• Corrosion Science and Technology
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• v.6 no.2
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• pp.68-73
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• 2007

The toxicity of chromium that is used to impart corrosion resistance to galvanized steel created environmental and health-related concerns and generated a great deal of interest in developing chrome-free treatment coatings. In the present work, organic-inorganic composite coatings were used to coat electrogalvanized steel (EG) sheets for corrosion protection without degrading its weldability property. The new coatings composed of specially modified polyurethane dispersion hybridized with silicate and unique inorganic-organic inhibitors were developed during this work. It was found that about $1{\mu}m$ thickness of coating layer is secure enough in corrosion resistance of flat and formed part even after alkaline degreasing. Overall chemical resistances including fingerprint resistance and paint adhesion property were satisfied with the test specification of Sony technical standard of SS-00260-2002. Therefore, it is concluded that the newly developed chrome-free product can replace the conventional chromated product.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.125-128
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• 2005

The dispersion of carbon nanofiber (CNF) was carried out by solution blending, mechanical mixing, and sonication. CNFs at levels of 5-50% fiber weight content were mixed with polypropylene (PP) powder, and then were melt-mixed using a twin-screw extruder. For the further alignment of fibers, extruded rods were stacked uni-directionally in the mold cavity for the compression molding. For the evaluation of mechanical properties of nanocomposites, tension, in-plane shear, and flexural tests were conducted. CNF/PP composites clearly showed reinforcing effect in the longitudinal direction. The tensile modulus and strength have improved by 100% and 40%, respectively for 50 % fiber weight content, and the flexural modulus and strength have increased by 120% and 25%, respectively for the same fiber weight content. The shear modulus showed 65% increase, but the strength dropped sharply by 40%. However, the property enhancement was not significant due to the poor adhesion between fiber and matrix. In the transverse direction, the tensile, flexural, and shear strength decreased as more fibers were added.

• Journal of the Korea Institute of Building Construction
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• v.4 no.3
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• pp.93-100
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• 2004

In recent years, it has widely been studied on the light-weight composites for the purpose of the large space and thermal insulation of building structures. The purpose of this study is to evaluate the properties of light-weight composites made by binders as cement, resin and polymer cement slurry. The concrete composites are prepared with various conditions such as polymer-cement ratio, void-filling ratio, type of resin, filler content and light-weight aggregate content, tested for thermal conductivity. From the test results, the thermal conductivity of concrete composites with the binder of cement tends to decrease with increasing polymer-cement ratio, and to increase with increasing void-filling ratio. The thermal conductivity of concrete composites with the binder of resin are markedly affected by the light-weight aggregate content, type of resin and filler content. The composites made by polymer-modified concrete and polymer cement slurry have a good thermal insulation property. From the this study, we can recommend the proper mix proportions for thermal insulation Panel or concrete. Expecially. the thermal conductivity of concrete composites made by polyurethane resin is almost the same as that of the conventional expanded polystyrene resin.

• Journal of the Korean Applied Science and Technology
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• v.26 no.3
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• pp.288-296
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• 2009

In this study, the silica-based hybrid material with high barrier property was prepared by incorporating ethylene-vinyl alcohol (EVOH) copolymer, which has been utilized as packaging materials due to its superior gas permeation resistance, during sol-gel process. In preparation of this EVOH/$SiO_2$ hybrid coating materials, the (3-glycidoxy-propyl)-trimethoxysilane (GPTMS) as a silane coupling agent was employed to promote interfacial adhesion between organic and inorganic phases. As confirmed from FT-IR analysis, the physical interaction between two phases was improved due to the increased hydrogen bonding, resulting in homogeneous microstructure with dispersion of nano-sized silica particles. However, depending on the range of content of added silane coupling agent (GPTMS), micro-phase separated microstructure in the hybrid could be observed due to insufficient interfacial attraction or possibility of polymerization reaction of epoxide ring in GPTMS. The oxygen barrier property of the mono-layer coated BOPP (biaxially oriented polypropylene) film was examined for the hybrids containing various GPTMS contents. Consequently, it is revealed that GPTMS should be used in an optimum level of content to produce the high barrier EVOH/$SiO_2$ hybrid material with an improved optical transparency and homogeneous phase morphology.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.5
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• pp.657-664
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• 2013

By using shear mixing and ultrasonication, we fabricated specimens of well-dispersed multi-walled carbon nanotube composites. To confirm the proper dispersion of the filler, we used scanning electron microscopy images for quantitative evaluation and a tensile test for qualitative assessment. Furthermore, the coefficients of thermal expansion of several specimens having different filler contents were calculated from the measured thermal strains and temperatures of the specimens. Based on the microscopy images of the well-dispersed fillers and the small deviations in the measurements of the tensile strength and stiffness, we confirmed the proper dispersion of nanotubes in the epoxy. As the filler contents were increased, the values of tensile strength increased from 58.33 to 68.81 MPa, and those of stiffness increased from 2.93 to 3.27 GPa. At the same time, the coefficients of thermal expansion decreased. This implies better thermal stability of the specimen.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.25-30
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• 2006

