• Membrane Journal
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• v.15 no.1
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• pp.62-69
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• 2005

SEBS-clay hybrid membranes were prepared by melt intercalation method with internal mixer. In the hybrid, the amount of clay content was fixed to 5 phr. MMT was intercalated or exfoliated by the ionomer and it was confirmed by X-ray diffraction method. D-spacing of the characteristic peak from MMT plate in SAXD was moved and diminished. Gas permeability, mechanical properties and thermal properties of the SEBS-clay hybrid membranes were investigated. Gas permeability through the SEBS-clay hybrid membranes decreased due to increased tortuosity made by intercalation of clay in SEBS.

• Membrane Journal
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• v.24 no.4
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• pp.325-331
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• 2014

We synthesized novel polyimides with high gas permeability and selectivity for application of on board inert gas generation system (OBIGGS). 2,2-bis(3,4-carboxylphenyl) hexafluoropropane dianhydride (6FDA) and two kinds of amines with high permeability and solubility were used to prepare the novel polymide. 2,3,5,6-Tetramethyl-1,4-phenylenediamine (TMPD) was used to improve gas permeability and various kinds of diamines were used to improve the gas selectivity respectively. The polyimide copolymers were synthesized by commercial chemical imidization method and their average molecular weights were over 100,000g/mol. The glass temperature ($T_g$) and the thermal degradation temperature were characterized using differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The synthesized copolymers showed high $T_g$ over $300^{\circ}C$ and high thermal degradation temperature over $500^{\circ}C$. The gas permeation properties were measured by time-lag equipment. Although general polyimides showed very low gas permeability, synthesized polyimide copolymer showed high $O_2$ permeability of 36.21 barrer with high $O_2/N_2$ selectivity around 4.1. From this result, we confirm that these membranes have possibility to apply to OBIGGS.

• Journal of Life Science
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• v.27 no.1
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• pp.15-22
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• 2017

Streptococcus mutans (S. mutans), which plays a major role in the etiology of human dental caries, is able to tolerate exposure to acid shock in addition to its acidogenicity. We investigated the effects of pH stress on membrane fluidity, activities and expression levels of F-ATPase, and proton permeability in S. mutans. Using 1,6-diphenyl-1,3,5-hexatriene, we observed membrane ordering at pH 4.8 and pH 8.8. The ordering effects were larger at pH 4.8 in cytoplasmic membranes isolated from S. mutans (CMSM). Increasing pH resulted in a decrease in the activities and expression levels of F-ATPase. The proton permeability was decreased at both acidic and alkaline pHs, and the lowest permeability was observed at pH 4.8. The lower permeability at pH 8.8 than pH 6.8 is likely to be caused by the decreased proton influx due to the decreased CMSM fluidity. In addition, it seems to be evident that extremely low permeability at pH 4.8 was caused by the decreased proton influx due to the decreased CMSM fluidity as well as the increased proton efflux due to the increased activity and expression level of F-ATPase. It is likely that CMSM fluidity and F-ATPase activity are two major key factors that determine proton permeability in S. mutans. We suggest that CMSM fluidity plays an important role in the determination of proton permeability, which sheds light on the possibility of using nonspecific membrane fluidizers, e.g., ethanol, for anti-caries purposes.

• Membrane Journal
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• v.30 no.1
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• pp.46-56
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• 2020

In this study, poly (ether-block-amide) (PEBAX)/poly (ethylene) glycoldiacrylate (PEGDA)/zeolitic imidazolate framework-8 (ZIF-8)-polyethersulfone (PES) composite membranes were prepared. The gas permeation properties of N₂ and CO₂ were investigated for each composite membrane. First, the gas permeability in the PEBAX/PEGDA-PES composite membrane decreased with increasing PEGDA content for each molecular weight at PEGDA250, PEGDA575, and PEGDA-700 g/mol. The CO₂/N₂ selectivity showed a constant value and gradually increased with increasing PEGDA content after 30 wt% PEGDA, and PEBAX/PEGDA250 50 wt%-PES prepared by adding PEGDA250 g/mol 50 wt% showed a selectivity of 15.1. This is because as the PEGDA content increases, the number of diacrylate groups increases, and the CO₂ affinity due to the ether structure of PEGDA increases. Gas permeation properties according to ZIF-8 were investigated for composite membranes of PEGDA 0 to 30 wt%, with CO₂/N₂ selectivity almost constant for each molecular weight. The permeability of N₂ and CO₂ gradually increased with increasing ZIF-8 content, and CO₂/N₂ selectivity was the highest at 3.4 in PEBAX/PEGDA250 g/mol 30 wt%/ZIF-8 20 wt%-PES composite membrane.

• Membrane Journal
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• v.33 no.6
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• pp.325-343
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• 2023

Direct methanol fuel cells (DMFCs) have been attracting attention as energy conversion devices that can directly supply methanol liquid fuel without a fuel reforming process. The commercial polymer electrolyte membranes (PEMs) currently applied to DMFC are perfluorosulfonic acid ionomer-based PEMs, which exhibit high proton conductivity and physicochemical stability during the operation. However, problems such as high methanol permeability and environmental pollutants generated during decomposition require the development of PEMs for DMFCs using novel ionomers. Recently, studies have been reported to develop PEMs using hydrocarbon-based ionomers that exhibit low fuel permeability and high physicochemical stability. This review introduces the following studies on hydrocarbon-based PEMs for DMFC applications: 1) synthesis of grafting copolymers that exhibit distinct hydrophilic/hydrophobic phase-separated structure to improve both proton conductivity and methanol selectivity, 2) introduction of cross-linked structure during PEM fabrication to reduce the methanol permeability and improve dimensional stability, and 3) incorporation of organic/inorganic composites or reinforcing substrates to develop reinforced composite membranes showing improved PEM performances and durability.

