• Polymer(Korea)
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• v.26 no.4
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• pp.501-507
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• 2002

In this work, diglycidylether of bisphenol-S (DGEBS) epoxy resin was prepared by alkaline condensation of bisphenol-S (BPS) with epichlorohydrin (ECH) in the presence of NaOH catalyst. The structure of the synthesized DGEBS epoxy resin was confirmed by IR, NMR spectra, and elemental analysis. The curing reaction and glass transition temperature ($T_g$) of DGEBS epoxy resin cured with phthalic anhydride (PA) and tetrahydrophthalic anhydride (THPA) at curing agents were studied by dynamic differential scanning calorimetry (DSC). The thermal stability of the cured specimen was investigated by thermogravimetric analysis (TGA). As a result, the activation energy ($E_a$) of DGEBS/PA system was higher than that of DGEBS/THPA system, whereas $T_g$, initial decomposed temperature (IDT), and decomposition activation energy ($E_t$) of DGEBS/PA were lower than those of DGEBS/THPA. This was probably due to the fact that the crosslinking density of DGEBS/THPA was increased by ring strain of curing agent.

• Clean Technology
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• v.17 no.3
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• pp.244-249
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• 2011

We synthesized low molecular-weight polymers bearing hydrophobic and hydrophilic parts in a chain through $CO_2$/propylene oxide copolymerization. When hydrophilic poly (ethylene glycol) bearing -OH group (s) at the end group (s) was added as a chain transfer agent in the $CO_2$/propylene oxide copolymerization catalyzed by a highly active catalyst, block polymers were formed. If poly (ethylene glycol) (PEG) bearing -OH group only at an end was fed, PEG-block-PPC diblock copolymer was obtained. When PEG bearing -OH group at both ends was fed, PPC-block-PEG-block-PPC triblock copolymer was obtained. We confirmed formation of block copolymers by $^1H$-NMR spectroscopy and GPC studies.

• Polymer(Korea)
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• v.38 no.5
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• pp.650-655
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• 2014

The degradation characteristics of perfluoropolyether (PFPE) derivatives currently being used as computer hard disk lubricants have been investigated. Especially, we considered the effects of end group on degradation behavior of PFPE derivatives. It was found that the degradation of PFPE derivatives in the presence of $Al_2O_3$ involves two degradation mechanisms such as thermal degradation and Lewis acid disproportionation by $AlF_3$ which was mainly formed by oxide-to-halide reaction between $Al_2O_3$ and the degraded PFPE. The end groups were strongly related to Lewis acid disproportionation of PFPE derivatives, and it is due to the difference of electron donating ability in the each end groups. Even if PFPE derivatives have same repeating unit in the main chain, Lewis acid disproportionation was prohibited by higher electron donating ability by the end group which caused the high electron density at the acetal group in the repeating unit.

• Journal of Life Science
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• v.18 no.3
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• pp.298-303
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• 2008

Using a phage peptide library approach, we have isolated a peptide ligand that binds to transferrin receptor on the surface of human melanoma cell, B16F10. The library was first screened twice by recovering internalized phages and was further screened three times by competitively eluting transferrin receptor-specific phages with human transferrin among the phages bound to the cell surface. The peptides displayed by the selected phages were fused to translocation and catalytic domain of Pseudomonas exotoxin to prepare recombinant toxins. After estimating cytotoxicity of each recombinant toxin toward B16F10 cell, seven clones were selected. Sequence analysis revealed that one of the clones displayed a peptide which had a significant sequence homology with human transferrin. The peptide was chemically synthesized and was shown to be functional in delivering cytotoxic agents into B16F10 cell via interaction with transferrin receptor.

• Journal of the Korean Chemical Society
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• v.20 no.4
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• pp.299-308
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• 1976

Cerium (Ⅳ) ion-initiated graft copolymerizations of acrylamide and of acrylonitirile to silk fibroins were investigated. When acrylamide was used, the change in ceric ammonium nitrate concentration exhibited a maximum in degree of grafting at 0.01 M. Also observed was that the change in acetic acid content in reaction media gave a maximum in degree of grafting at 7% acetic acid in water. Degree of grafting was increased generally with increase in acrylamide concentration reaction time and reaction temperature. When acrylonitrile monomer was used for grafting,different results were obtained. Addition of nitric acid was more effective in enhancing the degree of grafting than the addition of acetic acid.Generally the grafting of acrylonitrile to silk fibroins was less efficient than the grafting of acrylamide. The portion of grafted silk fibroins insoluble in Lowe's reagent exhibited the IR absorption bands characteristics to both vinyl polymers and silk fibroins, indicating the grafting of vinyl monomers to silk fibroins. To examine the molecular weight of graft vinyl polymer, a sample of grafted silk was hydrolyzed by 10% sodium hydroxide. Viscosity measurements indicated that the molecular weight of the graft polymer was in the range of 105.

