• Title/Summary/Keyword: nonsolvent induced phase separation

Search Result 17, Processing Time 0.028 seconds

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

  • Lee, Semin;Kim, Sung Soo
    • Korean Chemical Engineering Research
    • /
    • v.54 no.1
    • /
    • pp.57-63
    • /
    • 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.

Preparation of Asymmetric Membranes by Addition of Nonsolvent (비용매 첨가제를 이용한 비대칭막의 제조)

  • Kim, Nowon
    • Membrane Journal
    • /
    • v.25 no.1
    • /
    • pp.32-41
    • /
    • 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.

Effect of Addition of Cosolvent γ-Butyrolactone on Morphology of Polysulfone Hollow Fiber Membranes (폴리설폰 중공사막 구조에 대한 조용매 γ-Butyrolactone 첨가 영향)

  • Yun, Sukbok;Lee, Yongtaek
    • Applied Chemistry for Engineering
    • /
    • v.25 no.3
    • /
    • pp.274-280
    • /
    • 2014
  • Polysulfone (PSf) hollow fiber membranes were prepared via the nonsolvent induced phase separation technique. The cosolvent of ${\gamma}$-butyrolactone (GBL) was added to the polymer solution containing a mixture of PSf and N,N-dimethylacetamide (DMAc). Water was utilized as a precipitation nonsolvent. The morphology of prepared membranes was investigated using a field emission scanning electron microscopy. The fabricated membrane showed a typical asymmetric structure such as the dense layer on the porous support layer by the addition of GBL to the polymer solution. As the concentration of GBL increased, the asymmetric porous structure was shown to be more intensified. It was thought that the added GBL played a role of enhancing the liquid-liquid phase separation of the polymer solution, since the cosolvent of GBL might change the thermodynamic solubility parameter of the doping solution. Permeation properties through the prepared hollow fiber membranes were characterized by measuring the pure water flux and the solute rejection using $0.05{\mu}m$ polystyrene latex (PSL) beads. Experimental results revealed that the use of PEG as the internal coagulant enhanced the pure water flux up to 130 times compared to the use of EG while the rejection of the PSL beads decreased only 5%.

Effect of Toluene Added to Casting Solution on Characteristic of Phase Inversion Polysulfone Membrane (상전환 공정에 의한 폴리설폰막의 제조에 있어 제막용액에 첨가된 톨루엔의 영향)

  • Choi, Seung-Rag;Park, So-Jin;Seo, Bum-Kyoung;Lee, Kune Woo;Han, Myeong-Jin
    • Applied Chemistry for Engineering
    • /
    • v.19 no.6
    • /
    • pp.633-639
    • /
    • 2008
  • Polysulfone membranes were prepared via the phase inversion process. Toluene was added as a nonsolvent additive in the casting solution containing a mixture of polysulfone and n-methylpyrrolidone. When prepared via the diffusion-induced process using isopropanol as a precipitation nonsolvent, the solidified membranes revealed a similar asymmetric structure irrespective of the addition of toluene, presenting both a dense skin layer and a sponge-like support layer. The added toluene played a role of enhancing liquid-liquid phase separation of the casting solution, and skin layer thickness of a prepared membrane increased with toluene content in the casting solution. On membrane performance, the solute rejection showed a uniform behavior irrespective of the addition of toluene. However, in spite of the significant increase in dense skin layer thickness, the water permeation through the membrane prepared with 60 wt% toluene revealed five times as much flux, compared with that of the membrane prepared without toluene additive.

Anisotropic Acorn-like Particle Fabrication Via a Dynamic Phase Separation Method (동적 상분리법을 이용한 이방성 도토리형상 입자 제조)

  • Park, Chul Ho;Baek, Il-hyun
    • Membrane Journal
    • /
    • v.29 no.1
    • /
    • pp.61-65
    • /
    • 2019
  • Anisotropic particles have been issued in various fields due to their unique physical properties. Herein, a novel dynamic phase separation method (DPS) is introduced to fabricate anisotropic acorn-like nanoparticles. DPS consists of two dynamic conditions; solvent evaporation and nonsolvent induced precipitation. The bottom layer is controlled by feeding the water as a non-solvent diluent, and the phase separation of the upper layer relies on the diffusion and evaporation of a volatile good solvent. At this condition, the acorn-like particles were fabricated. Under a closed box filled with water (spontaneous phase separation), monodisperse polystyrene (PS) particles were synthesized. At the coexistence between DPS and spontaneous phase separation, the sizes of cap and particle were changed. Also, the volume of PS solutions influences on the particle shape. Since the unique structures could be utilized into various applications, if advanced techniques such as membrane-based controlled water feeding is developed, monodisperse acorn-like particles could be tuned.

Characterization and Preparation of PEG-Polyimide Copolymer Asymmetric Flat Sheet Membranes for Carbon Dioxide Separation (이산화탄소 분리를 위한 폴리에틸렌글리콜계 폴리이미드 공중합체 비대칭 평판형 분리막의 제조 및 기체 투과 특성평가)

  • Park, Jeong Ho;Kim, Deuk Ju;Nam, Sang Yong
    • Membrane Journal
    • /
    • v.25 no.6
    • /
    • pp.547-557
    • /
    • 2015
  • In this study, we synthesized polyimide with high carbon dioxide gas transport property using 2,2-bis(3,4-carboxylphenyl) hexafluoropropane, 2,3,5,6-tetramethyl-1,4-phenylenediamine and poly(ethylene glycol) bis(3-aminopropyl) terminated and then we calculated solubility parameter of synthesized polymer and non-solvent phase separation coefficient to determine proper solvent for preparation of asymmetric membrane, also we measured the viscosity of the polymer solution to check polymer contents in membrane solution and prepare asymmetric membrane with $LiNO_3$ additives. The morphology and gas separation property of membrane prepared by phase separation method was confirmed using Field Emission Scanning Electron Microsope and the single gas permeation measurement apparatus. We confirmed that the carbon dioxide permeance of the membrane increased and the selectivity showed little change with decreasing of the volatile solvent contents.

