• Polymer(Korea)
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• v.33 no.4
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• pp.313-318
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• 2009

Copolyimides were synthesized from bis (3-aminophenyl) sulfone (APS) and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) containing a fluorine substituent ($-CF_3$) with different mole ratios of 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA) containing a sulfone group (-$SO_2$-). The PI films were obtained from poly (amic acid) (PAA) by solution casting through thermal imidization on a glass plate. Wide-angle X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), universal tensile machine (UTM) measurements, and UV-Vis spectrometry were used to assess thermo-mechanical properties, morphology, and optical transparency. Thermal properties and optical transparency decreased with increasing DSDA mole fraction. In contrast, mechanical properties increased with increasing DSDA mole fraction. As compared to conventional PI films, however, the PI copolymer films in this work were found to exhibit better optical transparency.

• Membrane Journal
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• v.17 no.2
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• pp.81-92
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• 2007

Membrane-based separation processes are receiving increasing attention in the scientific community and industry since they provide a desirable alternative to processes that are not easy to achieve by conventional separation technologies. In particular, gas separation using polymeric membranes have annually grown so fast owing to advantages such as easy installation, no moving parts, small footprint and low energy process. The key element is definitely a polymer membrane exhibiting high permeability and high selectivity to compete with other gas separation technologies. Current polymer membranes used for commercial gas separation are a family of hydrocarbon polymers for hydrogen separation, air separation and carbon dioxide separation from natural gas sweetening. Relatively, gas or vapor separation properties of fluoropolymers are not known so much as compared with those of hydrocarbon polymers. Accordingly, in this study, membranes prepared from amorphous perfluoropolymers are of particular interest because of the unique properties of these polymers. The advantages offered by these amorphous perfluoropolymers for use in gas and vapor separation will be discussed. In addition, membrane properties and separation performance will be compared with other membranes available on the market.

• Polymer(Korea)
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• v.34 no.1
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• pp.1-7
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• 2010

To enhance the transport properties of gas separation membrane, we prepared 6FDA-6FpDA based polyimide membrane with PMMA-graft-silica nanoparticles. The silica was grafted PMMA which is miscible with 6FDA-based polyimide after surface treatment by 3-methacryloxypropyltrimethoxysilane ($\gamma$-MPS). The untreated silica/6FDA-6FpDA membrane showed greater permeability and less selectivity than PMMA-g-silica/6FDA-6FpDA due to its low dispersion. The transport properties of PMMA-g-silica/6FDA-GFpDA membrane were measured as a function of filler concentration. These membranes were evaluated using pure gases (He, $O_2$, $N_2$, $CO_2$). The increase in permeation was attributed to changes in the free volume distribution until 1 wt%. After 1 wt%, the permeability was decreased by excess silica which decreased effective area in polymer matrix. The selectivity was decreased with increasing permeability on the whole. However, the selectivity of $CO_2$ showed more enhance value.

• Korean Chemical Engineering Research
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• v.48 no.1
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• pp.45-52
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• 2010

Two different imide oligomers(6FDA-ODA/APA and 6FDA-MDA/MA) having crosslinkable end groups were prepared by using a solution imidization method and their properties were investigated. Also, semi-interpenetrating polymer networks(semi-IPN) were prepared using the blends of imide oligomers with polyetherimide $Ultem^{(R)}$, which is used in dual-ovenable packaging materials. The characteristic properties of semi-IPN films were interpreted by using TGA, Thin Film Diffusion Analyzer, and WAXD. Molecular weights of imide oligomers were successfully controlled utilizing 2-aminophenylacetylene(APA) and maleic anhydride(MA) as an endcapping agent. Exotherm reactions by crosslinking appeared and the amount of exthotherm heat was linearly increased as the content of imide oligomers was increased. For semi-IPNs of $Ultem^{(R)}$ and imide oligomers, 5% and 10% weight loss temperatures increased as the contents of imide oligomers were increased. Diffusion coefficient and water uptake of semi-IPNs decreased as the content of imide oligomers was increased, which might be resulted from hydrophobic fluorine group and high packing density. It was concluded that relatively low thermal stability and hydrolytic stability of polyetherimide $Ultem^{(R)}$ were improved by incorporating new developed imide oligomers.

