Gas Permeability Values Research Articles

Effect of ionizing radiation on physicochemical and mechanical properties of commercial multilayer coextruded flexible plastics packaging materials

The effect of gamma radiation (doses: 5, 10 and 30 kGy) on mechanical properties, gas and water vapour permeability and overall migration values into distilled water, 3% aqueous acetic acid and iso-octane was studied for a series of commercial multilayer flexible packaging materials based on coextruded polypropylene (PP), ethylene vinyl alcohol (EVOH), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polyamide (PA) and Ionomer. The results showed that radiation doses of 5 and 10 kGy induced no statistically significant differences ( p>0.05) in all polymer properties examined. A dose of 30 kGy induced differences ( p<0.05) in the mechanical properties of PA/LDPE, LDPE/EVOH/LDPE and LDPE/PA/Ionomer films. In addition, the same dose induced differences ( p<0.05) in the overall migration from Ionomer/EVOH/LDPE and LDPE/PA/Ionomer films into 3% acetic acid and iso-octane and in the overall migration from PP/EVOH/LDPE-LLDPE into iso-octane. Differences recorded, are discussed in relation to food irradiation applications of respective packaging materials.

Electrode permeability and flow-field configuration: influence on the performance of a PEMFC

The objective of this work was to investigate the effect of both the permeability of the electrodes and the configuration of the gas flow distributor on the performance of a proton exchange membrane fuel cell (PEMFC). For that purpose, MEAs including electrodes of two types, carbon paper and carbon cloth, have been characterised electrochemically by measuring the polarization curves for a wide range of operational conditions with H 2 and O 2/air as reactants. MEAs with surface active areas of 50 and 290 cm 2 have been characterised in single cells with two flow-field configurations: a grooved plate with parallel gas channels and solid ribs, and a solid plate. The latter is a novel gas flow distributor that has been designed and tested in our laboratory. A subsequent series of experiments were carried out in order to measure the gas permeability of the electrodes of the MEAs characterised previously. The permeability of the electrodes was measured separately for O 2, N 2 and H 2 in the absence of water vapour. The fuel cell performance strongly depends on both the gas permeability of the electrodes and the type of gas flow distributor. The effect of the electrode permeability is not meaningful in the case of the grooved plates, but it is rather important in the case of the solid plates. With the grooved plates, the differences in the fuel cell performance observed with the various MEAs must be attributed to factors mostly related to the catalyst layer (platinum and Nafion content, dispersion of the catalyst, etc.). With solid plates, however, the MEAs of both short and large sizes performed consistently with the gas permeability values of the electrodes measured in this work. In general, the performance of the fuel cell with solid plates declines when the permeability of the electrodes decreases. In the range of current densities covered here, below 300 mA/cm 2, the MEAs with the more permeable electrodes performed comparably with either grooved or solid plates. The less permeable electrodes were the ones in the MEAs provided by E-TEK, which are made of carbon cloth with 40 wt.% of hydrophobic material. In this case, noticeably higher gas transport losses were observed with the solid plates than with the grooved plates, particularly when air was used as oxidant. The influence of water vapour on the gas electrode permeability and the effect of the electrode hydraulic permeability on the fuel cell performance will be investigated in a future work.

Gas permeability and n‐butane solubility of poly(1‐trimethylgermyl‐1‐propyne)