Controlling the Morphology of Polyvinylidene-co-hexafluoropropylene (PVDF-co-HFP) Membranes Via Phase Inversion Method (상전이법을 이용한 P(VDF-co-HFP) 분리막 구조제어)

  • Song, Ye Jin;Kim, Jong Hoo;Kim, Ye Som;Kim, Sang Deuk;Cho, Young Hoon;Park, Ho Sik;Nam, Seung Eun;Park, You In;Son, Eun Ho;Kim, Jeong F.
    • Membrane Journal
    • /
    • v.28 no.3
    • /
    • pp.187-195
    • /
    • 2018
  • In this work, the morphology of polyvinylidene-co-hexafluoropropylene (PVDF-co-HFP) membranes were systemically investigated using phase inversion technique, to target membrane contactor applications. As the presence of macrovoids degrade the mechanical integrity of the membranes and jeopardize the long-term stability of membrane contactor processes (e.g. wetting), a wide range of dope compositions and casting conditions was studied to eliminate the undesired macrovoids. The type of solvent had significant effect on the membrane morphology, and the observed morphology were correlated to the physical properties of the solvent and solvent-polymer interactions. In addition, to fabricate macrovoid-free structure, the effects of different coagulation temperatures, inclusion of additives, and addition of nonsolvents were investigated. Due to the slow crystallization rate of P(VDF-co-HFP) polymer, it was found that obtaining porous membrane without macrovoids is difficult using only nonsolvent-induced phase separation method (NIPS). However, combined other phase inversion methods such as evaporation-induced phase separation (EIPS) and vapor-induced phase separation (VIPS), the desired membrane morphology can be obtained without any macrovoids.

Characterization and Preparation of Polyimide Copolymer Membranes by Non-Solvent Induced Phase Separation Method (비용매 유도 상전이법을 이용한 공중합체 폴리이미드 분리막의 제조 및 특성평가)

  • Lee, Jung Moo;Park, Jeong Ho;Kim, Deuk Ju;Lee, Myung Gun;Nam, Sang Yong
    • Membrane Journal
    • /
    • v.25 no.4
    • /
    • pp.343-351
    • /
    • 2015
  • In this study, we synthesis polyimide with high gas selectivity using 2,2-bis(3,4-carboxylphenyl) hexafluoropropane, 2,4,6-Trimethyl-1,3-phenylenediamine (DAM) and 4,4-Methylenedianiline (p-MDA), and then the asymmetric membrane was fabricated by non-solvent phase separation method. To confirm the property change of the membrane using different solvent, we measured and compared the viscosity of the polymer solution, cloud point and non-solvent phase separation coefficient. The morphology and gas separation property of membrane prepared by phase separation method was confirmed using Field Emission Scanning Electron Microsope and the single gas permeation measurement apparatus. The single gas ($CH_4$, $N_2$, $O_2$, $CO_2$) permeation property and selectivity value of the membrane prepared with NMP was higher than the membrane prepared with DMAc. We confirmed that the gas selectivity of the membrane increased and the permeation property decreased with increasing of the solvent evaporation time.

Effect of Nonwoven Support During Fabrication of Flat Sheet Membranes via Phase Inversion Method (상전이법 기반 평막 제조과정에서 부직포 영향 분석연구)

  • Kim, Minjae;Kim, Subin;Kim, Sumin;Lee, Hoik;Kim, Jeong F.
    • Membrane Journal
    • /
    • v.32 no.2
    • /
    • pp.109-115
    • /
    • 2022
  • In this work, the effect of nonwoven support during fabrication of flat sheet membranes via nonsolvent-induced phase separation, was investigated in detail. It was found that dope solutions with low viscosity tend to penetrate through the nonwoven support during phase inversion, resulting in nonhomogeneous membranes. A simple soaking treatment of nonwoven support prevented such unwanted dope penetration, and resulted in membranes with higher water and solvent permeance performance. The dope penetration through nonwoven was more prominent in solutions with low viscosity, and the nonwoven soaking treatment not effective in solutions with high viscosity.

Solvent Filtration Performance of Thin Film Composite Membranes based on Polyethersulfone Support (폴리이터설폰 지지체를 활용한 박막복합막의 용매투과특성 연구)

  • Kim, SeungHwan;Kim, YooShin;Kim, DoYong;Kim, SooMin;Kim, Jeong F.
    • Membrane Journal
    • /
    • v.29 no.6
    • /
    • pp.348-354
    • /
    • 2019
  • Recently, the application range of organic solvent nanofiltration (OSN) technology has been expanding, requiring membranes with better performance. In this work, thin film composite (TFC) OSN membrane was fabricated. First, ultrafiltration support membrane was prepared via nonsolvent-induced phase separation (NIPS) technique using polysulfone (PSf) and polyethersulfone (PES). Then, the effect of pore forming additives such as polyvinylpyrrolidone (PVP) and pluronic F-127 were employed to improve the membrane permeance. The well-known interfacial polymerization technique was employed using MPD-TMC chemistry to form a thin film on top of the fabricated support, and its solvent permeance and nanofiltration performance was characterized. It was found that polyethersulfone support exhibited more reliable performance compared to polysulfone, and PVP additive was more effective compared to Pluronic F-127. As for the oSN performance, polar aprotic solvents like acetonitrile show significantly higher flux (986.5 L·m-2·h-1·bar-1) compared to water and EtOH (9.5 L·m-2·h-1·bar-1).