• Title, Summary, Keyword: Phase separation

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Effects of Competition between Phase Separation and Ester Interchange Reactions on the Phase Behavior in a Phase-Separated Immiscible Polyester Blend: Monte Carlo Simulation

  • Youk, Ji-Ho;Jo, Won-Ho
    • Fibers and Polymers
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    • v.2 no.2
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    • pp.81-85
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    • 2001
  • The effects of rate of phase separation to ester interchange reactions and the repulsive pair interaction energy on the phase behavior in a phase-separated immiscible polyester blend are investigated using a Monte Carlo simulation method. The time evolution of structure factor and the degree of randomness are monitored as a function of homogenization time. When the phase separation is dominant over ester interchange reactions, the domain size slowly increases with homogenization time. However, when the pair interaction becomes less repulsive, the domain size does not significantly change with homogenization time. On the other hand, when ester interchange reactions are dominant over the phase separation, the homogenization proceeds without a change in the domain size. The higher the extent of phase separation, the lower the increasing rate of the DR. However, when the phase separation is sufficiently dominant, the effect of the extent of phase separation on the increasing rate of the degree of randomness become less significant.

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Structural Changes of PVDF Membranes by Phase Separation Control (상분리 조절에 의한 PVDF막의 구조 변화)

  • Lee, Semin;Kim, Sung Soo
    • Korean Chemical Engineering Research
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    • v.54 no.1
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    • pp.57-63
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    • 2016
  • Thermally induced phase separation (TIPS) and nonsolvent induced phase separation (NIPS) were simultaneously induced for the preparation of flat PVDF membranes. N-methyl-2-pyrrolidone (NMP) was used as a solvent and dibutyl-phthlate (DBP) was used as a diluent for PVDF. When PVDF was melt blended with NMP and DBP, crystallization temperature was lowered for TIPS and unstable region was expanded for NIPS. Ratio of solvent to diluent changed the phase separation mechanism to obtain the various membrane structures. Contact mode of dope solution with nonsolvent determined the dominant phase separation behavior. Since heat transfer rate was greater than mass transfer rate, surface structure was formed by NIPS and inner structure was by TIPS. Quenching temperature of dope solution also affected the phase separation mechanism and phase separation rate to result in the variation of structure.

Chiral Separation of Tryptophan Enantiomers by Liquid Chromatography with BSA-Silica Stationary Phase

  • Kim Kwonil;Lee Kisay
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.5 no.1
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    • pp.17-22
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    • 2000
  • The separation of tryptophan enantiomers was carried out with medium-pressure liquid chromatography using BSA (bovine serum albumin)-bonded silica as a chiral stationary phase. The influence of various experimental factors such as pH and ionic strength of mobile phase, separation temperature, and the presence of organic additives on the resolution was studied. In order to expand this system to preparative scale, the loadability of sample and the stability of stationary phase for repeated use were also examined. The separation of tryptophan enantiomers was successful with this system. The data indicated that a higher separation factor (a) was obtained at a higher pH and lower temperature and ionic strength in mobile phase. Addition of organic additives (acetonitrile and 2-propanol) in mobile phase contributed to reduce the retention time of L-tryptophan. About $30\%$ of the separation factor was reduced after 80 days of repeated use.

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Phase Separation and their Structures in $BaO-B_2O_3$ Glasses ($BaO-B_2O_3$계 유리의 상분리 현상과 유리의 구조)

  • 채수철;김철영
    • Journal of the Korean Ceramic Society
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    • v.23 no.6
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    • pp.25-32
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    • 1986
  • Phase spearated glass is heterogeneous in microscopic point of view and the heterogeneities affect the structures of glasses. In the present work the phase separation of $BaO-B_2O_3$ glass system was investigated and the effect of $P_2O_5$ on the phase separation and crystallization was also studied in the above system. Experiments such as scanning electron microscopy X-ray diffraction and infrared spectroscopy were performed. Phase separation with $B_2O_3$ rich phase matrix and BaO rich phase droplet was observed for the glasses containing less than 6 mole% of BaO while the opposite morphology of phase separation was found for the glasses containing more than 7 mole% of BaO. Phase separation region was extended up to the glass with 22mole% of BaO when the amount of $P_2O_5$ was increased. The heat-treated glasses crystallized to BaO.$4B_2O_3$$P_2O_5$ hindered the glass from the crystalli-zation.

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Effect of Liquid Crystal Structures on olymerization-induced Phase Separation Behavior by Simultaneous Resistivity and Turbidity Measurement

  • Park, Su-Cheol;Lee, Sang-Sub;Hong, Jin-Who
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.886-889
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    • 2007
  • Photopolymerization and phase separation behavior during the PDLC formation process were investigated by simultaneous resistivity and turbidity measurement. Using this experimental method, we investigated the effect of liquid crystal structure on photopolymerization and phase separation behavior.

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Morphology of Silk Fibroin/Poly(vinyl alcohol) Blend Film (견피브로인/Poly(vinyl alcohol) 브렌드 필름의 형태학적 구조)

  • 엄인철;박영환
    • Journal of Sericultural and Entomological Science
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    • v.40 no.2
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    • pp.169-175
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    • 1998
  • The morphology of silk fibroin/poly(vinyl alcohol)(PVA)blend films was investigated using optical microscopy and confocal laser scanning microscopy. The effects of blend ratio and molecular weight of silk fibroin and PVA on phase separation were studied. Macro-phase separation occurred for the silk fibroin-rich/poor region whereas micro-phase separation took place for the dispersed/continuous phase, In spite of differences in molecular weight and blend ratio, it is observed that the dispersed phase and continuous one are composed of silk fibroin and PVA component, respectively. As the molecular weight of silk fibroin and silk fibroin content in blend ratio are decreased, the compatibility of blend is increased due to the reduction of micro-phase separation.

