• Membrane Journal
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• v.12 no.4
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• pp.247-254
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• 2002

In order to develop the ion exchange membranes which would be used in direct methanol fuel cell (DMFC), the polysulfone polymer was sulfonated using chlorosulfonic acid (CSA) and trimethylchlorosilane(TMCS). It has been characterized in terms of ion conductivities, methanol crossover, swelling degree and ion exchange capacities for the heat untreated and treated membranes at $150^{\circ}C.$ Typically, the methanol permeability and ion conductivity at the mole ratio of 1.4 between polysulfone repeating unit and sulfonating agents showed $2.87{\times}10^{-7}\; cm^2/s$(without heat treatment), $1.52{\times}10^{-7}\; cm^2/s$(with heat treatment) and $1.10{\times}10^{-2}\; S/cm$(without heat treatment), $0.87{\times}10^{-2}\;$ S/cm(with heat treatment), respectively. After the mole ration of 1.4 both values indicated mild increase.

• Journal of the Korean Institute of Gas
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• v.5 no.1
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• pp.29-36
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• 2001

The permeation properties of $O_2\;and\;N_2$ were measured for bromobisphenol A polysulfone(BPSf), bisphenol A trimethylsilylated polysulfone(TMSPSf) and their blend membrane to investigate the structure-properties relationships. BPSf shows relatively high permselectivity. It can be explained that the strong polarity of bromine in BPSf increases chain packing ability. In this case the distance of polymer chains is reduced by increasing of interchain interaction by induced dipole. TMSPSf shows relatively high permeability. The higher value of permeability coefficients for TMSPSf is due to the substitution of very bulky trimethylsilyl groups. The replacement of phenyl hydrogens of bisphenol A polysulfone(PSf) with trimethylsilyl groups results in higher fractional free volume(FFV). In this work, taking into account the complimentary features of BPSf and TMSPSf, BPSf/TMSPSf blend was prepared and the compatibility in mixing are examined. The BPSf/TMSPSf blend shows higher permeability than commercial PSf, with minimum loss of selectivity. The miscibility of the BPSf/TMSPSf blend is confirmed by the single glass transition temperature.

• Membrane Journal
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• v.20 no.2
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• pp.135-141
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• 2010

Various asymmetric Polysulfone membranes were prepared for a MBR process. Ether-typed alcohols (co-solvent) were added into a dope solution in order to control the pore size of membrane, whose effect on water permeability were investigated. Pore size of the prepared membranes were more affected by molecular-structure of co-solvent than by boiling point of theirs. With the increasing order of methoxy ($CH_3$-O-) < secondary propanol ($-CH_2$-CH(OH)$-CH_3$) < ethoxy ($CH_3-CH_2$-O-), water permeability of the prepared membrane increased. The phenomenon might attribute to the difference of molecularly steric hinderance of co-solvent (eg, Methoxy propanol, Ethoxy ethanol, Methoxy ethanol) in dope solution during the phase inversion. By the addition of ether typed alcohol into a dope solution, the pore size of MF (microfiltration) could be controlled. Also, Membrane prepared was applied to a MBR process and the system was stably operated for 2 months.

• Membrane Journal
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• v.18 no.4
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• pp.317-324
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• 2008

Polysulfone membranes were prepared via the phase inversion process. With propionic acid as a nonsolvent additive, polysulfone casting solutions were solidified in an isopropanol bath. Propionic acid (PA) worked as a thermodynamic enhancer for phase separation and as a rheological suppressor for kinetic hindrance. Morphology of the prepared membranes significantly varied with propionic acid content in the casting solution. The dense skin layer, which was identified in the membrane prepared without PA, almost disappeared in the membrane prepared trom PA 10wt%. With 30wt% PA, the membrane revealed the morphological gradient from a nodular skin structure to a sponge-like substructure, including the finger-like cavity. Water permeability increased with PA content, and polyethylene glycol rejection decreased with the nonsolvent content.

• Applied Chemistry for Engineering
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• v.19 no.6
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• pp.633-639
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• 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.

• Membrane Journal
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• v.24 no.1
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• pp.50-62
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• 2014

An asymmetric microfiltration membranes were prepared with polysulfone by an immersion precipitation phase inversion method. Microfiltration membranes were prepared by polysulfone/N-methyl-2-pyrrolidone/polyvinylpyrrolidone/phosphoric acid casting solution and water coagulant. The vapor induced phase inversion method was used to prepare the membranes. The pore size and the morphology were changed by the phosphoric acid additive, the temperature of casting plate and the exposure time at the relative humidity of 74%. The morphology of membranes was investigated by scanning electron microscopy and microflow permporometer. By the addition of the phosphoric acid additive in the casting solution, the morphology of the prepared membranes were changed from a dense sponge structure to a loose asymmetric sponge structure. Due to the addition of catalytic amount of phosphoric acid to NMP casting solution, the mean pore size increased almost $0.2{\mu}m$ and the water flux increased about 3,000 LMH. The temperature of casting plate and exposure time had a apparent effect on the skin layer structure and the pore size and the porosity of the membrane.