AbstractThe gas permeability and n‐butane solubility in glassy poly(1‐trimethylgermyl‐1‐propyne) (PTMGP) are reported. As synthesized, the PTMGP product contains two fractions: (1) one that is insoluble in toluene and soluble only in carbon disulfide (the toluene‐insoluble polymer) and (2) one that is soluble in both toluene and carbon disulfide (the toluene‐soluble polymer). In as‐cast films, the gas permeability and n‐butane solubility are higher in films prepared from the toluene‐soluble polymer (particularly in those films cast from toluene) than in films prepared from the toluene‐insoluble polymer and increase to a maximum in both fractions after methanol conditioning. For example, in as‐cast films prepared from carbon disulfide, the oxygen permeability at 35 °C is 330 × 10−10 cm3 (STP) cm/(cm2 s cmHg) for the toluene‐soluble polymer and 73 × 10−10 cm3 (STP) cm/(cm2 s cmHg) for the toluene‐insoluble polymer. After these films are conditioned in methanol, the oxygen permeability increases to 5200 × 10−10 cm3 (STP) cm/(cm2 s cmHg) for the toluene‐soluble polymer and 6200 × 10−10 cm3 (STP) cm/(cm2 s cmHg) for the toluene‐insoluble polymer. The rankings of the fractional free volume and nonequilibrium excess free volume in the various PTMGP films are consistent with the measured gas permeability and n‐butane solubility values. Methanol conditioning increases gas permeability and n‐butane solubility of as‐cast PTMGP films, regardless of the polymer fraction type and casting solvent used, and minimizes the permeability and solubility differences between the various films (i.e., the permeability and solubility values of all conditioned PTMGP films are similar). © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2228–2236, 2002

Experimental study of gas and liquid permeability of a mortar

Eight samples cored from the same mortar were used to investigate their respective gas, ethanol and water permeability. Two gas and liquid permeability cells, using special devices for measuring the injected flow under steady conditions, were designed and presented in this paper. The obtained results showed that water permeability was systematically lower (in an order of magnitude from 1 to 2) than gas permeability whereas ethanol permeability was intermediate between these two values. Nevertheless, ethanol and gas permeabilities were found of the same order and, when gas permeability is corrected from the Klinkenberg (or slippage) effect, the results given by these two fluids are virtually identical and can be considered to be the intrinsic permeability value. Thus, the differences observed between water and gas permeability values have to be explained by other phenomena such as rehydration, dissolution and migration of fine elements or water adsorption in the thinnest pores.

Gas permeability of expanded graphite–metallic salt composite

The expanded graphite–metallic salt composite was manufactured by impregnation of metallic salt solution into porous graphite matrix, followed by vacuum drying. The gas permeability was measured by using Darcy’s law in ammonia atmosphere for the graphite–CaCl 2· nNH 3 ( n=8, 4, 2), MnCl 2· nNH 3 ( n=6, 2) and BaCl 2· nNH 3 ( n=8, 0) composites. The gas permeability was in the range of 5.0×10 −16–10 −12 m 2 depending on the reaction pair, bulk density and weight fraction of the graphite powder. Results show that as the value of n increases, the gas permeability diminishes remarkably due to a reduction of the total porosity. The values of gas permeability obtained in this work are useful in the mass transfer analysis and dynamic simulation of thermochemical reactors for chemical heat pumps.

The importance of gas permeability in addition to the compressive strength of concrete

The permeability to gases of cementitious materials is one of the major contenders for becoming a standard parameter for the quantification of the durability of these materials. This coefficient is thought to be closely related to the compressive strength. It is shown systematically here, by conducting permeability studies as a function of the degree of saturation of concrete on two sets of concrete compositions having the same compressive strength (100 MPa and 25 MPa), that entirely different gas permeability values may exist for different mix compositions which have the same compressive strength. These measurements were carried out on 5 cm thick, 15 cm dia. specimens by using a CEMBUREAU permeameter and oxygen as the percolating fluid. The results emphasize the fact that the 28 day compressive strength alone cannot be a criterion of the durability of concrete unless it is coupled with the quantification of the resistance to the entrance of aggressive chemicals.

Oxygen Gas Permeability of Poly (Aminophosphazene) Films in Water

Various gas permeability in dry and oxygen gas permeability in wet conditions with poly(organophosphazene) membranes have been previously reported [1–2]. To prepare the transparent poly(aminophosphazene) having the highest oxygen gas permeability value (D) in water, chlorine atoms in polydichlorophosphazne (1) were substituted with amine compounds (2).

Gas permeability coefficient of cover concrete as a performance control

A simple and practical gas permeability measurement method, known as the overpressure method, was used to assess the quality of cover concrete. This method enables distinguishing the quality of cover concrete both qualitatively and quantitatively, under laboratory conditions and/orin situ. The gas permeability values obtained are sensitive to changes in curing duration, water/cement ratio, age of testing and moisture history of the concrete. It has been confirmed from the test results that compressive strength alone cannot be a good indicator of concrete durability. It has also been observed that sorptivity and gas permeability values are linearly proportional to each other.

