• Polymer(Korea)
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• v.31 no.6
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• pp.474-478
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• 2007

Polymer substrate materials with low dielectric loss were obtained by fabricating the composite using dicyclopentadienyl bisphenol cyanate ester oligomer and polyphenylene ether (PPE). From the analysis of the curing reaction of oligomer and catalyst, it was observed that the optimum amount of catalyst was 0.02 phr of Zn content. It was applied to the fabrication of polymer composite. By changing oligomer/PPE weight ratio, the peel strength and the gel content of the fabricated composites were measured, and then, the dielectric constant and the dissipation factor were measured in the GHz frequency range. The amount of PPE affected the peel strength and the dielectric properties of composites. However, the amount of catalyst did not affect them at all. Resulting from all experiments, we obtained polymer composite laminates haying the peel strength of above 1 kN/m and the low dissipation factor of 0.004 at 1 GHz.

• Journal of the Korean Chemical Society
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• v.30 no.3
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• pp.320-326
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• 1986

The antitumor properities of metal are not limited to Pt(II) complexes. Recently, it was reported that some Pt(II) and Pd(II) complexes with sulfur and nitrogen ligands had potential antitumor reactivity. Pt(II) complexes is toxic drug for anticancer. Therefore, the complexes of Pd(II) with adenine, uracil, cytosine and malonate ligands are interesting for anticancer drug. We synthesized new palladium complexes containing nucleosides. The reactions of Pd(II) with adenine, uracil, cytosine and malonate ligands have been studied in aqueous solutions. The complexes isolated from these reactions have the following formulas; $[Pd(en)(C_5H_5N_5)_2](NO_3)_2,\;[Pd(en)(C_4H_3N_2O_2)Cl],\;[Pd(en)(C_3H_2O_4)]\;and\;[Pd(en)(C_4H_5N_3O)_2](NO_3)_2{\cdot}(C_4H_5N_3O)$. The compounds have been identified by elemental analysis, mass spectra, infrared spectra and electronic spectra.

• Journal of Korean Association for Spatial Structures
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• v.9 no.2
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• pp.83-90
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• 2009

The previous studies for dynamic behavior of spatial structure have been zoomed in on roof structure by numerical analytic method. But the roof structure of real spatial structures is supported by lower structure as column and wall. So, when earthquake is occurred, it is predicted that dynamic behavior of roof structure is affected by lower structure. Therefore, on this study, natural period characteristics of arch structures are analyzed according to section, length and the modulus of elasticity of brass column and polycarbonate column and additional mass of roof structure by the scale-down model of arch structure as the most simple structure of spatial structures. The changes of natural periods are generally alike. But, when Polycarbonate column is connected to roof structure, the change of natural period for change of section is relatively large. That means that change of section and section and length of column and additional mass of roof structure have less influence on change of stiffness because the modulus of elasticity of brass is relatively large.

• Elastomers and Composites
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• v.48 no.4
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• pp.300-305
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• 2013

Part shrinkage in injection molding is inevitable phenomenon. Thus, it is necessary not only study on the reducing part shrinkage but characterization of part shrinkage. In this study, part shrinkage in injection molded 2.5 dimensional annular shaped specimens has been studied using glass fiber reinforced PC. Annular shaped specimens were designed with various sizes of outer diameter and thickness. Injection temperature, packing time and packing pressure were selected for operational conditions. Profile variations of outer and inner diameters of molded specimens for various operational conditions were investigated. Sizes of outer and inner diameters of injection molded specimens were smaller than the sizes of mold. Part shrinkage decreased as outer diameter and thickness increased. Part shrinkage showed anisotropic behavior and it depended upon gate location. Subsequently, molded specimens were not circular but oval in shape, and showed the largest shrinkage in the direction of gate. It was realized that the mold design such as gate design is important to control the shape of molded products.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1345-1354
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• 2014

This paper has analyzed how the format of the text page and the contents of space surrounding the text in the news stories of the portal sites are made-up. The result of analysis showed that the formats of the text page in Naver news story were more intricate than those of Daum, Nate and Yahoo. Also, Naver was higher in the number of advertising, the type of advertising, the entertainment contents, and various types of contents than other three portals. Especially, the percentage of new story related to entertainers was the highest. It was the portal site Daum that advertised the news story most of all in its text page. In contrast, it was portal site Yahoo that inserted the advertisements least of all. But from the whole sides, it was found that the formats and contents of the text page of the news story in these three portal sites have similarly been made-up. Consequently speaking, for the serviceability of use in news story, it can be evaluated that the news service method in portal sites is higher than that in press dot coms.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.13-19
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• 2018

