Koshun Iha

Adsorption of di-2-pyridyl ketone salicyloylhydrazone on Amberlite XAD-2 and XAD-7 resins: characteristics and isotherms.

The adsorption of DPKSH onto Amberlite XAD-2 (styrene resin) and XAD-7 (acrylic ester resin) has been investigated, at (25+/-1) degrees C and pH 4.7. The experimental equilibrium data were fitted to the Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) models. These three models provide a very good fit for both resins and the respective constants KL, KF, and KDR were calculated. For the same DPKSH concentration interval, the minimum time of contact for adsorption maximum at XAD-7 was smaller than at XAD-2 and the maximum amount of DPKSH adsorbed per gram of XAD-2 is smaller than at XAD-7. The investigation indicates that the mean sorption energy (E) characterizes a physical adsorption and the surfaces of both resins are energetically heterogeneous. The constants obtained in these studied systems were correlated and compared with those obtained for the silica gel/DPKSH system.

Influence of the Heating Rate in the Thermal Decomposition of HMX

This work refers to a study of the thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7 tetrazocine (HMX) by differential scanning calorimetry (DSC) in non-isothermal conditions, with heating rates from1 to 25°C min−1. The influence of the heating rate, the particle and the sample size were verified. The activation energy was calculated using the peak temperature shift method, proposed by Ozawa and a significant variation in the results was observed according to the range of the used heating rates. As the heating rate was increased, different conversions and self-heating effects were observed at the respective DSC peaks, indicating that the use of this method was inadequate and it may lead to incorrect results, which, in turn, could explain the wide range of activation energy values published in literature. At lower heating rates HMX decomposition occurs on the solid state and at higher ones decomposition occurs after melting practically at the same temperature, which does not depend on the heating rate.

Evaluation of weather influence on mechanical and viscoelastic properties of polyetherimide/carbon fiber composites

In order to investigate how environmental degradation affects the mechanical and thermal performance of polyetherimide/carbon fiber laminates, in this work different weathering were conducted. Additionally, dynamic mechanical analysis, interlaminar shear strength tests and non-destructive inspections were performed on this composite before and after being submitted to hygrothermal, UV radiation and thermal shock weathering. According to our results, hygrothermally aged samples had their glass transition temperature and elastic and storage moduli reduced by plasticization effect. Photooxidation, due to UV radiation exposure, occurred only on the surface of the laminates. Thermal shock induced a reversible stress on the composite’s interface region. The results revealed that the mechanical behavior can vary during weather exposure but since this variation is only subtle, this thermoplastic laminate can be considered for high-performance applications, such as aerospace.

Gaseous Oxygen Injection Effects in Hybrid Labscale Rocket Motor Operations

4Hybrid rocket motor features such as operational safety, thrust tailoring, low investment cost and constructive simplicity are currently widespread. Nevertheless, inefficient combustion reduced mass fraction and mostly low regression rates still play a role in the major disadvantages. Swirling oxidizer flow is known to affect the mixing between oxidizer and fuel, intensifying heat exchange thus increasing regression rate. A laboratory scale hybrid engine was developed, and tests were conducted with gaseous oxygen (GOX) supply, ultra high molecular weight (UHMW) polyethylene, one axial and two swirl injector types. Oxygen mass flow, grain length and diameter and test time were maintained constant in order to evaluate the GOX injection influence on the motor performance and combustion characteristics. Series of six tests for each injector were performed with one unique set of machined throat diameters, to acquire a range of oxidizer mass flux for comparison. The data of oxidizer mass and fuel consumption were collected, and average regression rate values were calculated. Empirical correlations for the regression rate coefficients were obtained for each injection method. The burn grain profiles were analyzed and compared, sustaining that the income oxidizer flow pattern strongly affects the regression rates.

