• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.533-540
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• 2018

Graphene has been reported to be an excellent lubricant additive that reduces friction and wear when coated on the surface of various materials or when dispersed in lubricants as an atomic thin material with the low surface energy. In this study, alkyl functionalized graphene oxide (FGO) nanosheets for oil-based lubricant additives were prepared by using three types of alkyl chloride chemicals (butyl chloride, octyl chloride, and tetradecyl chloride). The chemical and structural properties of the synthesized FGOs were analyzed by Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), and transmission electron microscope (TEM). The synthesized FGOs were dispersed at 0.02 wt% in PAO-0W40 oil and its tribological characteristics were investigated using a high frequency friction/wear tester. The friction coefficient and the wear track width of poly alpha olefin (PAO) oil added with FGO-14 were tested by a ball-on-disk method, and the measured results were reduced by ~5.88 and ~3.8%, respectively compared with those of the conventional PAO oil. Thus, it was found that the wear resistance of PAO oil was improved. In this study, we demonstrated the successful functionalization of GO as well as the improvement of dispersion stability and tribological characteristics of FGOs based on various alkyl chain lengths.

• Applied Chemistry for Engineering
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• v.31 no.2
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• pp.230-236
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• 2020

In this study, an adhesive tape with water and impact resistance for mobile devices was developed using a UV-curable urethane acrylate based polymer as a substrate. The substrate fabricated by UV-curable materials shows hydrophobicity and poor wettability, which significantly deteriorates the interface-adhesions between the substrate and acrylic adhesive. In order to improve the interface adhesion, 3-glycidoxy-propyl trimethoxysilane (GPTMS), a silane coupling agent having epoxy functional groups, was selected and incorporated into UV-curable urethane acrylate based polymer resins in various contents. The changes of the chemical composition according to the contents of GPTMS was studied with Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) to know the surface bonding properties. Also mechanical properties of the substrate were characterized by tensile strength, gel fraction and water contact angle measurements. The peel strengths at 180° and 90° were measured to compare the adhesion between the substrate and adhesive according to the silane coupling agent contents. The mechanical strength of the urethane acrylate adhesive tape decreased as the silane coupling agent increased, but the adhesion between the substrate and adhesives increased remarkably at an appropriate content of 0.5~1 wt%.

• 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.

• Journal of Powder Materials
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• v.12 no.4 s.51
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• pp.239-248
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• 2005

1990년도 초반에 개발되어 나노분말의 제조 공정으로 집중적으로 연구되어온 화학기상응축공정은 고강도용 나노분말 소재이외에 기능성 자성재료로의 응용에 주로 이용되어 왔다. 최근에는 이러한 응용이외에 나노분말의 표면을 다양한 이종 소재로 응용하고자하는 나노캡슐(혹은 core/shell)화 제조 공정으로 진보되어 다양한 합금 시스템으로 발전하게 되었다. 특히 최근 Particles 2005, Surface Modification in Particle Technology 학회에서는 나노금속 혹은 세라믹 분말에 PMMA, PE등 polymer의 유기화합물의 코팅하여, DNA나 RNA를 부착하거나 추출해내는 나노캡슐화 공정 연구가 매우 활발하게 진행됨을 보여주고 있으며, 이들 나노 캡슐의 개발은 약물전달계(Drug delivery system), 온열치료용 및 MRI 조영제 등의 바이오재료로의 응용가능성이 크게 기대되어 이에 대한 연구들이 활발하게 진행될 것으로 예상된다.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.6
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• pp.713-723
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• 2014

Biofouling in brackish water reverse osmosis (RO) membranes still needs extensive research to understand cause and mechanism and to obtain methods for reduction of its impact on RO applications. Natural compounds with biofilm formation inhibitory properties are being investigated. Two compounds, vanillin and Epigallocatechin gallate (EGCG), were selected due to their great potential on biofilm formation inhibition. Vanillin shows inhibition on quorum sensing mechanisms of biofilm formation. EGCG has potential to inactivate microbial activity. The two compounds were incorporated in typical polyamide reverse osmosis membranes and evaluated on flux behaviours and biofilm formation potential. The surface properties of membrane coated with vanillin were changed tremendously compared to those with EGCG. As a result, the flux was reduced substantially. The biofilm formation seems hindered with EGCG coated membranes compared to the virgin membranes. More research is needed to optimize coating methods applicable to RO membranes and to enhance biofouling reduction.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.60-60
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• 2012