Effect of Basic Substituents on Gas Sorption and Permeation in Polysulfone

The gas permeability, diffusivity, and solubility of a series of polysulfones bearing basic aryl substituents were determined at 35 °C and pressures up to 20 atm. Gas permeability and diffusivity values of the aryl-substituted polysulfones were markedly lower than those of unmodified polysulfone. These effects were ascribed to decreased fractional free volume and increased restriction to sub-Tg torsional motion in the substituted polymers. Polysulfone bearing benzylic amine substituents exhibited higher CO2 solubility and CO2/CH4 solubility selectivity than polysulfone, presumably due to favorable interactions between acidic CO2 molecules and basic −CH2-NH2 groups. CO2 diffusivity in polysulfone bearing benzylic amine substituents is lower than expected based on free volume considerations, suggesting that interactions between CO2 and benzylic amine moieties may be strong enough to impede CO2 mobility in the modified polymer. These results are consistent with infrared spectroscopy data which suggest that t...

Oxygen gas permeability in water and mechanical properties of poly(n-butylamino)-(di-allylamino) phosphazene membranes cured with the irradiation

Poly(n-butylamino) (di-allylamino)phosphazenes were prepared by the reaction of (NPCl2) n withn-butylamine and di-allylamine. After the membranes were prepared by the casting method, they were irradiated by ultraviolet electron beam,60Co γ-rays. It was found from Fourier transform-infrared data that the CH=CH2/N-H ratios of the irradiated membranes decreased with increasing dose. Also, the membrane did not dissolve in tetrahydrofuran or other organic solvents. This supported the idea that the CH=CH2 bond was cleaved by the irradiation and the cross-linking occurred intermolecularly. Oxygen gas permeability values,Dk, of the irradiated membrane were determined from oxygen permeability and mechanical properties were determined with a Tensilon instrument.Dk values decreased with increasing Young's modulus in the case of low concentrations of di-allylamine.

Oxygen gas permeability in water and the properties of poly(organophosphazene) films

[NP(NR2)(NHR)]n and [NP(NR2) (NHR)1−x (OCH2CH2COOCH = CH2)x]n type polymers were prepared by the reaction of (NPCl2)n with various secondary or primary amines and 2-hydroxyethylacrylate. Membranes were prepared by casting, the mixing mill technique and ultraviolet radiation. The oxygen gas permeability of the membranes and the mechanical properties of the membranes were determined using a film oxygen gas permeater and an Instron tester. It was found that [NP(Di-n-hexylamine) (n-butylamine)]n had the highest oxygen gas permeability value; Dk = 116×10−11 cm3 ml cm−2s−1 mm Hg−1. Also, it was found that the oxygen gas permeability of poly (aminophosphazenes) was not directly related to the dielectric constant and mechanical properties of the membranes in wet conditions (water).

Gas transport properties of polysulphones: 3. Comparison of tetramethyl-substituted bisphenols

Abstract The gas sorption and transport properties of a series of polysulphones with tetramethyl ring substitution are reported. The results for tetramethylhexafluorobisphenol A polysulphone (TMHFPSF) and tetramethylbisphenol F polysulphone (TMPSF-F) are compared to tetramethylbisphenol A polysulphone (TMPSF) and bisphenol A polysulphone (PSF). The effect of the substituents on chain mobility and chain packing has been related to the gas transport properties. Dynamic mechanical thermal analysis and differential scanning calorimetry were used to judge chain mobility, while X-ray diffraction and free-volume calculations give information about chain packing. Permeability measurements were made for He, H2, O2, N2, CH4 and CO2 at 35°C over a range of pressures up to 20 atm. Sorption experiments were also done for N2, CH4 and CO2 under the same conditions. The permeability coefficients of the methyl-substituted polymers rank in the order TMHFPSF ⪢ TMPSF > TMPSF-F for all of the gases. This is the same order as the unsubstituted materials, hexafluorobisphenol A polysulphone (HFPSF), PSF and bisphenol F polysulphone (PSF-F), which suggests that the effects of tetramethyl substitution are somewhat additive with other structural modifications. Relative gas permeability values are in agreement with relative fractional free-volume values as well as with γ transition temperatures.