• Journal of the Korean Chemical Society
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• v.37 no.10
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• pp.903-909
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• 1993

Reaction mechanism of palladium(0, II)-phosphines complexes catalyzed cyclocarbonylation for unsaturated carboxylic acid such as crotonic acid, methacrylic acid and 3-butenoic acid has been investigated by product analysis, molecular mechanics and extended Huckel molecular orbital method. Reaction of 3-butenoic acid with palladium(0, II)-phosphines catalyst gives palladium containing cycloester through intermediate palladium-olefin ${\pi}$ -complex in the catalytic carbonylation. Palladium(0, II)-phosphines complexes catalyze the cyclocarbonylation of 3-butenoic acid to give 3-methylsuccinic anhydride and glutaric anhydride. But ${\pi}$ -complexes with palladium(0, II)-phosphines and unsaturated carboxylic acids such as crotonic acid and methacrylic acid are not effective the catalytic cyclocarbonylation.

• Magazine of the Korea Concrete Institute
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• v.5 no.4
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• pp.156-166
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• 1993

The results of an experimental study on the manufacture and the mechanical properties of steel fiber reinforced polyester resin composites utilizing industrial waste products(fly ash) are presented in this paper. The composites using steel fiber, fly ash, unsaturated polyester resin, styrene monomer, catalyst (cobalt octate) and accelerator(methyl ethyl ketone peroxide), fine and coarse aggreates were prepared using various mixing conditions. As the test results show. the mechanical and physical properties, such as the compressive, tensile and flexural strengths, and the setting shrinkage of fly ash$\cdot$polyester resin composites were improved considerably by increasing the fly ash-binder ratio. And the workability of steel fiber reinforced fly ash$\cdot$polyester resin composites was reduced with increasing the fly ash-binder ratio and steel fiber content. Also, the compressive, flexural strength and toughness of the composites were remarkably increased by increasing steel fiber content.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.669-675
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• 2008

Carbon black has been widely used in composites, tonor resin, and ink materials. Since carbon black readily agglomerates, it is important to disperse carbon black in real applications. Aiming to improve dispersion stability, carbon black was chemically oxidized to possess hydroxyl groups using a phase transfer catalyst at room temperature. The modified carbon black (CB-OH) was grafted by a silane coupling agent, p-methylacryloxypropyltrimethoxysilane, to carry teminal vinyl groups. The modified carbon black was subsequently used in miniemulsion polymerization to achieve encapsulted core-shell structure. Finally, well-encapsulated carbon black by polymer was obtained in the size range of 100-500 nm. Throughout the polymerization, the effects of surface modification, types of monomers, initiators, and emulsifiers were investigated.

• Clean Technology
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• v.20 no.4
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• pp.359-366
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• 2014

Attrition characteristics of PKM1-SU particles, $CO_2$ absorbents for pre-combustion $CO_2$ capture process, and FCC particles, catalytic particles for hydro cracking of crude oil, were investigated at high temperature and high pressure conditions. Particle attrition tests were executed at various kinds of temperature ($0-400^{\circ}C$) and pressure (0-20 bar) conditions in a cylinder type bubbling fluidized bed with 15.1 cm diameter, 120 cm height and 1 mm orifice-sparger tube. Attrited particles before and after tests were analyzed by BET, optical microscopy, and particle size analyzer. Effects of bed material height (solid inventory) and steam injection were also verified by using ASTM D5757-95, conventional attrition test method.

• Clean Technology
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• v.20 no.1
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• pp.88-94
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• 2014

During the past decades much attention has been paid to the desulfurization of diesel oil which is important as a source for the fuel cells to prevent the sulfur poisoning of both diesel steam reforming catalyst and electrode of fuel cell. Although alternative desulfurization techniques have been investigated, desulfurization for ultra-low sulfur diesel (ULSD) is still challenged. Therefore, this research focuses on the desulfurization of commercial ULSD for the application to molten carbonate fuel cell (MCFC). Herein, the performances of several kinds of commercial adsorbents based on activated carbons, zeolites, and metal oxides for desulfurization of ULSD were screened. The results showed that metal oxides based materials can feasibly reduce sulfur concentration in ULSD to a level of 0.1 ppmw while activated carbons and zeolites did not reach this level at current conditions.