Showing 8 results for Thermal Stability
Dr Hassan Rezaei Haghighat, Dr Mehdi Barikani, Dr Jalil Morshedian,
Volume 8, Issue 2 (12-2013)
Abstract
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 multi-modal molar mass distribution of the product was elucidated by reductive hydrolyzation of the oligomeric product. The new polyfunctional hydroxyl-terminated polybutadiene (PFHTPB) was characterized and used in preparation of an HTPB-based polyurethane. The effects of this new hydroxyl-terminated polybutadiene on mechanical properties and thermal stability of its corresponding polyurethane elastomer were studied. The mechanical and thermal stability characterization of the elastomer were evaluated by tensile and TGA tests. Due to an efficient increase in crosslink density of the PFHTPB-based polyurethane elastomer, a significant enhancement in mechanical properties (more than 2.5 fold in tensile strength with small increase in elongation at break) was achieved. Furthermore the thermal stability of PFHTPB-based PU was comparable with its corresponding HTPB-based polyurethane elastomer.
A Mollaei, M. R Rahimipoor, M. A Dehnavi,
Volume 10, Issue 3 (1-2016)
Abstract
Aluminum powder is a common ingredient in energetic materials. Reactivity of this metal can be improved by reducing the particle size, due to their larger surface/volume ratio. In this research, the effects of using nano-structured aluminum powder investigated on physical, thermal, mechanical and explosive characteristics of an HMX-based PBX. The results indicated that the experimental density increased up to 2.5 percent by replacement of the nano-structured aluminum powder instead of micronized aluminum. It has also shown that this replacement caused to the hardness and tensile stress enhanced to 18 Shore D and 0.67 MPa, respectively. On the other hand, the elongation at maximum stress decreased from 10.5 to 9.8 percent. Furthermore, a catalytic effect has been shown in phase transition and self-decomposition temperatures of HMX in DSC analysis. This catalytic effect increased the impact sensitivity of composition up to 7.7 percent. Based on comparative dent test, it is established that the nano-structured aluminum powder has no considerable effect on detonation characteristics of PBX charge.
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Volume 12, Issue 1 (7-2017)
Abstract
C4 composition is a conventional military explosive formulation based on cyclotrimethylenetrinitramine explosive (RDX) and polyisobutylene binder (PIB), which some environmental factors such as thermal and oxygen lead to change in its color and physical characteristics. Using anti-oxidant to reduce the impact of environmental factors and increasing the stability of materials such as C4 during their storage and applications is the very useful. In this research, the effect of different concentrations of Irganox 1010 antioxidant on thermal degradation and stability of PIB and C4 at different temperatures was investigated using ultraviolet-visible (UV-Vis.) absorption spectroscopy, colorimetric histograms, thermal analysis and attenuated total reflection (ATR) infrared spectroscopy techniques, then the quality, absorption and color of the materials were studied quantitatively. Also, the necessary kinetic analyses were evaluated by Arrhenius method to estimate the rate constants and activation energies (Ea) of the thermal degradation reactions, from accelerated aging results on C4 and PIB at different temperatures. The results show that presence of antioxidant in the mentioned materials leads to 2-3 times reduction in the degradation and color change kinetics, and also increasing of activation energy of reactions. In the presence of 0.4 wt. % antioxidant, activation energies are increased from 67.4 to 97.8 kJ/mol for PIB, and from 117.88 to 136.80 kJ.mol for C4. Moreover, the chemical lifetime of C4 based on the color change, predicted using Vant-Hoff equation, in the temperature of 80.0 °C and the presence of 0.4 wt. % antioxidant, are changed from 1.3 to 25.0 years.
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Volume 12, Issue 1 (7-2017)
Abstract
One way to thermal stability and ablation improving of polyurethane elastomers with approach of solid propellant rocket insulation, is use of fillers such as silica particles with property of high ablation. In this study, it was paid to prepare polyurethane-silica composites (16,25 and 38% by weight) and polyurethane-silica nanocomposites (10, 16 and 25% by weight) and then interaction, morphology and thermal stability of them has been investigated by using of Fourier transform infrared spectroscopy (FTIR & ATR), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). Infrared spectra are confirm the formation of polyurethane and SEM images also show the proper distribution of the silica particles in the matris of polyurethane. TGA results also show that the temprature of 50 percent weight loss, due to function of silica particles as char trap, is increased that this result was approved by using of corrected thermal gravimetry method. The amount of residual mass of polyurethane composite containing 25 wt% silica was about 0.72 wt.% while this amount for the nanocomposite with the same amount of silica particles was equal to 1.8 wt.%.