Effects of multiwall carbon nanotube (MWCNT) type and flow type (shear and elongational flow) on the electrical conductivity of polycarbonate (PC)/ MWCNT nanocomposites were investigated. Two different MWCNTs produced a huge difference in electrical conductivity in an injection molded PC/MWCNT nanocomposite. It was observed that MWCNTs having a higher aspect ratio provide much lower electrical conductivity in injection molded PC/MWCNT nanocomposites while the conductivities of compression molded samples from two different MWCNTs were the same. We found that this is due to a difference in the deformability of the two MWCNTs. As the aspect ratio of the MWCNT increases, the orientation of MWCNT by the external force becomes easier and the conductive path diminishes. Consequently the conductivity of the nanocomposites decreases. Nanocomposite samples prepared at a higher extensional rate and shear rate showed lower electrical conductivity. This is also attributed to the flow induced orientation and reduced conductive path of the MWCNTs. The experimental results were discussed in relation to variation in the tube-tube contact due to the change of the MWCNT orientation.

• Polymer(Korea)
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• v.37 no.2
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• pp.167-176
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• 2013

Linear and cross-linked waterborne polyurethanes (WPUs) based on isophorone diisocyanate and mixed diols of poly(tetramethylene glycol)/hydroxyethyl-terminated polydimethylsiloxane (PDMS-OH) were synthesized with dimethylol propionic acid as an anionic component, trimethylolpropane as a cross-linking agent, and butanediol as a chain extender and characterized. The hydrophobicity, $T_g$, stress-strain behaviors of the linear or cross-linked siloxane-containing WPU (WPU-Si) films with different PDMS content were analyzed by using water contact shape analyzer, energy dispersive spectrometer, dynamic mechanical analyzer, and universal testing machine. The results reveal that as the PDMS content increased, the hydrophobicity of WPU-Si films increased, $T_g$ moved to higher temperature, the breaking stress increased, and the breaking strain decreased.

• Polymer(Korea)
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• v.39 no.2
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• pp.235-239
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• 2015

In this work, we evaluated catalytic activity of LiOH, $Cu(acac)_2$ and n-butyltin hydroxide oxide hydrate in the early stage of the melt transesterification of isosorbide and bisphenol A as diol monomers and diphenylcarbonate for the melt polymerizaiton of polycarbonate. $Cu(acac)_2$ proved to be the most active catalyst for homopolymerization process, while the catalytic activity of LiOH was higher than the others in case of melt copolymerization depending on the catalytic mechanism and chemical structure of catalyst. We suggested that evaluation of catalytic activity can be used for selection of catalyst system in bio-based copolymerization of polycarbonate.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.732-738
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• 2011

Effect of metal oxide catalysts and ionic liquids on the synthesis of methyl carbamate(MC) and dimethyl carbonate (DMC) from urea and methanol was investigated in a high pressure reaction system. In closed system, MC yield from urea and methanol reached almost 100% at reaction temperature over $150^{\circ}C$ without catalyst, whereas DMC yield of 1.5% under was obtained irrespective of catalysts used. In DMC synthesis from MC and methanol, $ZnCl_{2}$ showed the highest catalytic activity and led to the DMC yield of 16.3% under optimal conditions. Furthermore, DMC yield can be enhanced by the simultaneous application of ionic liquids with nano-sized catalysts in semi-continuous reaction system.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.875-879
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• 2008

A method for the depolymerization of polycarbonate waste by glycolysis using ethylene glycol without catalyst was explored in order to get the monomer bisphenol A (BPA). The effect of operation variables such as reaction time, reaction temperature, EG/PC weight ratio and the kinetic of glycolysis were studied. It was found that the polymerization reaction has two different activation energies depending on the reaction temperature. A drop in activation energy with temperature indicates that the reaction mechanism has shifted from one of a succession of elementary steps to another in the series. The maximum yield of BPA of 95.6% was achieved at reaction temperature $220^{\circ}C$ for 85min with EG/PC weight ratio 4.