The barrier properties of polyethylene terephthalate to mixtures of oxygen, carbon dioxide and nitrogen

The diffusion and solubility of oxygen, nitrogen and carbon dioxide have been studied in amorphous and biaxially oriented films of polyethylene terephthalate (PET). To measure the sorption and desorption of each gas simultaneously in cases where mixtures of gases were studied, a mass spectrometer was used as a detector. It was found that the solubility and diffusion of nitrogen in PET were markedly affected by the presence of the other gases, oxygen and carbon dioxide with differences in detail between results for the amorphous and biaxially oriented films. It is of particular interest that the presence of oxygen reduces the solubility and increases the diffusivity of nitrogen.     

Effect of annealing on the permeation characteristics of gases of coextruded LLDPE films

The temperature dependence of both the permeability and diffusion coefficients of carbon dioxide, oxygen and nitrogen in annealed LLDPE films are studied. It is found that the values of the permeability coefficient through the annealed membranes are nearly four times larger than those through the non-annealed ones. The fact that annealing slightly diminishes the values of the diffusion coefficient leads to the conclusion that the rise in permeability detected in the films by effect of annealing should be attributed to an increase in solubility. The permeability characteristics of the films are interpreted in terms of the free volume theory.     

Diffusional characteristics of coextruded linear low-density polyethylenes prepared from different conditions of processing

The permeability and diffusivity of oxygen, carbon dioxide, nitrogen, and helium have been obtained for a range of linear low density polyethylene (LLDPE) films prepared from the same raw materials but with different processing conditions. The measurements were carried out by means of a permeation technique over the temperature interval where the α-relaxation processes were observed in earlier studies. The temperature dependence of the permeability and diffusion coefficients of gases shows 2 well-differentiated regions in all films. The break temperature of these regions is approximately located at the same temperature as the α-relaxation takes place. Both the permeability and their temperature dependence do not show a noticeable influence on the processing conditions. The effect of processing conditions on the diffusivity seems to be more complex. Differences are observed for different films in the diffusion coefficients, in the case of oxygen, and in their change with the temperature, which is particularly marked in the case of carbon dioxide. Fujita's free volume model has been applied to diffusivity data in order to study the influence of films microstructure in gas permeation properties through them. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 23–37, 1998     

The electrochemistry of gases at metallized membrane electrodes

The electrochemistry of four gases, hydrogen, nitric oxide, nitrogen dioxide and sulphur dioxide at metallized membrane electrodes is reported. It is shown that, as was the case with oxygen and carbon monoxide, it is possible by suitable choice of electrode potential, electrode metal and electrolyte to find conditions where the currents are determined by the rate of diffusion of the electroactive species through the membrane. The experimental data are used to estimate values for the diffusion coefficient and solubility of the gases in the membrane material and the relevance to the design of environmental monitors of these experiments with high partial pressures of gases is discussed.     

Gas transport and thermal characterization of mono‐ and di‐polyethylene films used for food packaging

The permeability of carbon dioxide, oxygen, nitrogen, and air through commercial monolayer and multilayer films, based on polyethylene (PE), biaxially oriented polypropylene (BOPP), and polyamide (PA), used for food packaging is reported. The influence of temperature (from 10 to 60°C) on permeability and DSC characteristics changes was also analyzed. Literature data for gas permeability of the mentioned monofilms are quite variable due to differences in additives, thermal history, and crystallinity. In this work, the highest gas permeability is obtained for PE film at the higher temperature (50–60°C). Laminates exhibit different gas permeation behavior from that of monofilms. Generally, gas solubility coefficient increases at higher temperature (with an exception of PA/PE and BOPPcoex.met/PE), being higher for monofilms in comparison with laminates, while diffusion coefficients are lower for monofilms in comparison with laminates. The temperature dependence of the permeability, diffusivity, and solubility of gases shows two different regions in PE, BOPPcoex/PE (10–40°C and 40–60°C), PA/PE, and BOPPcoex.met (10–30°C and 40–60°C) films. Correlation between activation energies for permeation and diffusion as well as heat of sorption and 17 gas properties is performed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1590–1599, 2006     

Direct measurement of gas solubilities in polymers with a high‐pressure microbalance

Solubility and diffusion data are presented for methane and carbon dioxide gases in high‐density polyethylene. The polymer was cut from extruded piping intended for use in offshore oil and gas applications. The measurements were carried out with a high‐pressure microbalance. The properties were determined from 25 to 50°C and from 50 to 150 bar for methane and from 20 to 40 bar for carbon dioxide. In general, a good agreement was obtained with similar measurements reported in the literature. The solubility followed Henry's law (linear) dependence with pressure, except at high pressures for methane, for which negative deviations from Henry's law behavior were observed. The diffusion coefficients for each of the gases in the polymer were also measured with the balance, although the uncertainty was greater than for the solubility measurements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1476–1488, 2004     