Síntese e caracterização do polímero energético Metil Azoteto de Glicidila (GAP) via análises instrumentais

To obtain more energetic, safe propellants, with improved performance, better mechanical properties and low cost, new materials have been researched and tested. One of these materials is Methyl Glycidyl Azide Polymer (GAP). It can be used to make energetic and/or smokeless propellants as well as composite explosives with low sensitivity. GAP was synthesized and characterized by FT-IR, elemental analysis, gel permeation chromatography (GPC) and thermal analysis.

Thermal degradation and lifetime estimation of poly(ether imide)/carbon fiber composites:

The thermal decomposition behavior of poly(ether imide) (PEI)/carbon fiber composites used in aeronautical field was studied using thermogravimetric analysis in an inert atmosphere, at several heating rates between 2 and 10°C min−1. The activation energies (E a) were determined by Flynn–Wall–Ozawa (FWO) and Kissinger methods, and the preexponential factor (A) was calculated by the FWO method. The obtained data were used in order to predict the thermal lifetime of the material under the established temperature range and 5% mass loss criterion. Overall, the results represented PEI’s good thermal stability. Furthermore, it was concluded that the material can be safely applied for aeronautical use.

Influence of water immersion and ultraviolet weathering on mechanical and viscoelastic properties of polyphenylene sulfide-carbon fiber composites

In order to investigate the combined action of temperature, humidity, and ultraviolet (UV) radiation, polyphenylene sulfide (PPS)–carbon fiber composite specimens were exposed to environmental degradation through two different techniques: water immersion and UV climatic chamber. The moisture weight gain curves of the composites were compared with those of the neat matrix in order to determine the interface effect on moisture absorption. Fourier-transform infrared spectroscopy of UV-weathered samples presented oxidation formation. Compressive tests and dynamic mechanical thermal analysis (DMA) revealed that the weathered materials gained in stiffness, nevertheless a small deterioration in strength was found after long periods of UV radiation exposure.

Design and Testing of a Hybrid Rocket Motor

This research aims to provide a methodology for the project of labscale hybrid motors. This development begun with the thermal analysis of the fuel grain using the Flynn, Wall and Ozawa method; this provided the simulation entry data to maximize the motor performance. The computer simulation was performed with the Chemical Equilibrium Specific Impulse Code of the U.S. Air Force, also known as ISP Code. Based on the optimum oxidizer to fuel ratio, the literature was used to supply the mathematical background for the calculation of the motor geometrical parameters whose operating conditions were determined throughout the simulation. Finally, firing tests were conducted to verify the reliability of the project methodology. The firing tests were performed with three injectors: 2 swirling and one axial. The tests showed that the higher the operation pressure the more suitable is the project, meaning the methodology developed works best in hybrid rocket motors with high operating pressures.

Estudo da decomposição térmica de propelente sólido compósito de baixa emissão de fumaça

The thermal decomposition of hydroxyl-terminated polybutadiene (HTPB)/ammonium nitrate (AN) based propellants, so called smokeless formulations, and raw materials were investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG). The thermoanalytical profile of different components and of propellant were evaluated and the Arrhenius parameters for the thermal decomposition of the propellant sample were determined by the Ozawa method. The kinetic parameters of the thermal decomposition of propellant samples were determined by DSC measurements. The values obtained for activation energy (Ea) and pre-exponential factor were 163 kJ mol-1 and 1.94x106 min-1.

Desenvolvimento de tecnologia de pré-polímeros na síntese de poliuretanos empregados em combustíveis sólidos

The aim of this work was to synthesize a polyurethane polymer matrix using polyols as a raw material to obtain a binder such as the hydroxyl terminated polybutadiene (HTPB) pre-polymer in energetic material formulation. The soybean-based polyol was the best starting raw material for producing a binder for solid fuel formulation in rocket motor applications. Characterization of the obtained soybean-based polyurethane binder was carried out by employing FT-IR analysis and thermo analytical techniques that showed similar HTPB binder thermo decomposition behaviors, confirming their potential for use as polymer matrix composites.