• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.319-323
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• 1999

Asymmetric polyetherimide membranes were prepared by phase inversion method. In the modification of the skin layers of polyetherimide membranes, the effects of NaOH concentration on the morphology and pervaporation separation of water-isopropanol mixtures were investigated. With increasing concentration of NaOH solution, polyamicacid structure was formed by the hydrolysis of imide group of polyetherimide, and the thickness of dense layer of the asymmetric membrane increased. In the pervaporation separation of water-isopropanol mixtures the overall permeation rate decreased and the separation factor increased with increasing concentration of NaOH solution. However, when the concentration of NaOH solution was very high, the permeation rate increased but separation factor decreased. From these results, it was found that the permeation behaviors of asymmetric polyetherimide membranes depended upon the concentration of NaOH solution. These modified membranes showed that both the permeation rate and separation factor increased as the operating temperature increased.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.41 no.2
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• pp.113-119
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• 2015

The measurement of hydration level in the surface layer of the skin, stratum corneum (SC), gives important information on the biophysical properties and function of the skin barrier such as softness, flexibility, and healthiness of the skin. But it is difficult to measure a consistent hydration level from a sample to another sample due to individual variations and environmental changes. The aim of this study was to evaluate objective hydration after using various products in the SC. The SC Hydration was measured by capacitance (Corneometer$^{(R)}$, C+K, Germany) on the ventral site of forearm from 40 healthy volunteers. The skin surface was chronologically measured immediately after application of the test products and 3 and 6 hours later. We analyzed the averages of five measurements of each site and used the hydration increase rate for correction on untreated site variation. We found that most polyols including glycerol and butylenes glycol influenced directly the hydration increase rate in the SC previously. In this study, glycerol was used to prepare the standard products from 0 to 20 percents and applied to the same volunteers. The individual standard curve showed linear relation to glycerol concentrations. Based on the the standard curve, hydration of SC was converted into hydration increase rate to glycerol concentrations. The converted glycerol concentrations of products were repetitive and reproducible. In addition, the individual standard curve was used to relate the skin type of each individual. These results suggest that the hydration of the SC standardized regardless of external variation and individual skin condition can explain detailed skin state variation. Further studies will be conducted with other ingredients such as surfactants, lipids and aqueous materials, and with other methods for noninvasive measurement.

• Journal of the Korean Applied Science and Technology
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• v.31 no.3
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• pp.525-533
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• 2014

ZnO has attracted much attention such as photocatalysts, sensors, piezoelectricity and etc. At present, an economical and rapid synthesis route based on the efficient microwave polyol process is used to synthesized metal-doped ZnO nanoclusters. Diethylene glycol has a property of high polarizability, and is an excellent microwave absorbing agent, thus leading to a high heating rate and a significantly shorter reaction time. In this study, metal-doped ZnO nanoclusters are obtained with different seed volumes, when zinc acetate dihydrate is used as a precursor, and metal acetate hydrate is used as a doped-metal and diethylene glycol is used as a solvent. The obtained metal-doped ZnO nanoclusters were characterized by FE-SEM, XRD, Raman and PSA.

• Membrane Journal
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• v.25 no.1
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• pp.32-41
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• 2015

High performance polysulfone microfiltration membranes with a high were successfully prepared by vapor induced phase separation (VIPS) coupled with non-solvent induced phase separation (NIPS) process. Asymmetric Membranes were prepared with PSF/DMF/PVP/PEG/DMSO/water mixed solutions and water/IPA coagulant. PSF, DMF, PVP, PEG, DMSO, water was used as a membrane polymer, a solvent, a hydrophilic polymer additive, a polar protic liquid polymer, a polar aprotic nonsolvent, and a polar protic nonsolvent in the casting solution, respectively. The addition of polar aprotic nonsolvents, and polar protic nonsolvents is a convenient and effective method to control membrane structure. In order to control the morphology of polymeric membranes, the spontaneous emulsification induced by drawing water vapor into the exposed casting solution surface has been used. Control of the internal morphology of polymeric membranes by using mixed coagulation solution such as water and IPA is discussed in the present work. The pure water permeability, pore size distribution, surface hydrophilicity and membrane morphology were investigated. Due to the addition of DMSO to casting solution, the mean pore size increased almost $0.2{\mu}m$ and the water flux increased about 1000-1800 LMH.

