Showing papers on "Permeation published in 2003"
TL;DR: Carbon molecular sieves (CMSs) have been incorporated into two different polymer matrices to form mixed matrix membrane films for gas separations as mentioned in this paper, which have an intrinsic CO2/CH4 selectivity of 200 with a CO2 permeability of 44 −Barrers and an O2/N2 selectivity with 133 with an O 2 permeability at 35 −C.
679 citations
TL;DR: In contrast to the performance of traditional filled polymer systems, penetrant permeability coefficients in high-free-volume, glassy poly(4-methyl-2-pentyne) (PMP) increase systematically and substantially with increasing concentration of nonporous, nanoscale fumed silica (FS) as discussed by the authors.
Abstract: In contrast to the performance of traditional filled polymer systems, penetrant permeability coefficients in high-free-volume, glassy poly(4-methyl-2-pentyne) (PMP) increase systematically and substantially with increasing concentration of nonporous, nanoscale fumed silica (FS). For instance, the permeability of PMP containing 40 wt % FS to methane is 2.3 times higher than that of the unfilled polymer. Gas and vapor uptake in the PMP/FS nanocomposites is essentially unaffected by the presence of up to 40 wt % FS, while penetrant diffusion coefficients increase regularly with increasing filler content. This increase in diffusivity is responsible for elevated permeability in the PMP/FS nanocomposites. The addition of FS to PMP augments the permeability of large penetrants more than that of small gases, consistent with a reduction in diffusivity selectivity. Consequently, vapor selectivity in the nanocomposites increases with increasing FS concentration. Activation energies of permeation in PMP decrease with...
355 citations
TL;DR: In this article, the authors measured the gas permeability of adhesives of organically modified montmorillonite (OM) and polyurethane (PU) composites to oxygen and water vapor.
Abstract: Adhesive nanocomposites of organically modified montmorillonite (OM) and polyurethane have been synthesized and their permeability to oxygen and water vapor has been measured. The gas permeation through the composites was correlated to the volume fraction of the impermeable inorganic part of the OM. The incorporation of small volume fractions of the platelike nanoparticles in the polymer matrix decreased the gas transmission rate, when the interface between the two heterogeneous phases was properly designed. The oxygen transmission rate decayed asymptotically with increasing aluminosilicate volume fraction and a 30% reduction was achieved at 3 vol %, when the clay was coated with bis(2-hydroxyethyl) hydrogenated tallow ammonium or alkylbenzyldimethylammonium ions. In contrast, coating the clay surface with dimethyl dihydrogenated tallow ammonium ions leads to an increase in the gas transmission rate with augmenting inorganic fraction. This was attributed to a probable change in morphology resulting from phase separation at the interface between the apolar pure hydrocarbon clay coating and the relatively polar PU. The water vapor permeation through the PU nanocomposites was more strongly reduced than oxygen and a 50% reduction was observed at 3 vol % silicate fraction. This was attributed to stronger interactions and hydrogen bonding of the water molecules with the PU matrix as well as to their clustering. Differences in the hydrophobicity of the clay coating influenced the water transmission rate. No spectroscopic evidence could be obtained for a reaction between the hydroxyl groups of the clay organic coating and the isocyanate groups of the prepolymer. A mixed morphology, that is, exfoliated layers and intercalated particles was observed in all composites. WAXRD and TEM gave a qualitative picture of the microstructure of the nanocomposites but no conclusive information. Some of the problems to be solved before a correlation between the nanocomposite properties and their microstructure can be established have been outlined.
293 citations
TL;DR: In this article, fundamentally-based analytical expressions that can be used to predict skin permeability to hydrophilic as well as hydrophobic solutes were compiled. But none of these expressions can be applied to human skin.
283 citations
TL;DR: In this article, the authors investigated the permeability of formic acid through Nafion® membranes at room temperature and found that the permeation rate was much slower than methanol through the same membrane.
268 citations
TL;DR: The influence of ionic strength (I) and pH on the permeability of polyelectrolyte multilayers (PEMs) was studied in this paper, where fluorescein crystals were coated with a poly(styrenesulfonate) (PSS)/poly(allylamine hydrochloride) (PAH) multilayer shell at pH 2.0 and subsequently dissolved at pH 7.0 or 8.0.
