• Elastomers and Composites
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• v.51 no.2
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• pp.122-127
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• 2016

Thermal decomposition kinetics for two different types of polyurethane elastomers prepared with 2,2'-dichloro-4,4'-methylenedianiline (MOCA) and 3,5-dimethyl-thiotoluenediamine (Ethacure-300), based on PTMG/TDI isocyanate prepolymer, were studied using non-isothermal thermogravimetric analysis (TGA). Thermograms were obtained and analyzed using Friedman (FR) and Kissinger-Akahira-Sunose (KAS) methods for activation energy, $E_a$. The results obtained showed that decomposition reaction of both samples was observed similarly to occur through three different stages, i.e., initial stage with vaporization of low molecular weight materials, second stage of urethane linkage decompositions, and later stage of polyol segment decompositions. However, activation energy values at each stage for the sample cured with Ethacure-300 was much lower than those for the sample with MOCA, exhibiting relatively lower thermal stability for the sample with Ethacure-300 than that with MOCA.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.4
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• pp.63-65
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• 2008

The increased interest in reducing the environmental effects caused by releasing organic compounds and aqueous waste has motivated the development of polymeric materials in supercritical fluids. Recently, supercritical fluids have been used in material synthesis and processing because of their special properties, such as high diffusivity, low viscosity, and low surface tension. Supercritical carbon dioxide is the most attractive because it is non-toxic, non-flammable, and has moderate critical temperature and critical pressure values. Supercritical carbon dioxide can also swell most polymers. In this study, we prepared polymer/clay nanocomposites using supercritical fluids. Cloisites 10A, 15A, 25A, and 30B used in this study are montmorillonites modified with a quaternary ammonium salt. The nanocomposites of polymer/clay were characterized by X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry.

• Journal of the Korean Chemical Society
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• v.13 no.4
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• pp.309-312
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• 1969

A series of metal ion-2, 5-diamine 1, 4-dihydroxybenzene polymers containing copper(II), nickel(II) or cobalt (II) have been prepared. The structure was postulated on the basis of elementary analysis of polymers. It was found that copper polymer is most likely the coordination polymers by X-ray powder pattern studies. The thermal stability of the polymers was also studied by a simple method, utilizing a thermogravimetric balance. The order of thermal stabilities is Cu(II) > Ni(II) > Co(II). The polymers start to decompose at a relatively low temperature.

• Polymer(Korea)
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• v.38 no.5
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• pp.588-595
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• 2014

A semi-interpenetrating polymer network (semi-IPN) hydrogel composed of crosslinked chitosan and poly (acrylic acid-co-crotonic acid) was prepared in the presence of glutaraldehyde (GA) as a crosslinker. Fourier-transform infrared, thermogravimetric analysis and scanning electron microscopy were employed to confirm the structure of the semi-IPN hydrogel. The swelling capacity of hydrogel was shown to be affected by the monomers weight ratio, chitosan content, initiator and GA concentrations. The results also indicated that the semi-IPN hydrogel had different swelling capacity at various pHs. Additionally, the swelling behavior of the hydrogel was investigated in aqueous solutions of NaCl, $CaCl_2$, and $AlCl_3$.

• Journal of Environmental Science International
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• v.13 no.12
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• pp.1131-1138
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• 2004

The starch-filled waterborne acrylate (SWAC) films were prepared. The structures and properties of SWAC films were investigated by infrared spectroscopy, thermogravimetric analysis, and strength test. The biode­gradability of SWAC film was also studied by determination of reduced sugar products after enzymatic hydrolysis. The surface morphology of the SWAC film was investigated by scanning electron microscopy (SEM). The results showed that the tensile strength and elongation of SWAC film decreased with the increase of starch content. The SWAC film showed significantly higher water absorbed content than waterbonre acrylate film. The biodegradability of SWAC film increased as the content of starch increased. The biodegradation of starch in SWAC film by ${\alpha}-amylase\;was\;about\;77{\%}$ of that of pure starch.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.722-723
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• 2006

A new method has been developed to fabricate microcomponents by a combination of photolithography and sintering of metallic powder mixtures, without the need for compression and the addition of Mg. This involves (1) the fabrication of a micromould, (2) mould filling of the powder/binder mixture, (3) debinding and (3) sintering. The starting powdered materials consisted of a mixture of aluminium powder(average size of 2.5 um) and alloying elemental powder of Cu and Sn(less than 70nm), at appropriate proportions to achieve nominal compositions of Al-6wt%Cu, Al-6wt%Cu-3wt%Sn. This paper presents detailed investigation of debinding behaviour and microstructural development.