• Membrane Journal
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• v.24 no.5
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• pp.358-366
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• 2014

Chitosan-HNT (halloysite nanotube) composite membranes were prepared by the addition of HNT 0, 3, 5, and 10 wt%. The structure of composite membranes were studied by FT-IR, XRD, TGA, and SEM. Gas permeation experiment were performed under condition of $30^{\circ}C$ and $4kgf/cm^2$. Gas permeability and selectivity were investigated by increasing the amount of HNT contents in the chitosan. Chitosan-HNT composite membrane for $CO_2$ and $CH_4$ showed the maximum value at 3 wt% of HNT content and decreased thereafter. The selectivity of ($CO_2/CH_4$) was increased due to its affinity with the OH groups on the HNT, was shown in the range of 1.3 to 3.8 at 0~10 wt%.

• Membrane Journal
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• v.11 no.1
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• pp.38-49
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• 2001

The surface of polyimide membrane was modified by plasma treatment using Ar and NH~. and the permeability and selectivity for the mixture gas $(CO_2/N_2=20/80 vol%)$ were measured. The per¬meation experiments were performed by a variable volume method at $30^{\circ}$C and total pressure of 5 atm, The effect of the plasma conditions such as treatment time, power input, gas flow rate and pressure in the reactor on the transport Dwperties of modified membranes was investigated. The surface of the plasma treated membrane was analyzed by means of FTlR - ATH, ESCA and AFM. The dependences of the wettability and the etching on plasma treatment time were investigated by use of the contact angle and the weight loss measurement. Measurements of gas pcnneability characteristic were performed using both dry and wet membranes. The effects of experimental conditions such as temperature on the membrane performance were studied.

• Membrane and Water Treatment
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• v.4 no.1
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• pp.27-51
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• 2013

During cleaning steps, ultrafiltration membranes are mechanically and chemically stressed. This may result in membrane degradations and failures. In this paper, polysulfone membranes were used to evaluate membrane deteriorations by commercial detergents in static conditions. Ageing of the membrane was simulated by immersing samples in solutions containing commercial detergents with various concentrations, temperatures and times defined by experimental designs. Indeed, an innovative approach in the chemical membranes ageing researches, based on methodological tools, was used in order to achieve significant ageing experiments without using an accelerated ageing protocol. The macroscopic changes were monitored by permeability measurements and mechanical strength tests coupled with a microscopic characterization by ATR-FTIR and HRSEM. The present work details results obtained for three commercial detergents: an alkaline, an acidic and an enzymatic detergent. It was found that the detergents used in the industrial advised conditions (concentration, temperature and time of contact) were not detrimental for membrane properties (permeability and elongation at break) and so for the quality of the produced water. Over the industrial cumulated time of contact, different ageing effects can be observed and compared with the ones induced by NaOCl.

• Membrane Journal
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• v.24 no.3
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• pp.177-184
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• 2014

Silica membranes with high permeability were prepared using colloidal and polymeric silica sols on a porous stainless steel-tube support by a DRFF and SRFF method. Silica sols were derived with tetraethylorthosilicate (TEOS) by sol-gel method and analyzed with DLS, FE-SEM, and $N_2$ adsorption. The coating of the intermediate layer with colloidal silica sol on the stainless steel-tube support led to a denser surface morphology of the membrane along with a considerable reduction in the number of surface defect. As the polymeric silica sol enclosed the colloidal silica sol with spherical particles during the SRFF method, the separation-layer-coated silica membrane showed a denser surface than the intermediate layer. Moreover, the silica membranes showed high hydrogen gas permeability of $(6.63-9.21){\times}10^{-5}mol{\cdot}m^{-2}{\cdot}s^{-1}{\cdot}Pa^{-1}$ with low $H_2/N_2$ perm-selectivity (2.9-3.1) at room temperatures.

• Membrane Journal
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• v.24 no.6
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• pp.438-447
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• 2014

The amorphous and porous borosilicate without any cracks was obtained under the following condition : 0.01~ 0.10 mole ratio of trimethylborate (TMB)/ tetraethylorthosilicate (TEOS) and the temperature of $700{\sim}800^{\circ}C$. According to the BET and SEM measurements, borosilicate heat-treated in between 700 and $800^{\circ}C$ showed the surface area of $251.12{\sim}355.62m^2/g$, the pore diameter of 3.5~4.9 nm, and the particle size of 30~60 nm. According to the TGA measurements, the thermal stability of poly[1-(trimethylsilyl)propyne](PTMSP) membrane was enhanced by inserting borosilicate. SEM observation showed that the size of dispersed borosilicate in the composite membrane was $1{\mu}m$. The results showed that the permeability of $H_2$ and $N_2$ increased and the selectivity of $H_2/N_2$ decreased upon the addition of borosilicate into PTMSP membranes. Addition of borosilicate may possibly increase the free volume, cavity and porosity of membranes indicating that permeation occurred by molecular sieving, surface and Knudsen diffusion rather than solution diffusion of gases.