최근 들어서 소비성향의 고급화 추세와 고기능성 및 쾌적성의 추구는 발수성의 개발로 이어져왔다. Polyester, Nylon 등 다양한 합성섬유소재의 발전으로 발수기능이 상품가치의 중요한 요소로 자리잡고 있다. 더 나아가 표면과 이면이 서로 다른 특성을 가지도록 유도하여 편면기능성을 부여하는 가공을 응용한다면 더욱 더 고부가가치를 기대할 수 있다. 본 연구에서는 불소계로 발수 처리된 Polyester직물 및 Nylon/PU 혼방직물에 저온 플라즈마를 출력 50W, 1, 3, 5, 7 분 처리하여 편발수성을 검토하였다. 불소계 발수제로 코팅처리한 Polyester직물의 경우 5분간 Plasma처리하면 접촉각이 미처리 시료의 $149^{\circ}$에서 처리 후, 앞면 $71.56^{\circ}$, 뒷면 $126.94^{\circ}$,Nylon/PU 혼방직물의 경우에는 $155.3^{\circ}$에서 앞면 $63.24^{\circ}$, 뒷면 $139.26^{\circ}$로 크게 편면 친수화 되었다. 그 결과로 볼 때 플라즈마처리에 의해 편면발수 가공으로 서의 효과를 얻을 수 있었다. SEM 관찰을 통해 Polyester직물 및 Nylon/PU혼방 직물에 플라즈마 처리한 후 처리시간에 따른 펴면의 발수가공 층이 파괴되는 것을 알 수 있었다. 이는 표면에서의 발수효과가 플라즈마처리에 의해 친수화가 진행된 결과와 일치한다.

• Elastomers and Composites
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• v.42 no.2
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• pp.75-85
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• 2007

In this study, the new adhesion system was studied to improve the adhesion strength between polyester cord and rubber matrix. In order to enhance the adhesion strength through polyester cord's surface treatment, the NaOH solution was used. The NaOH solution concentrations of 0.03, 0.05, 0.1, 0.2, 0.5, 1 and 5 wt.% were used in surface modifying the polyester cord. The optimum condition showing the maximum adhesion strength of polyester cord with SBR compound containing bonding agent was at NaOH concentration of 0.05 wt.% with treatment time of 10 minutes. When the NaOH solution concentration was above 1 wt.%, the polyester cord due to the excess surface modification was damaged, and resulted in breakage during the adhesion test. Also, the adhesion strength between polyester and SBR could be improved by coating the polyester cord with triallylcyanurate(TC) adhesive. The drying condition of polyester cord coated with TC attributed to the adhesion strength. The maximum adhesion strength was obtained by using the polyester cord dried at $220^{\circ}C$ rather than dried at room temperature.

• Polymer(Korea)
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• v.31 no.6
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• pp.526-531
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• 2007

This paper reports the first results of a series of planarization film study for the stainless steel (SS) substrates for flexible displays. Diglycidyl ether of bisphenol A (DGEBA) and octa(dimethylsiloxypropylglycidylether) silsesquioxane (OG) were chosen for the organic and the hybrid epoxies respectively and diaminodiphenylmethane (DDM) was used as a curing agent at 1:2 stoichiometric ratio. These materials were spin-coated on SS substrates and thermal-cured. TGA study indicated that both the pristine and the cured OG were more thermally stable than DGEBA. AFM study showed that the smooth surfaces of $1{\sim}2\;nm$ roughness can be prepared for both DGEBA and OG when the films were thick ($>\;1\;{\mu}$). The electrical properties such as dielectric constant, capacitance and the leakage current with respect to the applied voltage were all stable even after the stress of $100\;V/100^{\circ}C$ was applied for $0{\sim}10000$ seconds indicating that the insulating properties of DGEBA and OG films were very reliable.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.133-137
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• 2014

As a preceding process for preparing several micrometer sized Ag-coated Cu flakes, ball milling of submicrometer-sized Cu particles synthesized through a wet chemical method was performed in order to convert the particles into flakes. To suppress oxidation and aggregation of the particles during ball milling, ethylene glycol and ethyl acetate were used as a medium and a surface modifying agent, respectively. Results obtained with different rotation speeds of a jar indicated that the rotation speed changes a rotating mode, and strikingly alters the final shapes and shape uniformity of Cu particles after milling. The diameter of zirconia ball was also confirmed. Although there was aggregates in the initial submicrometer-sized Cu particles, therefore, well-dispersed Cu flakes with a size of several micrometers were successfully prepared by ball milling through optimization of rotation speed, amount of ethyl acetate, and diameter of zirconia ball.

• Journal of the Korean Magnetics Society
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• v.23 no.1
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• pp.12-17
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• 2013

Nanocrystalline nickel (Ni) tick films were synthesized by direct current electrodeposition at current density from 1 to $30mA/cm^2$ and pH = 4. The basic composition of the bath, which was prepared by dissolving Ni metal particles in HCl, was 0.2M Ni ions. The effects of the current density on the average grain size of Ni deposits were investigated by XRD and SEM techniques. The results showed that the surface roughness was decreased as the saccharin addition was increased up to 2 g/l. The experimental results showed that the increase in the current density had a considerable effect on the average grain size of the Ni deposits. The perpendicular magnetization was raised as the thickness of coating layer was increased.