Equilibrium and Transport Properties of Gases in E-Glass Melts

The solubility and diffusion coefficients of oxygen, sulfur dioxide, and water were determined (and those for nitrogen, carbon dioxide, and argon were estimated) in commercial E-glass melts as a function of melt temperature and atmosphere. Knowledge of these fundamental constants of gases in glass melts is required for the development of models for bubble growth and elimination within the melt. The effectiveness of fining agents can be traced to the production of those gases in the melt which possess the greatest variation in solubility and diffusion as a function of the temperature and atmosphere. Accordingly, oxygen through multivalent elements and sulfur are the best fining agents for glass production.     

Permeation of gases through modified polymer films. I. Polyethylene–styrene graft copolymers

The permeabilities of nitrogen, oxygen, and carbon dioxide through polyethylene–styrene graft copolymer films were measured by means of a gas permeability apparatus based on a modification of Barrer's high vacuum technique. Polyethylene–styrene grafts were prepared by mutual γ-ray irradiation of low-density polyethylene films in styrene–methanol solution. Densities and thicknesses of the graft copolymer films were determined. It was observed that the gas permeability constants decreased with increasing grafting to minimum values at 20–30% styrene grafting and increased again above 30% grafting. These results are explained in terms of a decrease in the free volume of the amorphous regions of the polyethylene by a “filling in” effect of the grafted polystyrene chains. Above 30% grafting, disruption of the crystallites may occur resulting in increased gas permeation. Activation energies for gas permeation through polyethylene–styrene graft copolymer films were calculated and found to decrease with increasing per cent styrene grafting. For nitrogen permeation, the activation energy decreased from 11.7 kcal/mole for unirradiated polyethylene to 9.5 kcal/mole for a 50.5% graft. Corresponding values for oxygen and carbon dioxide were 10.2–8.2 kcal/mole for a 48.7% graft and 8.4–6.5 kcal/mole for a 50.5% graft.     

CO等气体在苯酚中的溶解度的测定及关联

建立了一套用于测定高中压下气体在黏度大、易结晶高黏度溶剂中溶解度的汽液平衡测定装置,该装置采用整体温浴、流动的方法很好地解决了溶剂苯酚易结晶而带来操作困难的问题,利用该套高中压汽液平衡测定装置,在不同温度和压力下,测定了CO₂、CO、N₂、O₂气体在纯苯酚中的溶解度数据.采用RK方程的维里展开式和正规溶液理论推算得到的气体溶解度与温度和压力的函数关系式,并对相同温度和压力下CO等气体在纯苯酚中的溶解度进行了三参数关联,得出了溶解度的计算模型.最后,用这一模型关联计算CO₂、N₂、O₂和CO在纯苯酚中的溶解度,结果表明,计算值和实验值误差较小,因此,该计算模型可以用于对相同温度下加压气体在纯苯酚中溶解度的关联和内插计算.     

Gas transport in ethylene-propylene-diene (EPDM) elastomer: Molecular simulation and experimental study

Time lag permeation measurements with ethylene-propylene-diene (EPDM) elastomer have been undertaken in an effort to characterize the gas transport properties of this barrier material. The derived solubility and diffusivity of a series of probe gases including helium, hydrogen, neon, argon, krypton, oxygen, nitrogen, carbon dioxide and methane were measured and compared with molecular simulation predictions. Molecular Dynamics (MD) and Grand Canonical Monte Carlo (GCMC) calculations were performed to provide estimates for diffusivity and solubility, respectively. Agreement between the molecular simulations and experimental data is obtained for simple spherical monatomic probe gases, with greater deviation observed for non-spherical polyatomic gases. Additionally, agreement between semi-empirical correlations based on the effective cross-sectional area of the diffusing species and the effective Lennard-Jones interaction constant of the sorbed species is better than widely used correlations based on gas critical properties. Furthermore, the molecular simulations provide a meaningful representation for the elastomer studied and additionally appear to capture the fundamental principles of sorption and diffusion of the chosen probe gases.     

The permeation of gases through modified polymer films. II. Gas permeability and separation characteristics of gamma ray-irradiated polyethylene

A study has been made of the diffusion, solubility, and separation of nitrogen and methane gases in a series of air-and vacuum-irradiated polyethylene films in the temperature range of 15° to 50°C. Samples were air irradiated to 90 Mrads and vacuum irradiated to 80 Mrads. The major structural differences between the modified films were the presence of oxygenated species in the air-irradiated samples. The oxidation of these samples reduced the amount of crosslinking normally found in vacuum-irradiated samples. Diffusion and permeability coefficients for both gases decreased with irradiation dose. The solubility coefficients for the air-irradiated samples increased with increasing irradiation dose while little change was observed for vacuum-irradiated film. The gas mixture permeabilities could be predicted from the pure component permeabilities, and the methane–nitrogen separation factor decreased with increasing irradiation dose.     