• Membrane Journal
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• v.17 no.4
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• pp.287-293
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• 2007

Pervaporation separation of toluene from water were studied using hydrophobic copolyimide membranes. The copolyimide membranes were prepared from 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and two diamines (polysiloxane diamine (SIDA)/2-(perfluorohexyl) ethyl-3,5-diaminobenzene (PFDAB)). The pervaporation properties for toluene/water were investigated in terms of mol ratio of SIDA/PFDAB in polyimide membranes. Sorption- and diffusion-related properties were measured to analyze the permeation properties in solution-diffusion theory, It was found that as the SIDA content in the membranes increased, sorption of toluene and sorption selectivity of toluene/water increased due to high affinity of siloxane moiety toward toluene. Diffusion coefficient of toluene and diffusion selectivity of toluene/water also increased with SIDA content due to high free volume of siloxane moiety. As the results, the permeation flux and pervaporation selectivity increased markedly from 0.005 $kg/m^2h$ to 049 $kg/m^2h$ and from 9 to 6380, respectively.

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.296-301
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• 2017

Recently, there are many efforts focused on development of more economical non-fluorinated membranes for PEMFCs (Proton Exchange Membrane Fuel Cells). In this study, sulfonated poly (ether ether ketone) (sPEEK) membrane reinforced with poly imide was made to enhance of membrane durability. In order to test durability of single (un-reinforced) membrane and reinforced membrane MEA (Membrane and Electrode Assembly), degradation accelerated stress test was used. Before and after degradation, I-V polarization curve, hydrogen crossover current, electrochemical surface area, membrane resistance and charge transfer resistance were measured. As a result of experiments, hydrogen crossover current of reinforced MEA was lower than that of single MEA, therefor durability of reinforced MEA was higher than that of single MEA. There was not especially short phenomena in reinforced MEA after degradation accelerated stress test.

• Applied Chemistry for Engineering
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• v.30 no.2
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• pp.212-218
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• 2019

To investigate the effect of the oxyfluorination of carbon nanotubes (OF-CNTs) on electroless Ni deposition and electromagnetic interference shielding efficiency (EMI SE), CNTs were treated with a mixture of oxygen and fluorine gases and sequentially deposited with nickel. These samples were then manufactured into thin films on a polyimide film to evaluate their EMI SE. The surface chemical property of OF-CNTs was investigated by X-ray photoelectron spectroscopy. From the results of thermogravimetric and scanning electron microscopic analyses, it was found that both the amount of deposited Ni and the surface morphology changed depending on oxyfluorination. Moreover, the Ni-deposited CNTs pretreated with $O_2:F_2=1:9vol%$ exhibited the maximum EMI SE as approximately 19.4 dB at 1 GHz. These results were attributed to the formation of oxygen and fluorine functional groups on the surface of CNTs due to the oxyfluorination, and the functional groups enabled to deposit a suitable amount of Ni and improve the dispersion in the deposited solution.

• Membrane Journal
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• v.25 no.1
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• pp.60-66
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• 2015

To investigate the performance of the composite carbon electrodes which the ion exchange polymers were directly casted onto porous carbon electrode surfaces, the adsorption/desorption experiments were carried out by varying the feed concentration, feed flow rate, and desorption voltages for the NaCl solution. When the feed concentration was 100 mg/L, the increase of the adsorption time led to the increase of the salt removal due to the increase of the residence time inside the cell while the increase of the feed flow rate from 15 mL/min to 23 mL/min gave the decrease of the salt removal efficiency, 12% because of the short residence time. When the feed concentration was 200 mg/L, the salt removal was shown 10~15% low because of the incomplete desorption within the desorption intervals.