• Macromolecular Research
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• v.13 no.3
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• pp.194-205
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• 2005

The network structure of Ni-coated carbon black (NCB) composites filled with phenolic resin was investigated by means of using scanning electron microscopy, viscosity, interfacial tension, shrinkability, Flory-Huggins interaction parameters, and swelling index. The electrical properties of the composites have been characterized by measurement of the specific conductivity as a function of temperature. Additionally, the variation of conductivity with temperature for the composites has been reported and analyzed in terms of the dilution volume fraction, relative volume expansion, and barrier heights energy. The thermal stability of phenolic-NCB composites has been also studied by means of the voltage cycle processes. The experimental data of EMI wave shielding were analyzed and compared with theoretical calculations. The mechanical properties such as tensile strength, tensile modulus, hardness and elongation at break (EB) of NCB-phenolic resin composites were also investigated.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.10 no.1
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• pp.24-41
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• 1984

Tallow fatty acid consists of mixtures of fatty acids differing in chain length and saturation. In separation of tallow fatty acid, the effects of the type and concentration of detergents and electrolytes were studied. And the changes of acid composition of particular fractions were determined by gas-chromatography. Sodium lauryl sulfate (SLS), sodium lauryl ether sulfate (SLES) and sodium lauryl benzene sulfonate (SLBS) were used as detergents and NaCl, Na2SO4 and MgSO4 were used as electrolytes. At low concentration of detergent, the tallow fatty acid was not fully wetted, and at high concentration, the emulsion was so stable that the tallow fatty acid was not well separated. The addition of proper amount of electrolyte increased the separation efficiency by the decrease of interfacial tension and by the increase of the amount of adsorbed detergent on the surface of solid fatty acid crystals. The optimum range of detergent was 0.4-0.6% (wt.) in SLS, 0.2-0.4% in SLES and 2.0-) .0% in SLBS. And the optimum range of electrolyte was 2.0-2.5% in NaCl, 3.0-4.0% In Na2SO4 and 0.5-1.0% in MgSO4 respectively.

• Journal of Welding and Joining
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• v.16 no.4
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• pp.109-116
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• 1998

The three-dimensional profile of a solder fillet is predicted by minimizing the surface tension and gravity energies of the solder joint using finite element modeling. Geometric complexity stemming from the inclined plane of the gullwing lead is resolved by employing three element types. These element types are used to describe the joint profile formed on the vertical, inclined and interfacial planes. The predicted solder joint profiles show good agreements with the experimental data provided that the solder volume is adjusted considering the wicking effects. Effects of the pad length, inclined lead angle and solder volume on joint profiles are also investigated.

• Korean Membrane Journal
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• v.1 no.1
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• pp.43-49
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• 1999

Separation of soluble oil was investigated during filtration of cutting oil emulsion using various commercial ultrafiltration membranes. The surface properties of membranes used were hydrophilic hydrophobic and modified surfaces by various surfactant pretreatments. Conditions varied include stirring speed transmeembrane pressure membrane type and surfactant type for pretreatment. The results give some indication of mechanisms occurring at the membrane surface. Surfactant pretreatments significantly improved water flux and UF flux of hydrophilic regenerated cellulose(up to 2.4x for YM100) and hydrophobic polysulfone (up to 2.2x for PTHK) membranes depending on surfactant type and operating conditions. The UF flux enhancement was attributed to membrane swelling and reduction of interfacial surface tension between oil droplets and membrane surface. unexpectedly the hydrophilic membranes revealed greater flux enhancement than the hydrophobic membranes. The results also showed a greater improvement in UF flux at lower operating pressure.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.914-916
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• 2009

Using gelatin and acacia as wall and electronic ink as core substance, microcapsules were prepared by complex coacervation to fabricate a flexible electronic paper display. In order to obtain the microcapsules in a narrow dispersed distribution, we focus on the interfacial tension between the hydrophobic electrophoretic ink and an aqueous polyelectrolyte solution, through controlling sodium dodecyl sulphate (SDS) concentration and stirring rate. The existence of anionic surfactant of SDS not only decreases the droplet diameters, but also reduces the diameter size distribution. And, as the stirring rate is increased, the average size of microcapsule is also decreased.

