• Composites Research
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• v.26 no.3
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• pp.170-174
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• 2013

Atmospheric glow plasma polymerization was applied to wood powder before fabricating polypropylene (PP) matrix composites. Seven different types of monomers (Oxygen, Benzene, CH4, Acrylic-acid, Hexafluoroethane, Trifluorotolune, Hexamethyl-disiloxane) were analyzed to determine the most suitable precursor for plasma polymerization. The surface energy was calculated from measured contact angle about each monomer on PP. Hexamethyl-disiloxane (HMDSO) had a highest surface energy and is selected as the most suitable monomer. Wood powder and polypropylene were mixed as pellets by twin screw extruder and then 50 wt% wood powder/PP composites were produced by an injection machine. Tensile strength and Flexural strength have improved by 7.59% and 12.43% at the maximum respectively. SEM (Scanning Electron Microscope) observation on the fracture surface revealed that the plasma polymerization have improved the interfacial bonding and the mechanical properties of the composites.

• Journal of Adhesion and Interface
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• v.9 no.1
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• pp.9-15
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• 2008

EVA foam was treated by oxygen plasma under a various treatment time for surface modification. The effect of plasma treatment on surface properties of EVA foam was investigated in terms of FT-IR ATR, XPS, contact angle, and SEM analysis and the adhesion characteristic of the EVA foam was studied in peel strength. As a results, EVA foam treated by plasma led to an elimination of organic compound, an increase of oxygen content, and an increase of surface roughness, resulting in improving the adhesion properties of the EVA foam. As the plasma treatment time increased, the hydrophilicity and physical change of surface of the EVA foam were increased and showed maximum value at 180 s and 420 s, respectively. The maximum adhesion strength appeared at plasma treatment time of 420 s and therefore, in this study the physical change was thought to be a major factor for improving the adhesion of the EVA foam.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.116.2-116.2
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• 2015

우리는 실리콘 마이크로구조-ZnO 나노막대 피라미드 구조의 제작 및 표면 특성에 대해서 연구했다. 실리콘 마이크로 피라미드 배열을 구성하는 에칭된 기판 위에 임의의 주기적인 계층 구조로 된 ZnO 나노막대를 성장시켰다. 습식 화학 에칭은 피라미드의 Si 미세 구조를 제작하기 위해 사용되며, 산화 아연 나노막대를 $90^{\circ}C$에서 수열 합성 방법으로 성장시켰다. 본 연구에서는 성장 시간과 피라미드 크기에 따라 ZnO 나노막대 길이와 두께를 조절하여 표면적을 넓히는 실험을 진행하였다. 성장시킨 ZnO 나노 구조들은 XRD (X-ray diffraction), FE-SEM (Field Emission Scanning electron microscopy), WCA (Water contact angle)를 통해 특성을 분석하였다. 젖음성 연구를 통해 ZnO 나노구조가 짧고 긴 성장 시간에 따라 친수성과 초친수성임을 확인하였다.

• Resources Recycling
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• v.7 no.5
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• pp.26-32
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• 1998

Recycline of used plastics is rather restricted due to their variety and difficulties in their separation. In this study, a reliable and economical method for the separation of PVC which utilizes an appropriate control of surface chemistry of pariticles was suggested. this method consists of modification of PET surface from hydrophobic to hydrophilic by NaOH solution and subsequent separation by a froth flotation technique. Flotation results were in terms of NaOH concentration, digestion temperature and time, temperature and pH of solution, PVC concentration. They could be separated up to 95~100% by this method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.9
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• pp.2065-2070
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• 2010

The diluted PMMA treated $SiO_2$ films as an passivation materials for semiconductor devices was researched by using the FTIR spectra. The diluted PMMA solution with various ratios changed the surface of $SiO_2$ film as the hydrophilic, hydrophobic or hybrid type properties. The sample 7 with little carbon content showed dramatically the chemical variation by the FTIR spectra analysis. Beacuse the little carbon with electrons decreased the polarity and surface energy on the $SiO_2$ film, and then became a stable bonding structure and decreased the leakage current. The FTIR spectra can define the detail variation due to the chemical reaction on the organic thin film, and help to research the characteristic of the organic materials.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.7
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• pp.283-287
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• 2016

One of the most important factors for determining the thermal performance of an evaporative cooling system is the wettability of the evaporative heat exchanger surface. Evaporation of a widely spread water film on the heat exchanger surface promotes heat transfer between the "dry" air and "wet" air passages. Hydrophilic coating is generally applied on the heat exchanger surfaces to increase the wettability of the heat exchanger surface and the COP of the evaporative cooling system. In this paper, a simple lamellar patterned structure is suggested to maximize the spreading of a water film on the vertically oriented walls. The capillary height of the lamellar structured grooves is analyzed through a theoretical model, and the results are compared with the numerical analysis through a finite element analysis tool, SE-FIT. A good agreement between the theoretical model and the numerical analysis can be observed as long as the channel depth is comparable to or larger than the channel width of the lamellar structure.

