• Membrane Journal
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• v.21 no.2
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• pp.193-200
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• 2011

An amphiphilic graft copolymer comprising a poly(vinyl chloride) (PVC) backbone and poly (styrene sulfonic acid) (PSSA) side chains (PVC-g-PSSA) was synthesized via atom transfer radical polymerization (ATRP). Mesoporous titanium dioxide $(TiO_2)$ films with crystalline anatase phase were synthesized via a sol-gel process by templating PVC-g-PSSA graft copolymer. Titanium isopropoxide (TTIP), a $TiO_2$ precursor was selectively incorporated into the hydrophilic PSSA domains of the graft copolymer and grew to form mesoporous $TiO_2$ films, as confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The performances of dye-sensitized solar cell (DSSC) were systematically investigated by varying spin coating times and the amounts of P25 nanoparticies. The energy conversion efficiency reached up to 2.7% at 100 mW/$cm^2$ upon using quasi-solid-state polymer electrolyte.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.95-101
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• 2017

In this paper, the sizing removal condition for the pretreatment of composite materials is obtained numerically by applying an image processing algorithm and nickel-plated carbon fiber is fabricated by a dry process method to enhance its electromagnetic shielding performance. Sizings that are wrapped in a polymer type material during the manufacturing of carbon fiber should be removed for dry coating. A numerical value, that is the correlation, can be obtained by determining the regular pattern of the carbon fiber in the image taken by a scanning electron microscope (SEM) after the sizing is removed. The application of the proposed numerical method to the SEM image of the fiber after the sizing is removed with solution, compressed air, solution and compressed air (hybrid), showed that this method of eliminating the sizing is superior to the hybrid method. Then, by spreading the carbon fiber roll with the sizing removed, we were able to produce nickel plated carbon fiber by the roll-to-roll sputtering method. The electromagnetic shielding performance of the fabricated 30, 40 and 100 nickel coated carbon fibers was measured. The Korea Advanced Institute of Science and Technology evaluated the electromagnetic shielding performance of the 100 nickel-coated carbon fiber to have a maximum value of 73.2 (dB) and a minimum value of 66.7 (dB). This is similar to the electromagnetic shielding rate of copper and shows that this material can be used as a cable for EV / HEV automobiles.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.475-480
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• 2017

In this paper, the conductivity of the fine pattern is improved in the insulating substrate by laser-induced forward transfer (LIFT) process. The high laser beam energy generated in conventional laser induced deposition processes induces problems such as low deposition density and oxidation of micro-patterns. These problems were improved by using a polymer coating layer for improved deposition accuracy and conductivity. Chromium and copper were used to deposit micro-patterns on silicon wafers. A multi-pulse laser beam was irradiated on a metal thin film to form a seed layer on an insulating substrate(SiO2) and electroless plating was applied on the seed layer to form a micro-pattern and structure. Irradiating the laser beam with multiple scanning method revealed that the energy of the laser beam improved the deposition density and the surface quality of the deposition layer and that the electric conductivity can be used as the microelectrode pattern. Measuring the resistivity after depositing the microelectrode by using the laser direct drawing method and electroless plating indicated that the resistivity of the microelectrode pattern was $6.4{\Omega}$, the resistance after plating was $2.6{\Omega}$, and the surface texture of the microelectrode pattern was uniformly deposited. Because the surface texture was uniform and densely deposited, the electrical conductivity was improved about three fold.

• Membrane Journal
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• v.15 no.2
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• pp.147-156
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• 2005

It is well-known that polyethersulfone (PES) has high $CO_2$ selectivity over $N_2\;(or\;CH_4)$ and excellent pressure resistance of $CO_2$ plasticization among muy commercialized engineering plastics[1-4]. Asymmetric PES hollow fiber membranes for flue gas separation were developed by dry-wet spinning technique. The dope solution consists of PES, NMP and acetone. Water and water/NMP mixtures are used in outer and inner coagulants, respectively. Gas permeation rate (i.e., permeance) and $CO_2/N_2$ selectivity were measured with pure gas, respectively and the micro-structure of hollow fiber membranes was characterized by scanning electron microscopy. The effects of polymer concentration, ratio of NMP to acetone, length of air gap, evaporation condition and silicone coating were investigated on the $CO_2/N_2$ separation properties of the hollow fibers. Optimized PES hollow fiber membranes exhibited high permeance of $25\~50$ GPU and $CO_2/N_2$ selectivity of $30\~40$ at room temperature and have the apparent skin layer thickness of about $0.1\;{\mu}m$. The developed PES hollow fiber membranes, would be a good candidate suitable for the flue gas separation process.

• Membrane Journal
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• v.26 no.1
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• pp.76-85
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• 2016

Fabrication of polysulfone (PSf) hollow fiber membranes was investigated for the separation of $N_2/NF_3$ gas mixtures, which are emitted from the display and the semiconductor industries. A combination of the non-solvent induced phase separation (NIPS) and the vapor-induced phase separation (VIPS) technique was applied to develop high flux hollow fiber membranes. Thin polymer layers were further coated onto the surface of the hollow fiber membranes by using polydimethylsiloxiane (PDMS) or Teflon AF1600(R), which contributes to improve the $N_2/NF_3$ selectivity. The $N_2/NF_3$ separation performances of our PSf hollow fiber membranes were determined by the intrinsic properties of coating materials. Especially, the PSf hollow fiber membrane coated with Teflon AF 1600(R) exhibited a higher $N_2/NF_3$ selectivity (> 14) with a slightly lower $N_2$ permeance (4.5 GPU), as compared to the commercial PSf counterparts. This feature provides a good potential as a membrane structure to separate $N_2/NF_3$.