• Polymer(Korea)
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• v.25 no.2
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• pp.177-185
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• 2001

In this work, the cure kinetics and rheological properties of difunctional epoxy(diglycidylether of bisphenol A, DGEBA)/polysulfone (PSF) blends were investigated using differential scanning calorimeter and rheometer. From the DSC results of the blends, the temperature of the exothermic peak and cure activation energy (E) using a half-width method were increased with increasing the PSF content to neat epoxy resin up to 30 wt%. However, a marginal decrease in the blend system was shown in E. The conversion ($\alpha$) and conversion rate (d$\alpha$/dt) were decreased as the content of PSF increases. Rheological properties of the blend system were investigated under isothermal condition using a rheometer. Cross-linking activation energy (E$_{c}$) was determined from the Arrhenius equation based on gel time and curing temperature. As a result, the E$_{c}$ showed a similar behavior with E which could be resulted from high viscosity of PSF and the phase separation between DGEBA and PSF.PSF.f PSF and the phase separation between DGEBA and PSF.PSF.

• Membrane Journal
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• v.6 no.4
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• pp.203-212
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• 1996

The operating parameters influencing on limiting flux was investigated in the ultrafiltration of PVA, and a new model, which is based on the Amiar model using the concept of heat transfer coefficient, was devised to overcome the limitation of gel-layer model. Using polysulfone plate-unit membrane (MWCO=20,000) and hollow-fiber membrane (MWCO= 30,000), ultrafiltration characteristics of PVA was examined with the variation of operating parameters such as cross flow velocity, transmembrane pressure, temperature, and PVA concentration. According to experimental results, the ultrafiltration of PVA through polysulfone membrane is mainly controlled by well-known phenomena of concentration polarization caused by gel-layer formation. On the contrary, in hollow fiber membrane was observed upward limiting flux which can not be explained by gel-layer model. New model was applied to predict the upward limiting flux behavior with partial satisfaction. The application of new model including viscosity correction factor, however, revealed that PVA ultrafiltration is closely related to the viscosity of permeating fluid.

• Journal of the Korean Electrochemical Society
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• v.7 no.2
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• pp.89-93
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• 2004

Sulfonated polysulfone (SPSF) with poly(phenylmethyl silsesquioxane, PPSQ) composite polymer electrolyte membranes were prepared and their proton conductivity, water uptake and methanol permeability of membranes were characterized. By controlling the ratio of $(CH_3)_3SCI\;and\;CISO_3H$ and reaction time, SPSF with $37\~75\%$ degree of sulfonation were synthesized. The increase of sulfonate groups in the base polymer resulted in the increase of the water uptake in the membranes as well as methanol permeability. Composite membranes were prepared by casting of DMF solution of SPSF and PPSQ. The proton conductivity of the composite membrane at room temperature was $2.8\times10^{-3}\~4.9\times10^{-2}S/cm.$ The increase of PPSQ contents in composite membranes resulted in a decrease in water uptake and methanol permeability. Composite membranes containing $5\%$ PPSQ did not make a significant effect on the proton conductivity nO methanol permeability compared with that of pristine SPSF, but a significant decrease of water uptake was observed.

• Korean Membrane Journal
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• v.5 no.1
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• pp.18-24
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• 2003

In order to improve the mechanical properties of the sulfonated polysulfone (SPSf) membranes previously synthesized in our laboratory, poly(vinyl alcohol) (PVA) was blended which is well known as the excellent physical and chemical properties. The resulting membranes blended with several molecular weight of PVA varying from 13,000 to 124,000 have been characterized to investigate the effect of PVA molecular weight in terms of ion conductivities, methanol permeabilities, water contents and ion exchange capacities for both heat treated and untreated membranes at 150$^{\circ}C$. The proton conductivity is decreased as the molecular weight of PVA increases. The plain SPSf-6.0 showed the proton conductivity of 0.078 S/cm whereas the blended membrane with M.W. 31,000 PVA indicated 0.04 S/cm. For methanol permeabilities, when PVA is added to SPAf-6.0, methanol crossover is increased because of the gain of the hydrophilicity from 3.4 to 6.5${\times}$10$\^$-6/ $\textrm{cm}^2$/s. For the annealed blended membranes (with M.W. 31,000 PVA), both the methanol corssover and proton conductivity showed very consistent values, about 2.3${\times}$10$\^$-6/ $\textrm{cm}^2$/s and 0.036 S/cm, respectively.