• Polymer(Korea)
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• v.35 no.5
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• pp.390-394
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• 2011

Effects of silver nanoparticles on the polymerization rate and morphology of poly(vinyl acetate) (PVAc)/silver microspheres prepared by suspension polymerization of VAc were investigated. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction and atomic absorption spectrometry were used to characterize the morphology and properties of the PVAc/silver microspheres. Due to the change of hydrophilicity of silver nanoparticles, appearance of the microspheres having golf ball-like convave surfaces was observed. Under controlled concentration of surfactant, PVAc/silver microspheres with various hollow structures were synthesized. In the case of silver nanoparticles modified by surfactant, the polymerization rate increased slightly. PVAc/silver microspheres with a conversion up to 80% were prepared via suspension polymerization.

• Polymer(Korea)
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• v.32 no.1
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• pp.7-12
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• 2008

We confirmed that poly (ethylene terephthalate) (PET) fiber had the possibility to improve the mechanical properties of polypropylene (PP) by fabricating PP/PET fiber composites because PET enhanced mechanical properties and higher melting temperature than PP. But lower compatibility of between PP and PET fibers induced poor mechanical properties of PP/PET fiber composites in spite of incorporating PP-g-MAH as compatibilizer. To solve these problems of PP/PET fiber composites, we carried out a surface treatment on PET fiber using NaOH solution and Prepared PP/PET fiber composites with good mechanical properties by adding PP-g-MAH as a compatibilizer Then the behavior of the mechanical properties was correlated with the results obtained from SEM and IR spectroscopy.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2011.11a
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• pp.63-63
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• 2011

통상적으로 코팅가공시 수지의 흐름성을 개선하기 위해서 코팅수지(점도 : 50,000~60,000 Cps)의 점도를 10,000 Cps 이하로 낮추어서 작업을 진행한다. 이때 MEK(Methyl Ethyl Ketone), TOL(Toluene), DMF(Dimethyl Formamide) 등과 같은 유기용제를 사용하여 점도를 조절한다. 본 연구는 기존에 표면처리 코팅용 수지 배합시 유기용제를 사용하는 대신 물을 사용하여 점도 조절이 가능한 표면처리 코팅용 hydrophilic PU 수지를 연구하였다. Prepolymer 법으로 합성한 수지가 One-shot법으로 합성한 수지보다 water dilution 안정성이 우수하며, 친수성 polyol과 소수성 polyol의 비율이 6/4정도가 될 때 water dilution된 수지의 안전성, 투습도 등의 물성이 가장 이상적으로 발현 되는 것을 확인 할수 있었고, 50part의 물과 희석 후 5일 이후에도 상분리가 되지 않음을 확인 할 수 있었다. 개발된 수지의 적용성을 평가한 결과, J-knife를 이용하여 knife over roll 방식으로 $200{\mu}m$의 gap으로 80/120/$140^{\circ}C{\times}10m/min.$의 다단건조 공정으로 진행했을 때 최적의 물성을 얻을 수 있었다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.1
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• pp.95-101
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• 2000

The effect of surface contact angle on the behavior of frost formation in a fin-tube heat exchanger is investigated experimentally. It is shown that both heat exchangers with hydrophilic and hydrophobic surfaces appear to have a better thermal performance than bare aluminium heat exchanger, but the improvements are very small. There is a little increase in the amount of the frost deposited onto the heat exchanger with both hydrophilic and hydrophobic surface. However, the effect of contact angle on the frost density is observed ; the frost with high density forms on the heat exchanger with hydrophilic surface ; and the frost with low density is deposited onto the heat exchanger with hydrophobic surface when compared with the frost deposited onto the heat exchanger with bare aluminium surface. This may be attributed to the fact that the shape of water droplets which condense on the surface of heat exchanger at the early stage of frosting varies with contact angle, and thus makes a difference on the structure of frost formation. From the experiments with different relative humidity of inlet air, it is shown that the variations of operating parameter make no influence on the effect of surface contact angle on the frosting behavior in the heat exchanger.