When wet soil overlies dry soil, which can be found in the infiltration test, the radar wave is not attenuated and guided within wet soil layer. This phenomenon is known to be the dispersive guided wave and happens when the thickness of upper wet layer is less than or comparable to the wavelength of radar wave. In this study, we have conducted the FDTD modeling and obtained the velocity dispersion curve to identify the dispersive guided wave through F-K analysis. This guided wave can be explained by modal propagation theory and a simple inversion code was developed to obtain the two layer's dielectric constants as well as layer thickness. By inverting the dispersion curve from synthetic modeling data, we could obtain the accurate dielectric constants and layer thickness. Moreover, we could enhance the accuracy by including the higher mode data. We expect this method will be very useful to get the quantitative property of subsurface when the condition is similar.

• Polymer(Korea)
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• v.35 no.1
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• pp.47-51
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• 2011

In this study, illite, an environmental friendly, low cost, and high aspect ratio additive, was used to improve flame retardant property of epoxy and it was fluorinated to enhance dispersion of hydrophilic illite in hydrophobic epoxy by introducing hydrophobic functional groups. Fluorination of illite enhanced illite dispersion ill epoxy solution before curing and that in the complex after curing. These enhanced dispersions were attributed to the increased affinity of illite to hydrophobic epoxy solution induced by fluorination of illite and the increased intercalation of epoxy polymer or exfoliation of illite by epoxy curing. Hence, limited oxygen index(LOI) of fluorinated illite/epoxy complex increased by 24%, compared to that of epoxy, suggesting that the preparation of fluorinated illite/epoxy complex increased their flame retardant properties.

• Polymer(Korea)
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• v.26 no.6
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• pp.803-811
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• 2002

In this study the wear behavior of ultra high molecular polyethylene (UHMWPE) filled with kaolin particles by different methods was investigated. UHMWPE/kaolin composites were prepared by two different methods: polymerization-filling and powder mixing. Particularly in a powder mixing method. Particle dispersion and wear property according to powder mining method were examined. It was found from wear test that filling of inorganic filler into UHMWPE by polymerization filling was more effective way than by powder mixing method in improving Wear resistance of UHMWPE. It was also confirmed that abrasive wear was dominant wear mechanism and particle dispersion in the composite as well as interface property was an important factor in controlling the wear behavior of the resulting composites.

• Clean Technology
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• v.14 no.3
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• pp.193-203
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• 2008

A surfactant is used to assist the effect of cleaning, dispersibility and adhesion during leather manufacturing process. Existing surfactant for that process includes many hydrophilic groups that may cause problem such as stain, bad water resistance and poor durability, etc. It is potential problem to make high-performance property for future leather market. In this study, we have synthesized the fluorinated surfactant of which property decreases surface tension, increases dispersion, cleaning effect and the better chrome absorption by the high bond energy of C-F to complement weakness that the present alkyl derivative surfactants have. Using fluorinated surfactant, we can confirm that dispersion is increased, chrome absorption ratio is augmented with high osmosis and coherence, chrome content in the tanning waste water is reduced, BOD and COD contents are diminished and physical characteristics are improved.

• Food Engineering Progress
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• v.14 no.2
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• pp.118-126
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• 2010

The fibrous material fraction as a by-product from the commercial aloe vera gel processing was obtained and freeze dried. The physicochemical characteristics such as the proximate composition, crystalline/surface structures and several physical functionalities including the water holding capacity (WHC), swelling capacity (SW), oil holding capacity (OHC), emulsion/foam properties and viscosity properties of this powdered sample (100 mesh) were investigated and analyzed by comparison with commercial $\alpha$-cellulose as a reference sample. The total dietary fiber content of powdered sample was very high as much as 87.5%, and the insoluble dietary and soluble dietary fiber content ratios were 77.6 and 22.4%, respectively. The FT-IR spectrum of powdered sample showed a typical polysaccharide property and exhibited a x-ray diffraction pattern for cellulose III and IV like structure. SW (8.24${\pm}$0.15 mL/g), WHC(6.40${\pm}$0.19 g water/g solid) and OHC(10.32${\pm}$0.29 g oil/g solid) of freeze dried aloe cellulose were about 3.3, 1.4 and 2 times higher than those of commercial $\alpha$-cellulose, respectively. Aloe cellulose (~2%, w/v) alone had no foam capacity while improved the foam stability of protein solution (1% albumin+0.5% $CaCl_{2}$) by factor of 300%. Emulsion capacity of 2%(w/v) aloe cellulose was about 70% level of 0.5%(w/v) xanthan gum, but its emulsion stability was about 1.2 times higher than that of xanthan gum. Also, aloe cellulose containing CMC (carboxyl methyl cellulose) of 0.3%(w/v) showed a very good dispersity. Aloe cellulose dispersion of above 1%(w/v) exhibited higher pseudoplasticity and concentration dependence than those of $\alpha$-cellulose dispersion, indicating the viscosity properties for new potential usage such as an excellent thickening agent.