• Archives of Pharmacal Research
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• v.29 no.2
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• pp.178-182
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• 2006

Four crystal forms of cephradine were isolated by recrystallization and characterized by powder X-ray diffractometry, differential scanning calorimetry, and thermogravimetric analysis. The dissolution patterns of four crystal forms of cephradine were studied in water at $37{\pm}0.5^{\circ}C$, 90 rpm for 120 min. The amount dissolved at 120 min was highest for Form 1 ($100\%$), followed by Form 3 ($98.9\%$), Form 4 ($77.83\%$), and Form 2 ($75.55\%$). After storage for two months at $0\%$ RH (silica gel, $20^{\circ}C$), $52\%$ RH (saturated solution of $Na_{2}Cr_{2}O_{7}{\cdot}2H_{2}O/20^{\circ}C$), and $95\%$ RH (saturated solution of $Na_{2}HPO_{4}/20^{\circ}C$), none of the crystal forms showed transformation.

• Journal of Integrative Natural Science
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• v.1 no.2
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• pp.84-88
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• 2008

The formation and thermal properties of the $BaO_2$ and $TiO_2$ mixtures were prepared by mechanical alloying method was investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and thermogravimetric/differential thermal analysis (TG/DTA). The rotating speed of 750 rpm shows more effects on the formation of $BaTiO_3$ single phase. The internal strain calculated using Williamson-Hall method was $4.27{\times}10^{-3}$ for the mixture milled for 300 min, the crystallite size was calculated using the Scherrer method decreased with milling time. The $BaTiO_3$ crystal improved crystallinity was formed by thermal annealing at a temperature of $600^{\circ}C$ for 1 h for the mixture milled for 300 min.

• Elastomers and Composites
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• v.31 no.2
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• pp.122-129
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• 1996

The Thermal decomposition of the ${\alpha}-Cellulose$ and NaCl was studied using a thermal analysis technique in the steam of nitrogen gas with 30ml/min at various heating ranges from 4 to $20^{\circ}C/min$. The Derivative and Integral method used to be obtained values of activation energy of decomposition reaction. 1. The values of activation energy evaluated by Derivative and Intergral method were consistent with each other very well. 2. The maximum value of heat of decomposition evalated by DSC method was ${\alpha}-Cellulose/NaCl= 90/10$. 3. The thermogravimetric trace curve agreed with the theoretical equation.

• Carbon letters
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• v.16 no.1
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• pp.34-40
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• 2015

In this study, in order to improve the thermal and electrical properties of epoxy/graphene nanoplatelets (GNPs), surface modifications of GNPs are conducted using silane coupling agents. Three silane coupling agents, i.e. 2-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane (ETMOS), 3-glycidoxypropyltriethoxysilane (GPTS), and 3-glycidoxypropyltrimethoxysilane (GPTMS), were used. Among theses, GPTMS exhibits the best modification performance for fabricating GNP-incorporated epoxy composites. The effect of the silanization is evaluated using transmission electron microscopy (TEM), scanning electron microscopy, thermogravimetric analysis, and energy dispersive X-ray spectroscopy. The electrical and thermal conductivities are characterized. The epoxy/silanized GNPs exhibits higher thermal and electrical properties than the epoxy/raw GNPs due to the improved dispersion state of the GNPs in the epoxy matrix. The TEM microphotographs and Turbiscan data demonstrate that the silane molecules grafted onto the GNP surface improve the GNP dispersion in the epoxy.