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Preparation of PVDF Membrane by Thermally-Induced Phase Separation

  • Heo, Chi-Haeng;Lee, Kyung-Mo;Kim, Jin-Ho;Kim, Sung-Soo
    • Korean Membrane Journal
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    • v.9 no.1
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    • pp.27-33
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    • 2007
  • PVDF membrane formation via TIPS was performed for PVDF/DBP and PVDF/DMP systems. PVDF/DBP system showed solid-liquid phase separation behavior, while PVDF/DMP system has liquid-liquid phase separation characteristic as well as solid-liquid phase separation characteristic. PVDF contents and cooling conditions had great influence on structure, and the effects of each parameter were examined. Spherulitic structure was obtained due to the dominant PVDF crystallization. Diluent rejected to the outside of spherulite occupied the surface of the PVDF spherulites to result in the microporous spherulite formation and micro-void between spherulites. PVDF/DMP system had competitive solid-liquid and liquid-liquid phase separation depending on the cooling path.

Analysis of Phase Separation by Thermal Aging in Duplex Stainless Steels by Magnetic Methods

  • Kim, Sunki;Wonmok Jae;Kim, Yongsoo
    • Nuclear Engineering and Technology
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    • v.29 no.5
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    • pp.361-367
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    • 1997
  • The phase separation in ferrite phase of duplex stainless steel is the primary cause of thermal aging embrittlement of the LWR primary pressure boundary components. In this study the phase separation of simulated duplex stainless steel was detected by Mossbauer spectroscopy and magnetic property analysis by VSM(Vibrating Specimen Magnetometer). The simulated duplex stainless steels, Fe-Cr binary, Fe-Cr-Ni ternary, and Fe-Cr-Ni-Si quarternary allots, were aged at 370 and 40$0^{\circ}C$ up to 5,340 hours. It was observed from Mossbauer spectra analysis that internal magnetic field increases with aging time and from VSM that the specific saturation magnetization and Curie temperature increase with aging time. These result are indicative that phase separation into Fe-rich region and Cr-rich region is caused by thermal aging in the temperature range of 370~40$0^{\circ}C$ In cases of specimens containing Ni, the increase of specific saturation magnetization is much higher. This implies that Ni seems to promote Fe-Cr interdiffusion, which accelerates the phase separation into Fe-rich $\alpha$ phase and Cr-rich $\alpha$' phase.

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The Phase Separation of Mixed Solutions with Ethanol and Gasoline (에탄올과 가솔린 혼합상에 대한 상분리 현상)

  • Lee, Jin-Hui;Kim, Mi-Hyun;Lee, Jin-Hee;Ahn, Moon-Sung;Won, Jin-Ok;Han, Geu-Seong;Seo, Dong-Ho
    • Journal of the Korean Applied Science and Technology
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    • v.24 no.1
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    • pp.86-91
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    • 2007
  • Gasohol, which is combined solution of gasoline and ethanol, is difficult to apply to the field, because it usually brings phase separation by mingling of water. We investigated phase separation by adding different concentrations of "Ethanol", anhydrous and fermentative, to "Gasolines", gasoline, gasoline base and naphtha, Placing ethanol itself open to the air, the concentrations of water are increased in length of time. The phase separation temperatures of the gasolines-ethanol solutions have dropped in the following order : gasoline, gasoline base and naphtha. When adding water to the solutions of gasolines and anhydrous ethanol, the temperatures of phase separation is higher when the concentration of water increases more. Thus, it is obvious that the water is sensitive in phase separation.

Phase Separation of Matrix Glasses and Precipitation Characteristics of CuCl Nanocrystals in CuCl Doped Borosilicate Glasses for Nonlinear Optical Application (CuCl 미립자 분산 붕괴산염계 비선형 광학유리에서 매질유리의 상분리와 CuCl 미립자의 석출 특성)

  • 윤영권;한원택
    • Journal of the Korean Ceramic Society
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    • v.34 no.8
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    • pp.886-896
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    • 1997
  • To investigate an effect of phase separation on precipitation characteristics of CuCl nanocrystals in CuCl doped nonlinear optical glasses, borosilicate glass systems with 9 different compositions with ~2wt% of CuCl were selected and CuCl doped glasses were prepared by melting and precipitation method. Microstructural properties of the CuCl doped glasses were analyzed by optical absorption spectroscopy, acid elution test, TEM, and EDXS. While phase separation did not occur in Glass A~D, interconnected and droplet microstructures due to phase separation were found in Glass E, F and Glass G~I, respectively. In the particular composition of the matrix glasses in this study, the precipitation of the CuCl particles was observed in the phase separable glasses, not in phase non-separable glasses. The CuCl particles were precipitated in both silica-rich phase region and boronrich phase region of the glass matrix. In the case of 7.7Na2O-36.6B2O3-52.7SiO2(mole%) glass, the larger CuCl particles than those in the silica-rich phase region were observed in the boron-rich phase region.

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