Gas Permeability Values Research Articles

Layer-by-layer assembled graphene oxide/polydiallydimethylammonium chloride composites for hydrogen gas barrier application

Poly(diallyldimethylammoium chloride) (PDDA)/acid or base modified graphene oxide (MGO) composite (PDDA/MGO)-based gas barrier films were prepared by layer-by-layer (LBL) assembly method on polyethylene terephthalate (PET) substrate using a spray coating assisted deposition. The effect of pH on the hydrogen gas permeability (H2GP) values of the different MGO-based films was investigated to determine the optimum pH value of the MGO solution for the preparation of PDDA/MGO-based LBL assembly. Accordingly, the different numbers of bilayers based LBL-assembled films were prepared using alternate deposition of PDDA and MGO solutions and the H2GP values were measured for those assemblies. The films were characterized by XRD, FT-IR, and Raman spectroscopy analyses. The morphology of the LBL-assembled film was observed by cross-sectional field emission scanning electron microscopy which confirms densely packed layered structure. The H2GP of six bilayers PDDA/MGO composite film is 5.7 cc/m2⋅d⋅atm, which is much lower than that of pure PET substrate (170.7 cc/m2⋅d⋅atm), indicating 96.7% decrease in H2GP. This result suggests that the PDDA/MGO composite film could be used as a potential candidate to fabricate hydrogen gas barrier coating material.

Effect of organoclay-type and clay-polyurethane interaction chemistry for tuning the morphology, gas barrier and mechanical properties of clay/polyurethane nanocomposites

Abstract Organo-modified montmorillonite (Mt) and bentonite reinforced clay/polyurethane nanocomposite (CPN) films were produced by master-batch based melt-mixing route, followed by compression molding. A novel route for preparation of master-batch by solution mixing was explored by using sonication and high-speed stirring. It was found that master-batch prepared by solvent mixing route resulted in good dispersion of clay-platelets in master-batch and finally in CPN. The concentration of both organoclays was varied from 1 to 5 wt% in final CPN, which were prepared by melt-mixing of master-batch and neat polyurethane (PU) in a twin-screw extruder. The presence of hydroxyl group in the clay-modifier of Mt, attributed to nearly exfoliated structure up to 3 wt% due to improved interaction by hydrogen bonding with ether groups or urethane linkages. Whereas, organo-modified bentonite showed partially intercalated and flocculated morphology, due to the absence of any polar group in the clay-modifier. As a consequence, Mt/PU nanocomposites showed much better mechanical and gas barrier properties in comparison to bentonite/PU nanocomposites. Moreover, a significant reduction in helium gas permeability and improvement in mechanical (tensile and tear) properties were observed for CPN produced with both organoclays in comparison to neat PU. At lower volume fraction of organoclays, a good correlation was obtained between gas permeability values determined experimentally and predicted by two different mathematical models.

Fluorinated and sulfonated poly (ether ether ketone) and Matrimid blend membranes for CO 2 separation

Abstract The gas separation performance and miscibility of Matrimid and fluorinated sulfonated aromatic poly (ether ether ketone) (F-SPEEK) blend membranes prepared by solution casting method were studied. F-SPEEK polymer with fixed degree of sulfonation (40%) was used for membrane synthesis. Physical miscibility of both Matrimid and F-SPEEK was observed over the whole composition range, as confirmed by DSC studies and visual observation. The effect of variation in F-SPEEK composition on gas permeability and selectivity of blend membranes was investigated. The gas permeability and selectivity values fall in between those of the individual polymers, varying systematically with variation of F-SPEEK content in the blend. The addition of F-SPEEK in the blend led to simultaneous increase in the gas permeability and selectivity. In order to further study the stability and potential industrial application of these membranes, they were tested at different conditions of feed temperature (298–338 K), feed pressures (10–40 bar) and CO2 concentration in feed. The effect of feed pressure on CO2 permeation was linked to CO2 plasticization of the membranes. The addition of F-SPEEK component in the blend shifted the plasticization pressure thereby imparting anti-plasticization properties to the blend. Improvement in anti-plasticization properties along with enhanced gas separation properties confirms F-SPEEK/Matrimid blend membranes as an excellent candidate for the separation of gaseous mixtures at industrial scale.

Monolayer and bilayer graphene on polydimethylsiloxane as a composite membrane for gas‐barrier applications

ABSTRACTWe report the preparation of centimeter‐scale composite membranes formed by monolayer or bilayer graphene and polydimethylsiloxane (PDMS). Graphene was synthesized on copper foils by chemical vapor deposition (CVD), and two methods for transferring the graphene layers from the Cu to the PDMS were tested. The method based on the use of poly(methyl methacrylate) as a sacrificial support layer was more effective in producing membranes with significant gas‐barrier properties, in which the gas permeability values for CO2 and N2 were reduced by up to 30% as compared to blank PDMS membranes. Raman spectroscopy maps and atomic force microscopy revealed that, on the microscopic scale, graphene is preserved upon transfer, but the presence of extended defects such as folds and tears still limits further increases in the composite barrier properties. The deleterious effect of such defects is reduced by using more than one graphene layer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45521.

