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Gas Transport Properties (gas + transport_property)
Selected AbstractsGas transport properties of asymmetric polyimide membranes prepared by plasma-based ion implantationPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2009Teppei Tezuka Abstract In this study, we report the gas permeance and selectivity of the asymmetric polyimide membrane prepared by plasma-based ion implantation (PBII). The asymmetric polyimide membranes were prepared using a dry,wet phase inversion process, and the surface skin layer on the membrane was implantated by He ions at 2.5,keV. The asymmetric membranes treated by PBII were measured using a high vacuum apparatus with a Baratron absolute pressure gauge at 76,cmHg and 35°C. The (O2/N2) and (CO2/CH4) selectivities in the He+ -implanted asymmetric membrane at 60,sec resulted in 1.5 and 1.8 time increases, respectively, when compared to those of the asymmetric membrane before PBII. On the other hand, the O2 and CO2 permeances in the asymmetric membrane after PBII decreased with an increase in the He+ treatment time. In this paper, we addressed, for the first time, the gas permeation behavior of the asymmetric polyimide membranes prepared by PBII. Copyright © 2009 John Wiley & Sons, Ltd. [source] Effects of membrane thickness and heat treatment on the gas transport properties of membranes based on P84 polyimideJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Yi Shen Abstract P84 polyimide membranes with thicknesses ranging from 6 to 310 ,m were successfully fabricated by spin coating. The glass transition temperature of the P84 powder was found to be 315°C using differential scanning calorimetry, whereas its decomposition temperature was 536°C using thermogravimetric analysis. Scanning electron microscopy was used to examine the morphology of the membranes. The permeability of single gas (He, N2, O2, and CO2) and the ideal selectivity of gas pair (O2/N2, He/CO2, CO2/N2, and He/O2), as a function of membrane thickness, were determined. The results showed that the permeability of a single gas increased with increasing membrane thickness, whereas the selectivity of a given gas pair was nearly independent of the membrane thickness. The average selectivity of O2/N2, He/CO2, CO2/N2, and He/O2 were found to be 8.2, 10.0, 12.9, and 15.8, respectively. The effects of heat treatment on the membrane morphology and gas transport properties were investigated for three annealing temperatures, i.e., 80°C, 200°C, and 315°C. The membrane annealed at 315°C was cracked due to the stress sustained either during heating or cooling, thereby resulting in little or no selectivity. The permeabilities of P84-118 membrane (118 ,m thickness) annealed at 80°C were 16.2, 0.196, 1.20, and 2.01 Barrer for He, N2, O2, and CO2, respectively. The permeabilities of P84-118 membrane annealed at 200°C decreased by 9.75%, 47.96%, 25.83%, and 30.85% for He, N2, O2, and CO2, respectively, as compared with those at 80°C, whereas the ideal selectivities increased by 42.65%, 30.52%, 32.85%, and 21.63% for O2/N2, He/CO2, CO2/N2, and He/O2, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Relationship between gas transport properties and fractional free volume determined from dielectric constant in polyimide films containing the hexafluoroisopropylidene groupJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Sou Miyata Abstract The dielectric constant and gas transport properties (i.e., permeability, diffusivity, and solubility) in 2,2,-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA)-based polyimides were systematically investigated in terms of their polymer fractional free volumes (FFVs) at 30°C. The permeability and diffusion coefficients of the 6FDA-based polyimide films to hydrogen, oxygen, nitrogen, methane, and carbon dioxide were correlated with their FFVs estimated using van Krevelen's group contribution method. There appeared, however, small linear correlation coefficients. Linear correlations were also observed between the gas transport properties and dielectric constant of these polyimides. This study described FFVas a function of the dielectric constant based on the Clausius-Mossotti equation. It was found that the gas permeability and diffusion coefficients of these 6FDA-based polyimide films increased as their dielectric constant-based FFV increased. A better linear relationship was observed between the gas transport properties and the FFV determined from the polymer dielectric constant in comparison to that estimated using the group contribution method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] Impact of H+ ion beam irradiation on Matrimid®.JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Abstract Ion beam irradiation is an easily controlled method to modify the chemical structure and microstructure of polymers including the fractional free volume, free volume distribution and chain mobility, thus altering the gas transport properties of the irradiated polymers. The previous paper focused on the impact of H+ ion beam irradiation on chemical structural evolution of the polyimide Matrimid®. This paper focuses on the impact of H+ ion beam irradiation on microstructure and gas permeation properties of Matrimid®. Irradiation at low ion fluence resulted in slight decreases in permeabilities for five gases (i.e., He, CO2, O2, N2, and CH4) with increases in permselectivities for some gas pairs (e.g., He/CH4 and He/N2). In contrast, irradiation at relatively high ion fluences resulted in simultaneous increases in permeabilities and permselectivities for most gas pairs (e.g., He/CH4, He/N2, O2/N2, and CO2/CH4). While Matrimid® has bulk gas permeation properties that are below the range of commercially interesting polymers, samples irradiated at high ion fluences exhibited significant improvement in gas separation performances. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1670,1680, 2007 [source] | ||||||||||