Abstract: The influence of ionic strength (I) and pH on the permeability of polyelectrolyte multilayers (PEMs) was studied. Fluorescein crystals were coated with a sodium poly(styrenesulfonate) (PSS)/poly(allylamine hydrochloride) (PAH) multilayer shell at pH 2.0 and subsequently dissolved at pH 7.0 or 8.0. From the release profiles, permeability coefficients for fluorescein diffusion through PEMs were found to depend on pH and I. Permeability coefficients changed from 1.0 × 10-7 to 6.6 × 10-8 m/s at pH 7.0 and from 4.5 × 10-8 to 8.7 × 10-9 m/s at pH 8.0, while the salt concentration was varied from 500 to 10 mM. Decrease of the permeability coefficients while going from pH 7.0 to pH 8.0 occurred due to the increase of the repulsion between the fluorescein molecule and the PEM. The found dependencies indicated that permeation occurs through the water-filled cavities in the multilayers. The permeability is suggested to be dependent on the free energy of the interpolyelectrolyte interaction and to be the function of ...
234 citations
TL;DR: In this paper, a concept for measuring ultralow permeation rates was demonstrated for polyester foils with single-and double-sided barrier coatings, and the resulting base line contribution to the water vapor transmission rate of a glass reference was below 10−6 ǫg/m2
Abstract: Highly sensitive permeation measurements are crucial for the characterization and development of polymeric substrates for flexible display applications. In particular, organic light-emitting devices require substrates with extremely low permeation rates for water and oxygen. Here we demonstrate a concept for measuring ultralow permeation rates. The amount of oxidative degradation in a thin Ca sensor is monitored by in situ resistance measurements. The benefits of this technique are demonstrated for polyester foils with single- and double-sided barrier coatings. A sensitivity limit is imposed by the quality of the encapsulation. The resulting base line contribution to the water vapor transmission rate of a glass reference is below 10−6 g/m2 day at accelerated test conditions.
231 citations
TL;DR: In this paper, the authors present an experimental study on permeation properties of a range of different self-compacting concrete (SCC) mixes in comparison with those of selected traditional vibrated reference (this paper) concretes of the same strength grade.
205 citations
TL;DR: In this paper, surface modified polyethersulfone ultrafiltration membranes (MWCO: 9000, 35,000 and 85,000) were surface modified by preadsorption of poly(sodium 4-styrenesulfonate) (PSS) upon the permeation of aqueous solution of the polymer for about 100min.
203 citations
TL;DR: In this article, the authors explored the gas separation performance of a modified Matrimid/C60 mixed matrix membranes and found that the decrease of the gas permeability with increasing C60 compositions was mainly due to the decrease in the gas diffusivity.
197 citations
TL;DR: In this paper, a generalized cross-linking strategy is presented that enables analysis of the effects of the cross-link agent structure and thermal treatment on pure gas permeation and sorption for CO2 and CH4 at 35 °C.
Abstract: Solid-state covalent cross-linking of 6FDA-based polyimides with esterification reactions is shown to be effective in stabilizing membranes against CO2 plasticization up to 40 atm feed pressure. The selection of cross-linking agent has a major impact on the cross-linking degree and the gas transport properties. A generalized cross-linking strategy is presented that enables analysis of the effects of the cross-linking agent structure and thermal treatment on pure gas permeation and sorption for CO2 and CH4 at 35 °C. The polyimide 6FDA-DAM:DABA 2:1 was cross-linked with ethylene glycol, 1,4-butylene glycol, 1,4-cyclohexanedimethanol, and 1,4-benzenedimethanol to illustrate these effects. The cross-linking degree is evaluated by a combination of solution 1H NMR and solid-state IR spectroscopy. The annealing temperature is a significant factor in determining the membrane transport properties, since it affects the polymer chain rigidity and free volume distribution. It is believed that this cross-linking appro...
TL;DR: In this paper, an organic binder solution (dope) containing suspended aluminium oxide (Al 2 O 3 ) powders, either in mono size or a distributed size, is spun to a hollow fibre precursor, which is then sintered at elevated temperatures.
TL;DR: In this article, the authors used a phenomenological model of membrane transport to measure transport of water and hydrophilic neutral organic solutes spanning a range of molecular sizes across two commercial thin-film composite nanofiltration (NF) membranes in the temperature range 5-41°C.
TL;DR: In this paper, a poly(vinylsulfonic acid/acrylic acid) crosslinked gel in a porous polytetrafluoroethylene (PTFE) substrate was developed for use as electrolyte membranes in a direct methanol fuel cell.
TL;DR: The results emphasize, therefore, that the new transdermal technology is suitable for therapeutic delivery of poorly penetrating molecules.
TL;DR: In this article, the authors studied the effect of physical treatments such as sub-Tg annealing, thermal quenching, and CO2 pressure conditioning on gas sorption and permeation of physically treated glassy polymeric membranes.
TL;DR: Here substrate permeation through the membrane and subsequent chemical transformation at the membrane surface are realized and these methods are expected to lead to development of complicated and sophisticated chemical systems involving membrane permeation and chemical reactions.
