• Journal of Korean Society for Atmospheric Environment
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• v.30 no.4
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• pp.362-377
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• 2014

Polycyclic aromatic hydrocarbons (PAHs) have been of particular concern since they are present both in the vapor and particulate phases in ambient air. In this study, a simple method was applied to determine the vapor phase PAHs, and the performance of the new method was evaluated with a conventional method. The simple method was based on adsorption sampling and thermal desorption with GC/MS analysis, which is generally applied to the determination of volatile organic compounds (VOCs) in the air. A combination of Carbotrap (300 mg) and Carbotrap-C (100 mg) sorbents was used as the adsorbent. Target compounds included two rings PAHs such as naphthalene, acenaphthylene, and acenaphthene. Among them, naphthalene was listed as one of the main HAPs together with a number of VOCs in petroleum refining industries in the USA. For comparison purposes, a method based on adsorption sampling and solvent extraction with GC/MS analysis was adopted, which is in principle same as the NIOSH 5515 method. The performance of the adsorption sampling and thermal desorption method was evaluated with respect to repeatabilities, detection limits, linearities, and storage stabilities for target compounds. The analytical repeatabilities of standard samples are all within 20%. Lower detection limits was estimated to be less than 0.1 ppbv. In the results from comparison studies between two methods for real air samples. Although the correlation coefficients were more than 0.9, a systematic difference between the two groups was revealed by the paired t-test (${\alpha}$=0.05). Concentrations of two-rings PAHs determined by adsorption and thermal desorption method consistently higher than those by solvent extraction method. The difference was caused by not only the poor sampling efficiencies of XAD-2 for target PAHs and but also sample losses during the solvent extraction and concentration procedure. This implies that the levels of lower molecular PAHs tend to be underestimated when determined by a conventional PAH method utilizing XAD-2 (and/or PUF) sampling and solvent extraction method. The adsorption sampling and thermal desorption with GC analysis is very simple, rapid, and reliable for lower-molecular weight PAHs. In addition, the method can be used for the measurement of VOCs in the air simultaneously. Therefore, we recommend that the determination of naphthalene, the most volatile PAH, will be better when it is measured by a VOC method instead of a conventional PAH method from a viewpoint of accuracy.

• Tribology and Lubricants
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• v.34 no.5
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• pp.197-207
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• 2018

Thermal deterioration of fuel due to long-term storage influences engine performance and causes malfunctions. Fuel stability is usually evaluated via heat resistance and thermal stability during a brief heat shock at high temperature; storage stability in this scenario means that there is very little change in the quality of the fuel during long-term storage. In addition, rubber-based products such as oil seals, O-rings, and rubber hoses can influence the quality of the fuel. When these rubber products are in contact with fuel, they can swell, mechanically weaken, and occasionally crack, thus leaking low molar weight rubber and additives including plasticizer and antioxidant into the fuel to degrade its properties and shorten its useful lifetime. This study determines the thermal stabilities of three kinds of synthetic fuels by evaluating their low temperature kinematic viscosities, chemical composition changes via GC analyses, gross heat of combustion, and color changes. We evaluate the compression set of O-rings by immersing one NBR and two FKM rubber O-rings in the three synthetic fuel samples in airtight containers at variable storage temperatures for six months; from this, we estimate the lifetimes of the O-rings using the Power law model. There were very little changes in the chemical compositions and gross heat of combustion after six months of the experiment. The lifetimes are thus dependent on the materials of the rubber products, and in particular, the FKM O-ring was calculated to have a theoretical lifetime of 200 to 5,700 years. These results indicate that the synthetic fuels maintain their physical properties even after long-term storage at high temperatures, and the FKM O-ring is suitable for long-term sealing of these fuels.

• Korean Chemical Engineering Research
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• v.43 no.5
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• pp.632-636
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• 2005

In this work, the effect of chemical treatments on surface properties of SiC was investigated in thermal and mechanical interfacial behaviors of SiC/PMMA nanocomposites. The acid/base value, contact angles, and FT-IR analysis were performed for the study of surface characteristics of the SiC studied. The thermal stabilities of the SiC/PMMA nanocomposites were investigated by thermogravimetric analysis (TGA). Also the mechanical interfacial properties of the composites were studied in critical stress intensity factor ($K_{IC}$) and critical strain energy release rate ($G_{IC}$) measurements. As a result, the acidically treated SiC (A-SiC) had higher acid value than that of untreated SiC (V-SiC) or basically treated SiC (B-SiC). The acidic solution treatment led to an increase in surface free energy of the SiC, mainly due to the increase of its specific component. Thermal and mechanical interfacial properties of the SiC/PMMA nanocomposites, including initial decomposition temperature (IDT), $K_{IC}$, and $G_{IC}$ had been improved in the acidic treatment on SiC. This was due to the improvement in the interfacial bonding strength, resulting from the acid-base interfacial interactions between the fillers and polymeric matrix.

• Journal of the Korean Society of Food Science and Nutrition
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• v.21 no.5
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• pp.551-556
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• 1992

To develop natural antioxidant from spices and control thermal oxidation of edible soybean oil, the available antioxidative compounds of various spices were extracted with edible soybean oil. The storage stability of the oil mixed with purified sardine oil and soybean oil containing that extracts at $37^{\circ}C$ were investigated. Furthermore the antioxidative activity of petroleum ether soluble fractions(PESF) obtained from rosemary on the thermal oxidation of edible soybean oil during heating at $180^{\circ}C$ were also investigated. By mixing with refined sardine oil and soybean oil extracts of rosemary, sage of herb spices and mace of seed spices, the oxidative stabilities were remarkably increased. The thermal oxidation of edible soybean oil was also supressed by the addition of 1.0%(w/w) of PESF obtained from rosemary. Rosemary extract exhibited higher antioxidative activity on thermal oxidation of edible soybean oil than butylated hydroxytoluene.