The permeation of gases through modified polymer films. IV. Gas permeability and separation characteristics of graft copolymers of polyethylene and teflon FEP films

The effects of grafting styrene and acrylonitrile onto polyethylene and Teflon FEP films on their gas permeation and separation properties were investigated. The time-lag method was used to determine the permeability, diffusion, and solubility coefficients of nitrogen and methane gases in the grafted films. The separation factors of nitrogen—methane gas mixtures were measured by gas chromatography. Structural and morphologic changes in the modified films were examined by density, differential scanning calorimetry, and infrared measurements. Attempts were made to relate these changes to the gas permeation and separation characteristics of the films. Modification by graft copolymerization resulted in slightly improved separation factors; however, the permeability and diffusion coefficients decreased. The experimental permeability and diffusion coefficients for gas mixtures were in good agreement with those of the pure components and could be predicted by single gas permeability and diffusion coefficients.     

Effect of glucose fouling on the dissolved gases permeation through maximum‐crystallized poly(lactic acid) films

In this study, we investigated the effect of fouling on the dissolved oxygen and carbon dioxide permeation in water through maximum‐crystallized poly(lactic acid) (PLA) films by using proton nuclear magnetic resonance, attenuated total reflection‐Fourier transform infrared spectroscopy, wide‐angle X‐ray diffraction, and ultraviolet–visible spectroscopy, contact angle, water content ratio, and dissolved gas permeation. Fouling means the adhesion of contents on a container's internal surface, where content adhesion can directly influence the barrier property of the container. Glucose, a beverage ingredient, was used as a foulant. The permeation of dissolved gases in amorphous PLA film, maximum‐crystallized PLA film, and fouled maximum‐crystallized PLA film was determined. The decreased interstices in the polymer chains during crystallization resulted in the inhibition of the diffusion and decrease in the permeability coefficient of the gases. Moreover, the slope of the permeability coefficient for carbon dioxide in the Arrhenius plot was found smaller than that of oxygen's. This result indicated that the gas barrier property of dissolved carbon dioxide was considerably influenced by solubility and readily decreases during glucose fouling. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46604.     

Relationship between gas transport properties and fractional free volume determined from dielectric constant in polyimide films containing the hexafluoroisopropylidene group

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     

Gas permeability of copolypeptide membranes composed of γ-methyl L-glutamate and γ-benzyl L-glutamate

Membranes of copoly(γ-methyl L -glutamate, γ-benzyl L -glutamate) (PMBLG) as well as the related homopolymer membranes were prepared, and permeabilities of oxygen, nitrogen, argon, and carbon dioxide were measured in the 0–70°C temperature range. The values of permeability coefficients and solubility coefficients of the copolymers were smaller than those of permeability coefficients and solubility coefficients of the two homopolymers for every gas studied. The diffusion coefficients of the gases showed a minimum at around 25 mole % benzyl glutamate. The temperature at a maximum of tan δ spectra for the membranes showed a maximum at around 25 mole % benzyl glutamate. The Arrhenius plots of diffusion coefficients and solubility coefficients for PMBLG, which contained 50 and 71 mole % benzyl glutamate, showed a break at about 50 and 40°C, respectively. This permeation behavior is explained by assuming a unique interaction between methyl glutamate and benzyl glutamate side chains.     

Influence of silica and black rice husk ash fillers on the diffusivity and solubility of gases in silicone rubbers

The preparation of elastomeric compositions based on poly(methylvinyl siloxane) using silica and rice husk ash as fillers is reported. Permeation of oxygen, nitrogen, carbon dioxide and methane across the compositions was measured in the temperature interval 30-60° C under upstream pressures lying in the range 15-76 cm Hg. Permeation and diffusion coefficients were independent on the upstream pressure but both parameters were thermal activated processes described by the Arrhenius equation. It was found that the activation energy associated with the diffusion process is larger in the filled than in the unfilled rubbers. The results also showed that the fillers enhance gas solubility in polysiloxane compounds in such a way that in most situations the sorption process is exothermic. The analysis of the solubility and diffusivity of gases in the rubbers suggests very good adherence matrix-fillers that hinder micro-Brownian motions thus impeding the normal development of non-permanent holes through which the diffusive particles can easily jump. Neither the proportion nor the nature of the fillers alters the permselectivity characteristics of polysiloxane based compounds.     