Gas separation membranes: A novel application for conducting polymers

Gas permeability values are reported for films of the conducting polymer polyaniline in the emeraldine oxidation state. Substantial improvements in gas selectivity, when compared to literature values, were observed for all gas pairs studied (He/N 2, H 2/N 2, O 2/N 2, CO 2/CH 4). The doping procedure which enables conductivity in the film was found to cause significant concurrent changes in the film morphology which resulted in improved gas separations. These morphological changes primarily influence the permeant diffusivity as shown by comparison to the kinetic diameter of the permeant. The potential for development of conducting polymer membranes with precisely controlled morphology is clearly indicated, allowing optimization of films for any gas separation.

Geological Controls on Natural Gas Production in the Antrim Shale of the Michigan Basin: ABSTRACT

The Antrim Shale (Devonian-Mississippian) is a prolific natural gas reservoir with distinctive source rock and reservoir characteristics. The Antrim is composed of two distinctive lithofacies: a black shale lithofacies having total organic carbon (TOC) values as high as 12% and a gray-green shale lithofacies having TOC values generally below 0.5 %. The black shale facies is the primary source bed and reservoir for natural gas. Based on Rock-Eval data the kerogen in the Antrim Shale is only marginally mature with respect to generation of liquid hydrocarbons. This in the range of 435{degree}C, vitrinite reflectance values are 0.41, and thermal alteration index (TAI) is 2. These data indicate a maximum burial temperature of approximately 60{degree}C in Otsego County, Michigan, the main play area. Although the thermal maturation level in this area is very low, the gas produced from the Antrim is internally sourced and thermogenic; this interpretation is based on the presence of trace amounts of high-gravity oil and a thermogenic isotopic signature of produced gas samples. The black shale facies in the Antrim contains significant authigenic silica and is more susceptible to fracturing compared to the carbonate-cemented gray-green shales facies. Extremely low gas permeability values (0.1 md) indicates that fracturesmore » serve as conduits for delivery of gas to the borehole. Most of the gas must be stored in the shale matrix porosity because total gas volume produced far exceeds fracture reservoir volume.« less

Oxygen gas permeability of poly(organophosphazene) membranes in water

Fifteen different poly(organophosphazenes) were synthesized by the reaction of poly(dichlorophosphazene) (NPCl 2) n with phenoxide, alkoxide and amine compounds. Membranes were prepared from the synthesized poly(organophosphazenes) by a casting method, and the oxygen gas permeability of the membranes was determined using a film oxygen gas permeater at 20°C in water. It was found that poly(diethylaminobutyl-aminophosphazene) had the highest oxygen gas permeability value, Dk=55.2 × 10 −11cm 2s −1mmHg −1. The glass transition temperatures and dielectric constants of the polymers were determined with an inductive-ratio-arm bridge to determine their effect on oxygen gas permeability. It was found that the oxygen gas permeability of poly(aminophosphazenes) was most directly related to the dielectric constant in the case of wet conditions (water).

粒状試料による石炭のガス透過率測定

Methane in a coal seam flows into a gas drainage bore hole through a two-step process; firstly diffusion through solid coal and secondly flow along interconnected fissures.The purpose of this paper is to estimate the gas permeability of solid coal which contains few or no fissures in it. This permeability is thought to be useful for understanding gas flow characteristics of gas drainage bore holes in a virgin solid coal seam. The apparatus used in this experiment is shown in Fig. 1. As the smaller the coal particle, the fewer the fissures in it, powdered coal samples ranging from 20mesh to 100mesh were used for this experiment. Basing upon Darcy's law, the equations describing gas emission from powdered coal and change of gas pressure in the flask were derived. Comparing the calculated gas pressure change with the measured ones, gas permeabilities of two coal seams were estimated as approximately 10-10 darcy. Owing to the low gas permeability of solid coal, gas drainage from coal seam is thought to be difficult if the coal seam does not contain any fissures. In addition to this, experimental values of gas permeability agree well with the easinesses of gas drainage from in-situ coal seams.