• Journal of computational fluids engineering
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• v.12 no.4
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• pp.14-19
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• 2007

We present a direct numerical simulation technique and some preliminary results of the capillary spreading of a droplet containing particles on the solid substrate. We used the level-set method with the continuous surface stress for description of droplet spreading with interfacial tension and employed the discontinuous Galerkin method for the stabilization of the interface advection equation. The distributed Lagrangian-multipliers method has been combined for the implicit treatment of rigid particles. We investigated the droplet spreading by the capillary force and discussed effects of the presence of particles on the spreading behavior. It has been observed that a particulate drop spreads less than the pure liquid drop. The amount of spread of a particulate drop has been found smaller than that of the liquid with effectively the same viscosity as the particulate drop.

• Proceedings of the SCSK Conference
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• 2003.09b
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• pp.379-391
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• 2003

Nanoemulsions have many specific characters compared with general emulsions in aspect of stability, rheological property, uniformity, high interfacial tension and so on. Therefore we study on nanoemulsions with changing various lecithins and oils using microfluidizer. As lecithins, we used saturated lecithin, unsaturated lecithin and hydrogenated phosphatidylcholine. Caprylic capric triglyceride, Squalane, Macadamia nut oil, Liquid paraffins, Dimethicone, and Cyclomethicone were used as oils. To identify nanoemulsions, we measured paticle size, zeta potential, turbidity and transmission electron microscope.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.669-672
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• 2006

Recently, large efforts have been made to develop and understand the behavior of Fiber Reinforced Concrete. As in the static loading cases, many researches have been done. However, a few studies have been conducted in cyclic behaviors of FRC. The main objective of the present work is to investigate the cyclic behavior of fiber reinforced concrete with theoretical method. First, cyclic constitutive relations which describe the crack bridging stress considering non-uniform interfacial bond degradation in short randomly oriented fiber reinforced matrix composites under uniaxial cyclic tension were considered. A cyclic degradation model of single fiber based on micromechanics also taken into consideration. As an example, fatigue analysis for ECC with PVA fiber was conducted using proposed equations. Results shows that proposed method can establish a basis for analyzing cyclic behavior of fiber reinforced composites.

• The Korean Journal of Rheology
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• v.10 no.1
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• pp.14-23
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• 1998

비상용성 고분자 브렌드계인 PS/PP와 EPDM/PP의 유변학적 거동에 미치는 계면의 영향을 알아보았고 그실험 결과를 Park & Lee 모델과 비교하였다. PS/PP와 EPDM/PP 블 렌드계에서의 계면에 의한 전단응력과 법선 응력차에의 기여도는 $textsc{k}$와λ(1-$\mu$), 두 개의 변 수에 의해 잘설명되었다. 특히 계면의 탄성적인 효과와 관련있는 법선응력차 항이 전단 응 력 항보다 더 뚜렷하게 나타났다. 30PS/70PP 블렌드 조성에서는 블렌드의 유변학적 특성이 주로 연속상을 이루는 고분자의 의해 좌우된 반면에 50PS/50PP 블렌드조성에서는 계면에 의한 영향이 더두드러지게 나타났다. 이것은 50/50 블렌드 조성에서 계면의 넓이가 증가한 것과 관계 있다. 그러나 EPDM/PP 블렌드계에서 계면에 의한 응력 항들이 모두 PS/PP 블 렌드계의 그것보다 매우 큰 값을 가졌지만, 그 상대적인 비를 나타내는 $textsc{k}$값은 작았다. 이것 은 블렌드를 구성하고 있는 순수한 성분의 법선응력차 값의 차이가 크기 때문이다. 또한 PS/PP 블렌드계에 대한 동적 계면장력을 Park & Lee 모델을 이용하여 예측해 보았다.

• Macromolecular Research
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• v.17 no.3
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• pp.163-167
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• 2009

This study presents a microfluidic method for the production of monodisperse poly(ethylene glycol) (PEG) microspheres using continuous droplet formation and in situ photopolymerization in microfluidic devices. We investigated the flow patterns for the stable formation of droplets using capillary number and the flow rate of the hexade-cane phase. Under the stable region, the resulting microspheres showed narrow size distribution having a coefficient of variation (CV) of below 1.8%. The size of microspheres ($45{\sim}95{\mu}m$) could be easily controlled by changing the interfacial tension between the two immiscible phases and the flow rates of the dispersed or continuous phase.