanical propertie in contrast to previous reported results. In addition, samples exhibit more viscous behavior in room temperature, too. Moreover, chainextender content increasing caused higher mechanical properties due to intensifying non-covalent interaction between polymer hard segments. Samples chemical structure characterized by FT-IR and their mechanical and thermal properties investigated by Tensile and Dynamical- Mechanical Analysis respectively.

In this work, thermal degradation behavior of a solid composite propellant containing Epoxy/Ammonium perchlorate\Strontium nitrate\Anthracene was studied by simultaneous thrmogravimetric analysis and differential scanning calorimetry under dynamic nitrogen atmosphere at different heating rates. Variation curves of the thermal degradation activation energy of Epoxy\Ammonium perchlorate\Strontium nitrate, Epoxy\Ammonium perchlorate\Anthracene and Epoxy\Ammonium perchlorate\Strontium nitrate\Anthracene calculated were evaluated by differential and integral isoconversional methods and AKTS software package. Self-accelerating decomposition temperature and explosion critical temperature of the composites has been determined to evaluate their thermal stability. Thermal degradation activation energy and pre-exponential factor of the composites were determined by Kissinger method. Finally, life-time prediction of the composites was done by AKTS software.

Dissolved hexamine in acetic acid is used as precursor in production of HMX explosive by Beckmann procedure. But, the gradual degradation of hexamine is occurred in acidic media, leading to decrease of purity and efficiency of HMX. In this research, the kinetic of degradation reaction of hexamine is studied in acetic acid media. The concentration of formaldehyde as product of degradation reaction of hexamine is measured by spectrophotometric method. The pseudo first order constants of degradation reaction are determined at 25, 35 and 45 oC. The activation energy of degradation reaction of hexamine is obtained 32.2 kJ/mol by Arrhenius equation. The obtained results showed degradation 5% for dissolved hexamine in acetic acid at conditions of initial concentration of 38% W/W, time of 34 h and temperature of 45 oC. The efficiency of HMX production in Beckman procedure is obtained as 49.0 and 31.5%, respectively, for fresh and aged hexamine solution after 30 days. The impurity of RDX as a by-product is increased from 11 to 35% with aging of hexamine solution.

The binder is an essential ingredient of solid composite propellants. Today, the industrial military scientists have been focused on finding and developing the new energetic binders to enhance the performance of composite propellants. In this research, triblock hydroxyl-terminated polybutadiene (HTPB) with Glycidyl azide polymer (GAP) was synthesized as a new energetic binder. In the first step, PECH-PB-PECH copolymer was synthesized from the reaction of epichlorohydrin (ECH) with HTPB as a macro initiator in the presence of boron trifluoride etherate as catalyst; which then was characterized by FTIR, 1H-NMR spectroscopies. In the second step, the GAP-PB-GAP copolymer was synthesized by azidation of the triblock polyepichlorohydrin (PECH) and HTPB in the presence of sodium azide and mixed solvents of dimethyl acetamide and toluene at 70OC (90% yield). The effects of monomer, catalyst, and solvents on molecular weight, as well as the yield of copolymer (GAP-PB-GAP) were studied. The synthesized copolymers were identified by IR, NMR, GPC, DSC, TGA, viscosity and TLC (tin layer chromatography) methods. In addition, after finding the curing conditions, the mechanical properties of polyurethane-based GAP-PB-GAP (such as tensile strength and strain) were investigated.