Abstract: Here we report a design and synthesis of a chemically functional polymer membrane by an interfacial polycondensation reaction and multilayer flow inside a microchannel. Single and parallel dual-membrane structures are successfully prepared by using organic/aqueous two-layer flow and organic/aqueous/organic three-layer flow inside the microchannel followed by an interfacial polycondensation reaction. By using the inner-channel membrane, permeation of ammonia species through the inner-channel membrane is successfully achieved. Furthermore, horseradish peroxidase is immobilized on one side of the membrane surface to integrate the chemical transform function onto the inner-channel membrane. Here substrate permeation through the membrane and subsequent chemical transformation at the membrane surface are realized. The polymer membrane prepared inside the microchannel has an important role in ensuring stable contact of different phases such as gas/liquid or liquid/liquid and the permeation of chemical species th...
TL;DR: In this paper, a laboratory-scale clarified apple juice was clarified in a laboratory scale ultrafiltration system using ceramic tubular membranes (Tech-Sep Carbosep) with a molecular weight cut-off of 300,000, 50,000 and 30,000 Da.
TL;DR: In this paper, a thin MFI zeolite membrane was synthesized on a porous α-Al 2 O 3 tubular support by in situ nucleation and secondary growth, which combines high permeances (1.6-8.0μmolm −2 ǫs −1 Ã −1 ) and also good separation properties (the H 2 /SF 6 permselectivity value is equal to 24 at room temperature).
TL;DR: In this paper, a molecular sieve silica (MSS) membrane packed bed reactor (PBR) using a Cu/ZnO/Al2O3 catalyst was applied to the low-temperature water gas shift reaction (WGS).
TL;DR: In this paper, two types of mesoporous silica membranes have been prepared and characterized, and a membrane fabricated via sol dip-coating was deposited on the polished surface of an alumina support disk.
TL;DR: The study showed that the dermis may be a much more lipophilic environment than originally believed and that distribution of smaller nonionized solutes into local tissues below a site of topical application may be estimated based on knowledge of their lipophilicity alone.
TL;DR: In this paper, the oxide powders were synthesized by solid-state reaction, modified citrate and citrate-EDTA complexing method and showed different grain morphologies.
TL;DR: Asymmetric charged porous membranes were prepared by imbedding 10% ion-exchange resin in cellulose acetate binder and were found to be reasonably homogeneous, employing an interpretation by nonequilibrium thermodynamic principles based on frictional forces.
TL;DR: A solution technique was employed to prepare ZSM-5 zeolite incorporated polyvinyl alcohol (PVA) membranes for the pervaporation separation of water-isopropanol mixtures.
Abstract: A solution technique was employed to prepare ZSM-5 zeolite incorporated poly(vinyl alcohol) (PVA) membranes for the pervaporation separation of water-isopropanol mixtures. The membranes were characterized by Fourier transform infrared spectroscopy and differential scanning calorimeter. Glass transition temperatures of the membranes varied from 102 to 110°C, with increasing zeolite content of the membrane. The effect of zeolite loading and feed composition on pervaporation performance of the membranes was analyzed. The membrane containing 6 mass% of zeolite gave the highest separation selectivity of 216 for 10 mass % of water containing feed mixture at 30°C. Increase in water selectivity of the membrane was explained as due to a reduction in free volume by increasing zeolite content of
the membrane. Separation selectivity and permeation flux data are dependent on water composition of the feed mixture,
but are comparatively less dependent on temperature. The hindrance of water permeation at higher composition of water in the feed mixture was explained as due to the formation of clusters of water molecules. The overall activation energy and preexponential factors were calculated using Arrhenius equation. Pervaporation data have also been explained on the basis of thermodynamic parameters calculated by using Arrhenius equation as well as relationship proposed by Ping et al.
TL;DR: In this paper, the morphology and structure of PAN/PVDF membranes were examined using scanning electron microscope (SEM), and the contact angle, equilibrium water content (EWC), porosity, and mechanical properties were also determined.
TL;DR: The study is focused on the transport of symmetrical electrolytes (with symmetric or asymmetric diffusion coefficients) and the influence of effective membrane charge density, permeate volume flux, pore radius and effective membrane thickness to porosity ratio on the contribution of the different transport mechanisms is investigated.
TL;DR: In this paper, the preparation, the characterization, and the permeation properties of dense flat sheet and asymmetric hollow fiber membranes, based on BTDA-TDI/MDI co-polyimide (P84), are reported.
TL;DR: In this article, an asymmetric tubular alumina-supported poly(vinyl acetate) (PVAc) and poly (vinyl pyrrolidone)(PVP) membranes were created and characterized by pervaporation separation of binary mixtures of methanol and methyl tert-butyl ether (MTBE).
TL;DR: Sulfonated polyimides (SPIs) were prepared from 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTDA), and their water vapor sorption, diffusion and permeation properties were investigated in comparison with Nafion 117 as discussed by the authors.