Mohammad Reza Nayeb Hosseini, Mohammad Ferdowsi,
Volume 12, Issue 4 (3-2018)
Abstract
Chemical stability in propellants is important issue. In this article chemical and thermal stability for two kinds of double and single base propellants are investigated. In mass loss test in 90 0C, after 18 days mass loss for both samples is no more than 3%. By stabilizer measurement it was evident that remaining stabilizer content in aged samples are more than 10% in relative to fresh samples. Also kinetic calculation results from Differential Scanning Calorimetry (DSC) Shown no obvious changes for heat of reaction and kinetic parameters. In vacuum stability test, All samples except double base propellant which was aged in 90 °C released less gas volume in relative to standard. Also released gas from this sample are identified by ion mobile spectrometry it was evident that main composition of released gas is nitrogen oxides. Releasing NOX gases indicated that this sample is in autocatalytic State.
Manoochehr Fathollahi, Fatemeh Hemmati Khorasanloo, Habibeh Lotfzadeh,, Seyed Ghorban Hosseini,
Volume 15, Issue 3 (5-2020)
Abstract
HMX and PETN explosives are the most important and usable explosives in the military and defense industries and possess wide range of applications for military as well as commercial applications. Numerous difficulties are encountered during the processing, conveying and storage of powders which are all attributed to their electrostatic charging. Indeed, charged powders could cause damage ranging from losses in quality and productivity to more severe accidents like explosions. In this study, paraffin / [H.mim][Cl] ionic liquid and paraffin/ lecithin were added to HMX and PETN explosives. Then they were studied by the powder volumetric resistivity test and electrostatic charging test setup. The accumulation of static charge was also measured. The samples were evaluated for further studies in the terms of mixing quality by FE-SEM and EDX analysis. In this work, the amount of reduction in static charge was considerably improved in the HMX and PETN samples, containing paraffin and lecithin was 56.67% and 66%, respectively and thermal stability was 25.15% and 36.15%, respectively. Adding ionic liquid with paraffin to HMX and PETN explosives, the amount of reduction in static charge was significant and was about 106.66% and 100%, respectively.
Dr. Mohammadali Zarei, Maryam Elham, Dr. Minoo Sadri,
Volume 16, Issue 2 (12-2020)
Abstract
Today, the need for high-energetic materials with high thermal stability is felt in various military and civilian industries. Melamine-based compounds have attracted the attention of researchers in this field since many years ago, with various characteristics, including a nitrogen-rich structure with intra- and intermolecular hydrogen bonds.The use of melamine structure and its salts in the formulation of solid composite propellants in different roles improves their functional properties. In addition, recently, the synthesis of several high-energetic salt based on the melamine dioxide molecule was an effective step towards the development of a new generation of high-energetic materials; These new salts are in the form of structures with intramolecular fuel and oxidizer; and the investigations show that three monoanionic salts (MDOP, MDOMN and MDONA) with having detonation velocities in the range of 8711-9085 (m.s-1) are comparable to the conventional compound RDX, while the sensitivies to impact (IS: 23-27 J) and friction (FS: >240 J) in these salts are much lower than RDX, HMX and AP.
Seied Mahdi Pourmortazavi, Seied Mahdi Pourmortazavi, Saeed Tavangar, Manoochehr Fathollah,
Volume 19, Issue 4 (12-2024)
Abstract
In this research, composites of Al/RDX as energetic formulation were prepared using aluminum particles as metallic fuel and RDX as an explosive. SEM/EDX/MAP and FTIR analysis were used to characterize and explore the quality of the prepared composites, while thermal analysis was used to determine their thermal behavior. The results showed that by the increase in the amount of RDX in the formulation, the decomposition temperature of RDX towards higher temperatures. Also, the thermokinetics and thermodynamics parameters, as well as the critical explosion temperature and the self-igniting decomposition temperature of the composites were investigated by two methods, i.e., Kessinger and Starink. The results of the calculations showed that the activation energy has increased from 277 kJ/mol to 400 kJ/mol by decreasing the percentage of Al in the formulation. On the other hand, the enthalpy and entropy of the activation also show an increase, which indicates the effect of Al powder in Al/RDX composite formulation