• Membrane Journal
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• v.20 no.3
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• pp.259-266
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• 2010

Porous poly(propylene) supported gel polymer electrolytes (GPE) were synthesized by thermal polymerization of DEGDMA [Di(ethylene glycol) dimethacrylate] in electrolyte solutions (1 M solution of $LiPF_6$ in EC/DEC 1 : 1 mixture) at $70^{\circ}C$. AC impedance spectroscopy and cyclic voltammetry were used to evaluate its ionic conductivity and electrochemical stability window of the GPE membranes. Lithium ion battery (LIB) cells were also fabricated with $LiNi_{0.8}Co_{0.2}O_2$/graphite and GPE membranes via thermal polymerization process. Through the thermal polymerization, self sustaining GPE membranes with sufficient ionic conductivities (over $10^{-3}\;S/cm$) and electrochemical stabilities. The LIB cell with 5% monomer showed the best rate-capability and cycleability.

• Applied Chemistry for Engineering
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• v.21 no.4
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• pp.424-429
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• 2010

6-Alkyl-3-chromonealdehyde (2,2-dialkyl)hydrazone derivatives were synthesized by dehydration condensation. They are green-emitting materials for organic light emitting device (OLED) composed of electron acceptor of 6-alkyl-3-chromonealdehydes and electron donor of 2,2-dialkylhydrazones in a conjugated structure. The structural properties of reaction products were analyzed by FT-IR and $^1H$-NMR spectroscopy. The thermal stabilities and reactivities were measured by melting points and yields. The UV-visibles and PL properties were also determined by excitation spectra and emission spectra, respectively.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2999-3003
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• 2012

Various types of room temperature ionic liquids (RTILs) containing 1,1-dicyano-1-acetylmethanide anion ($[C(CN)_2(COCH_3)]^-$, $[DCNAcC]^-$) were prepared and their physical and electrochemical properties were studied. All of these ILs exhibited high thermal stabilities over $200^{\circ}C$ and relatively high ionic conductivities up to 29.4 $mS\;cm^{-1}$ at $80^{\circ}C$. Although the ionic conductivity of IL containing bis(trifluoromethanesulfonyl)-imide ($[Tf_2N]^-$) anion is higher than that of ILs bearing $[DCNAcC]^-$ anion, the specific capacitance of ILs bearing $[DCNAcC]^-$ anion are higher than that of IL containing $[Tf_2N]^-$ anion and showed high temperature dependence. Such favorable electrochemical properties of these ILs are likely to be attributed to the efficient dissociation of cation and anion at higher temperature and enhanced electrosorption of $[DCNAcC]^-$ anion at the electrode.

• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2597-2603
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• 2013

The reactions of hydrated $CdCl_2$, $MnCl_2$, and $NiCl_2$ with 2,2'-bipyidine-3,3',6,6'-tetracarboxylic acid ($H_4bptc$) afforded the mononuclear [$Cd^{II}(H_2bptc)(H_2O)_3]{\cdot}H_2O$ (1), linear $\{[Cd(H_2bptc)(H_2O)]{\cdot}3H_2O\}_n$ (2), 3-D heterobimetallic $[NaCd(Hbptc)(H_2O)]$ (3), layer $[Mn(H_2bptc)(H_2O)]_n$ (4) and a dinuclear compound $[Ni_2(H_2bptc)-(H_2O)_2]{\cdot}6H_2O$ (5). These compounds have been characterized by elemental analysis, IR, and their structures have been determined by X-ray crystallography. The thermal stabilities of 1-3 were measured by thermogravimetric analysis (TGA) and their solid state luminescence properties together with the free ligand $H_4bptc$ were investigated at room temperature.

• Polymer(Korea)
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• v.26 no.3
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• pp.381-388
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• 2002

The properties of polyurethane (PU) nanocomposites with organoclay have been compared in terms of their thermo-mechanical properties, morphology, and gas permeability. Hexadecylamine-montmorillonite ($C_{16}$-MMT) was used as an organoclay to make PU hybrid films. The properties were investigated as a function of organoclay content (1-4 wt%) in the PU matrix. Transmission electron microscopy (TEM) photographs showed that most clay layers were dispersed homogeneously into the matrix polymer in nano-scale, although some particles of clay were agglomerated. We also found that the addition of only a small amount of organoclay was enough to improve the thermal stabilities and mechanical properties of PU hybrid films while gas permeability was reduced. Even at low organoclay content (<5 wt%), the PU nanocomposite showed much better thermo-mechanical properties, and lower gas permeability than pure PU.

• Journal of the Korean Applied Science and Technology
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• v.4 no.2
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• pp.7-13
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• 1987

A preliminary investigation was performed to evaluate the possibility of partially replacing palm oil and beef tallow by rapeseed oil for frying oils of instant Ramyon manufacturing. The AOM stability of rapeseed oil was inferior than of palm oil, but was comparable to that of beef tallow. When rapeseed oil was blended with palm oil or beef tallow, the AOM stability of the blended oil was improved. As far as AOM stability is concerned, best results were obtained with a blending ratio of 3 part of rapeseed oil to 7 part of palm oil and a ratio of 4 part of rapeseed oil to 6 part of beef tallow. These blended rapesee oils was retarded the formation of conjugated dienes and polymers during heating. The antioxidative effects on the stabilities of AOM and thermal in blended rapeseed oils showed that TBHQ was superior to tocopherols and a mixture of BHA and BHT was inferior.