• Journal of the Korea Concrete Institute
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• v.29 no.2
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• pp.131-139
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• 2017

Recently, earthquakes have frequently occurred near Korean peninsula. An experimental study is needed for developing a reinforcing method for seismic strengthening to apply to RC structures. Recently, PolyUrea (PU) as structural reinforcement materials has been receiving great interest from construction industry. The reinforcing effect of PU appeared to be excellent under blast and impact as well as earthquakes. In this study, Flexible Type PolyUrea (FTPU) developed in preceding studies was modified to develop Stiff Type PolyUrea (STPU) by varying the ratio of the components of prepolymer and hardener of FTPU. The material performance evaluation has been performed through hardening time, tensile strength and percent elongation test, pull-off test, and shore hardness test. The experimental results showed that STPU has higher tensile strength and lower elongation than FTPU. Therefore, STPU coating agent can be used for semi-permanent products. By using STPU with Fiber-Reinforced Polymer (FRP) on concrete columns, confinement effect can be enhanced to maximize seismic strength and ductility.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.118-125
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• 2017

In this study, we examined the bond performance of FRP Hybrid Bars. FRP Hybrid Bars are developed by wrapping glass fibers on the outside of deformed steel rebars to solve the corrosion problem. The surface of the FRP Hybrid Bars was coated with resin and silica sand to enhance its adhesion bonding performance with concrete. Various parameters, such as the resin type, viscosity, and size of the silica sand, were selected in order to find the optimal surface condition of the FRP Hybrid Bars. For the bonding test, FRP Hybrid Bars were embedded in a concrete block with a size of 200 mm3 and the maximum load and slip were measured at the interface between the FRP Hybrid Bar and concrete through the pull-out test. From the experimental results, the maximum load and bond strength were calculated as a function of each experimental variable and the resin type, viscosity and size of the silica sand giving rise to the optimal bond performance were evaluated. The maximum bond strength of the specimen using epoxy resin and No. 5 silica sand was about 35% higher than that of the deformed rebar.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.741-748
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• 2019

As the occurrence of harmful algal blooms (HABs) have become severe in precious water resources, the development of efficient harmful algae treatment methods is considering as an important environmental issue for sustainable conservation of water resources. To treat HABs in water resources, various conventional physical and chemical methods have been utilized and showed treatment efficiency, However, these methods can lead to discharging of cyanotoxins into the water bodies by chemical or physical algal cell lysis or destruction. Thus, to overcome this limitation, the development of safe HABs treatment methods is required. In the present study, adsorption technology was investigated for the removal of harmful algal species, Microcystis aeruginosa from aqueous phases. Industrial waste biomass, Corynebacterium glutamicum biomass was valorized as biosorbent (PEI-modified alginate/biomass composite fiber; PEI-AlgBF) for M. aeruginosa through immobilization with alginate matrix and cationic polymer (polyethylenimine; PEI) coating. The functional groups characteristic of PEI-Alg was determined using FT-IR analysis. By adsorption process used PEI-AlgBF, 52 and 67% of M. aeruginosa could be removed under the initial density of M. aeruginosa 200×10⁴ cells mL^-1 and 50×10⁴ cells mL^-1, respectively. As the increasing surface area of PEI-AlgBF, the removal efficiency was increased. In addition, we could find that adsorptive removal of M. aeruginosa has occurred without any M. aeruginosa cell lysis and destruction.

• Journal of the Korean Chemical Society
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• v.47 no.6
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• pp.601-607
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• 2003

We studied on preparation of nanoparticles modified surface using biodegradable polymer, poly(DL-lactide-co-glycolide) (PLGA). Two kinds of PLGA nanoparticles were prepared by a spontaneous emulsification solvent diffusion (SESD) method using cetyltrimethylammonium chloride (CTAC) and tetradecyltrimethylammonium bromide (TTAB) as a cationic surfactant and polyethylene glycol-block-polypropylene glycol copolymer (Lutrol F68) as a nonionic surfactant. Model protein was coated on the surface of nanoparticles by the ionic complexation. The model protein was that influenza vaccine ($H_3N_2,\;H_1N_1$, B strain) labeled with NHS-fluorescein. The sizes of cationic nanoparticles were 140-160 nm and the surface charges were 50-60 mV. The sizes of nonionic nanoprticles were 80-90 nm and the surface charge was -10 mV. After coating vaccine on the surface of nanoparticles, the sizes of cationic nanoparticles were increased to 380-400 nm and the size of nonionic nanoparticles was not increased. The amount of coated vaccine on the cationic nanoparticles was 22.73 ${\mu}g$/mg.

• Clean Technology
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• v.18 no.2
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• pp.170-176
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• 2012

A series of acrylic copolymers containing perfluoroalkyl acrylate were synthesized by 2-step emulsion polymerization of variety of acrylate monomers (ethyl acrylate, butyl acrylate or methyl methacrylate) with perfluoroalkyl ethyl acrylate (PFA) and glycidyl methacrylate (GMA) monomers. This study focused on effects of monomer compositions (the kind of acrylate monomer, contents of PFA and GMA) and composition of surfactants [(sodium dodecyl sulphate/nonylphenol 10mole ethoxylate (NP-10)] and initiator content on the contact angles and surface free energy. It was found that the copolymer having an optimum composition (BA : 87 wt%, GMA : 8.7 wt% and PFA : 4.3 wt%) was shown to be quite surface active [surface free energy : 19.89 mN/m and contact angles : $103.5^{\circ}$ (water) and $78.7^{\circ}$ (methylene iodide)] in the solid state. This result suggests that the optimal copolymer containing fluorinated monomer synthesized in this study have high potential as a low surface energy material, which may have high oil- and water-repellent surface and have been proposed as acrylic syntan for leather and also as soil-resistant/oil and water repellent coating for textiles and wood etc.