(A) study on the mechanism of membrane formation from Polysulfone/NMP/water system by means of phase inversion = 폴리술폰/NMP/물 시스템으로부터 상전이법에 의해 제조된 분리막의 형성 기구에 대한 연구

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Thermodynamics and kinetics of membrane forming polysulfone (PSf)/NMP/Water system was studied and membrane morphologies and related phase separation behavior was also investigated. The cloud point curves for ternary systems of PSf/THF/water and PSf/NMP/water were determined by a titration method at 15℃, 30℃, 45℃ and 60℃. A small amount of water (3~10 wt% water) was needed to achieve liquid-liquid phase separation in both systems and the temperature effect was small. From numerical calculation, it was found that the binary interaction parameters for the PSf/solvent/water system enlarges the homogeneous region in phase diagram with a smaller $\chi_{13}, a greater $\chi_{12}$, and a smaller $\chi_{23}$ and the effect of polymer molecular weight was negligible except in the range of low molecular weight. The slope of the tie lines indicated that demixing of the ternary system occurred at relatively similar nonsolvent concentration in both phases. We obtained a value of 2.7 for the water-PSf interaction parameter by fitting the experimental cloud point curve with the calculated binodal lines. We formulated ternary diffusion equations relating chemical potential gradients in the polymer film with friction coefficients between components, and obtained the diffusion trajectory in the phase diagram. In the present calculation, instead of equilibrium interfacial boundary conditions, we use new boundary conditions including mass transfer coefficient. By doing this, we could demonstrate the possible spinodal decomposition mechanism in case of instantaneous demixing. The vitrification line for the ternary system of PSf/NMP/water was determined by a DSC measurement with varying the compositions. The vitrification composition was 72.0 wt % of polysulfone and 28.0 % of solvent at 15℃ and 79.8 wt % of polysulfone and 20.2 % of solvent at 60℃, respectively. We also found that the slope of the vitrification line changed with temperature and it was steep in the case of higher...
Advisors
Kim, Sung-Chulresearcher김성철researcher
Description
한국과학기술원 : 화학공학과,
Publisher
한국과학기술원
Issue Date
1999
Identifier
150186/325007 / 000955075
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 화학공학과, 1999.2, [ xiii, 141 p. ]

Keywords

Mass transfer; Cloud point; Phase separation; Polysulfone membrane; Vitrification; 유리화; 물질전달; 흐림점; 상분리; 폴리술폰막

URI
http://hdl.handle.net/10203/28805
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=150186&flag=dissertation
Appears in Collection
CBE-Theses_Ph.D.(박사논문)
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