• Journal of the Korean Electrochemical Society
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• v.15 no.4
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• pp.264-269
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• 2012

In this study, highly loaded(50 wt%) and very stable Pt/MWCNT catalysts for Polymer Electrolyte Membrane Fuel Cells(PEMFCs) are synthesized in short time scale by microwave assisted polyol method with different microwave irradiation time. The XRD and TEM results show that the Pt size becomes bigger as the microwave irradiation time increases. The mean Pt sizes of fabricated catalysts are 4.1, 4.9 and 8.5 nm when the microwave are irradiated for 10, 20 and 30 min, respectively. When compared with Pt catalyst made by conventional polyol method, it shows better long term durability due to the better Pt dispersion on the MWCNT surface.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.383-383
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• 2012

최근 나노 소재의 활용 가능성이 확대되어감에 따라 다양한 소재의 나노구조체에 대한 연구가 진행되어 왔다. 그 중 은(Silver)은 열전도율과 전기전도율이 가장 우수한 금속으로 다양한 형태의 은 나노 입자를 형성할 수 있고. 이를 탄소, 비석, 고분자 등의 기판에 다양한 방법으로 성장시키는 연구가 진행되었다. 기판으로 사용되는 재료 중 탄소 복합소재는 내열성, 화학적 안정성, 열전도성, 저열팽창성에 따른 치수 안정성, 유연성 등의 우수한 특징을 지니고 있으며 최근까지 방열 소재로서 활용되고 있다. 본 연구에서는 탄소섬유의 표면에 다양한 결정 구조를 가지는 Ag seed 입자를 형성하고 폴리올 공정을 통하여 와이어 형태의 나노구조체를 성장시켜 그 형상제어 특성을 FE-SEM을 통하여 확인하였다.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.515-522
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• 1999

Asymmetric polyetherimide membrane were prepared by phase inversion method, and the effects of NaOH concentration and reaction time on the morphology change of the polyetherimide membranes were studied. The morphology of skin layers varied from dense structure to sphere structure with increasing concentration of modification solution. The thickness of dense layer increased with increasing reaction time. However, when either the concentration of modifying solution was very high or the reaction time was very long, the dense layers of the asymmetric membrane were disappeared. From these results, it was found that the surface morphology of the asymmetric polyetherimide membranes depended strongly on the modification conditions such as concentration of modification solution and reaction time. These results might be explained by the hydrolysis reaction of polyetherimide into polyamic acid by the NaOH solution.

• Membrane Journal
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• v.15 no.4
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• pp.272-280
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• 2005

In this study, asymmetric polysulfone membranes were prepared by the phase inversion method and the casting solutions were containing N-methyl-2-pyrrolidone (NMP) as a solvent. Deionized water and various alcohols(methanol, ethanol, and propanol) were used as a coagulation medium in preparing asymmetric polysulfone membranes. This study investigates the effect of alcohol coagulants having different solubility parameters as a pore-former on the construction of porous structures and their pure water permeation properties. Asymmetric polysulfone membranes immersed in the pure alcohol coagulation bath solution showed the typical sponge-like structures and the reduced water permeability as compared with those of polysulfone membranes precipitated in the pure water coagulation bath solution. In the water/alcohol mixtures, asymmetric polysulfone membranes showed the finger-like structures with the sponge-like structures. Therefore, the sponge-like structure of polysulfone membrane was formed under the delayed demixing systems while the porosity of membrane was decreased significantly. The water permeability of polysulfone membrane precipitated in the pure water coagulant showed 164 [$L/m^2hr$] at 14.7 psi. In case of polysulfone membranes prepared in the pure methanol and ethanol coagulant, they showed the water permeability of 56 and 30 [$L/m^2hr$], respectively.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.669-675
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• 2009

A study has been made on the preparation of liquid resin of non-solvent and non-discoloration type for replacement of the soft PVC at room temperature. A new synthetic process was developed by structure-control design of polyurethane synthesis using pre-polymer and polyols as curing agent. The optimum recipe was made according to macro-glycols, molecular weight and reaction conditions, and the final products indicated that the mechanical properties such as tensile strength, tear strength and flexibility was very excellent than PVC products. Also, viscosity, hardness and color operations of the final products can be controlled by this system. And yellowing property by UV and NOx gas was improved from the various additive experiment.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.399-402
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• 2009

폴리올프로세스에서 PVP(Poly Vinyl Pyrrolidone) 안정제와 $NaNO_3$ 첨가제를 통해 환원속도를 조절하여 6.8 nm의 나노 큐보옥타해드론을 합성하였다. 투과전자현미경을 통해 백금 나노입자의 격자구조를 관찰하였다. 전기화학적 측정방법을 통해 백금 큐보옥타해드론 촉매가 구형의 촉매보다 우수한 촉매 성능을 나타냄을 확인하였다. 순환전류법을 통해 백금 촉매의 역방향 픽과 순방향 픽의 비율이 더 높은 것을 관찰하였다. 이것은 백금 큐보옥타해드론 촉매가 반응중 생성되는 촉매독에 강하다는 것을 의미한다. 백금 큐보옥타해드론 촉매의 표면은 {111}면과 {100}면이 혼재하며 모서리가 많이 드러나 메탄올 산화반응에 더 우수한 촉매성능을 나타내는 것으로 사료된다. 백금 촉매의 모양을 조절함으로서 백금 촉매의 표면 구조를 조절하였으며 이를 통해 높은 전류밀도를 나타내는 우수한 촉매를 합성할 수 있었다. 또한 0 ~ 0.6 V(NHE) 영역에서 촉매의 안정성을 평가한 결과 더 높은 안정성을 나타냄을 확인하였다.