Adsorption separation of N2, O2, CO2 and CH4 gases by β-zeolite

In the present study, adsorption equilibrium and kinetic separation potential of β-zeolite is investigated for N₂, O₂, CO₂ and CH₄ gases by using concentration pulse chromatography. Adsorption equilibrium and kinetic parameters have been studied. Henry’s Law constants, heat of adsorption values, micro-pore diffusion coefficients and adsorption activation energies are determined experimentally. The three different mass transfer mechanisms, that have to take place for adsorption to occur, are discussed. From the equilibrium and kinetic data, the equilibrium and kinetic selectivities are determined for the separation of the gases studied.With β-zeolite, carbon dioxide has the highest adsorption Henry’s Law constant at all the temperatures studied, followed by methane, nitrogen and oxygen. Carbon dioxide separation from oxygen, nitrogen and methane has good equilibrium separation factors. This factor is not very high for methane/nitrogen and methane/oxygen systems and is the lowest for nitrogen/oxygen system. Micro-pore diffusion is the dominant mass transfer mechanism for all the systems studied, except CH₄, with β-zeolite. The kinetic separation factors are very small at high temperatures for all the systems studied. Nitrogen/carbon dioxide and oxygen/carbon dioxide can be separated in kinetic processes with reasonable separation factors at low temperatures. Both equilibrium and kinetic separation factors decrease as column temperature increases. Considering all the observations from this study, it was concluded that β-zeolite is a good candidate for applications in flue gas separations, as well as natural gas and landfill gas purifications.     

Molecular dynamics simulation of diffusion and permeation of gases in polystyrene

Molecular dynamics simulations are performed to study the diffusion and permeation of gases, including argon, nitrogen, methane, carbon dioxide, and propane, in polystyrene over a wide range of temperatures. A jumping mechanism is observed for the diffusion of diffusants in polymer. The calculated diffusion coefficients agree well with the experimental data and with the results of former simulation studies. The relation between the diffusion coefficient and the molecular diameter is confirmed by the results. Our calculated results on the temperature-dependence of diffusion coefficients show that for some gases a break is seen, at the glass transition temperature, in the Arrhenius plot of ln (D) versus 1/T, while for some other light gases, argon and nitrogen, the plot is linear over the whole temperature range. We have also calculated the permeability coefficients, using the diffusion coefficients calculated in this work and our recently published solubility coefficients [Eslami and Müller-Plathe, Macromolecules 2007; 40:6413]. Our results show that the calculated permeability coefficients are higher than the experimental data by almost the same trend observed in the solubility calculations, but the ratios of calculated permeabilities are in a very good agreement with experiment.     

Adsorption of carbon dioxide in plasma polymers prepared from silicon compounds and carbon dioxide separation membrane

Summary Three silicon compounds, dimethyldimethoxysilane (DMDMOS), decamethylcyclopentasiloxane (DMCPS), and 1,1,3,3-tetramethyldisiloxane (TMDSO), were plasma-polymerized, and the solubility coefficient and the permeation coefficient of carbon dioxide and nitrogen gas were determined. The permeation properties of the deposited films were discussed. The plasma polymers formed from DMDMOS, DMCPS, and TMDSO showed preferential solubility for carbon dioxide. The solubility coefficient of carbon dioxide was closely related to the concentration of Si-(O-)₄ moieties in the plasma polymers. However, these plasma polymers showed no selective permeation of carbon dioxide. The diffusion process rather than the solution process controlled the permeation of carbon dioxide across the plasma polymers. Plasma polymers formed from silicon compounds, if the polymers are less cross-linked, are expected to be a good material for CO₂-selective membrane.     

Gas transport properties in chlorosulfonated polyethylene‐acrylate based adhesives

The permeability and diffusivity properties of four gases—oxygen, nitrogen, carbon dioxide and methane—have been obtained for membranes prepared by the photocrosslinking of a mixture of chlorosulfonated polyethylene, acting as a binder, and a series of acrylic and methacrylic monomers. These measurements have been performed in the range 20°C to 50°C, and the activation energies have also been determined. These data are presented in comparison with those previously obtained in a crosslinked system in which the binder was not chlorosulfonated polyethylene but an aliphatic polyurethane. Both polymeric systems show similar permselectivities for the gas pairs O₂/N₂ (near 5) and CO₂/CH₄ (near 12), though overall permeability is about three times lower in the chlorosulfonated polyethylene—based polymer because of the smaller diffusion coefficients. The permeation and diffusion results are discussed in terms of the final structure of the photocrosslinked polymeric system, and it is concluded that it is the binder which is mostly responsible for the gas transport properties of these crosslinked materials.