Effects of nano-silica on the gas permeability, durability and mechanical properties of high-strength lightweight concrete

This study presents an experimental investigation on the effect of nano-silica (nS) on the gas permeability, durability and mechanical properties of high strength lightweight concrete (HSLWC). In order to expose the effects of nS on the performance of concrete, the lightweight coarse aggregate (LWA) has been fabricated through cold bonded method by the pelletization process by mixing 10% of cement with 90% of fly ash (FA). Then, the utilization of HSLWCs has been finished off by volumetric substitution of normal coarse aggregate with 5 different levels, namely (0%, 10%, 20%, 30% and 40%) with and without nS at a constant water/binder ratio of 0.35 and a constant ratio of 20% of FA. The concrete has been tested at the age of 28 and 90days for splitting tensile strength, sorptivity index, gas permeability and compressive strength as well as 3 and 7days for compressive strength. It has been observed that the increase in the replacement of lightweight coarse aggregate affecting the strength and permeability properties negatively. On the other hand, the results indicate that the addition of 3% nS to HSLWCs reduce the negative properties of lightweight coarse aggregate and leads to remarkable increase in mechanical properties while the sorptivity and gas permeability values have been decreased up to 25% and 40% respectively, when the values compared with the same replacement levels of LWAs. Moreover, it has been found that nS particles have better results on normal concrete compared to the LWCs.

Cyclic electrophoretic deposition of electrolyte thin-films on the porous cathode substrate utilizing stable suspensions of nanopowders

In this study, nanopowder Се0.8(Sm0.75Sr0.2Ba0.05)0.2O2−δ (CSSBO) with average diameter of particles of 15nm and specific area of 53m2/g prepared by the method of laser evaporation was used for a cyclic electrophoretic deposition (EPD) from a non-aqueous suspension on a functionally graded cathode substrate with a LaNi0.6Fe0.4O3−δ (LNFO) collector layer and a La2NiO4±δ (LNO) functional layer. Thick LNFO support (1mm) with 20% of pore former had a porosity of 45% after sintering at 1400°С. The values of gas-permeability which was measured by means of the computerised experimental set, varied from 31.60×10−3 to 25.71×10−3μm2. A thin LNO functional layer was brush painted on the top of the support and pre-sintered at 1350°С, 2h. Green CSSBO film with a thickness of 8μm was stepwise deposited on the graded cathode substrate and sintered at 1400°С, 4h. The critical load for fracture of the film (approximately 5μm thick after sintering) was 111±14mN, conductivity was equal to 2.40×10−2S/cm at 750°C.

Validation of a predictive model coupling gas transfer and microbial growth in fresh food packed under modified atmosphere

Predicting microbial safety of fresh products in modified atmosphere packaging implies to take into account the dynamic of O2, CO2 and N2 exchanges in the system and its effect on microbial growth. In this paper a mechanistic model coupling gas transfer and predictive microbiology was validated using dedicated challenge-tests performed on poultry meat, fresh salmon and processed cheese, inoculated with either Listeria monocytogenes or Pseudomonas fluorescens and packed in commercially used packaging materials (tray + lid films). The model succeeded in predicting the relative variation of O2, CO2 and N2 partial pressure in headspace and the growth of the studied microorganisms without any parameter identification. This work highlighted that the respiration of the targeted microorganism itself and/or that of the naturally present microflora could not be neglected in most of the cases, and could, in the particular case of aerobic microbes contribute to limit the growth by removing all residual O2 in the package. This work also confirmed the low sensitivity of L. monocytogenes toward CO2 while that of P. fluorescens permitted to efficiently prevent its growth by choosing the right combination of packaging gas permeability value and initial % of CO2 initially flushed in the pack.

High performance cyclic olefin copolymer (COC) membranes prepared with melt processing method and using of surface modified graphitic nano-sheets for H2/CH4 and H2/CO2 separation

In this study, cyclic olefin copolymer (COC) composite membranes were prepared with melt processing method by using of various types of graphite nano-sheets namely graphite oxide (GO), octadecylamine (GO-ODA) and stearic acid (GO-SA) modified graphite oxides. Structural and physical characterization of the modified nano-sheets and membranes were conducted by contact angle measurements, XRD, FTIR, TGA, DMA and SEM analysis. Gas permeability (P) and ideal gas selectivity values (α) of membranes for the H2/CO2 and H2/CH4 were quantified depending on the structural features and the content of fillers. It was found that increasing amount of filler resulted in reducing of CO2 and CH4 permeability for all series of membranes. On the other hand, the H2 permeability values of membranes decreased with the increasing amount of filler in the sample series prepared with GO and GO-ODA but increased in the samples containing of GO-SA. It was also found that the ideal selectivity values of the membrane included 5wt% of GO-SA for the H2/CH4 and H2/CO2 were drastically improved to 498 and 38.6, respectively. Consequently, the ideal selectivity of GO-SA base membrane was increased by 57.5% for H2/CO2 and by 280% for H2/CH4 separation compared to the COC film. The superior separation performances of the system surpass the current permeability–selectivity tradeoff limits (Robeson, 2008 upper bound) for H2/CO2 separation.

In-plane gas permeability and thought-plane resistivity of the gas diffusion layer influenced by homogenization technique and its effect on the proton exchange membrane fuel cell cathode performance

In this study, in-plane gas permeability and through-plane resistivity of gas diffusion layer (GDL) made by different microporous layers (MPLs) were characterized by a new combined measurement setup under different compression ratios. Applied MPL ink-homogenizing techniques were pulse sonication, continuous sonication, bath ultrasonic and mechanical stirring. Results showed that 20% GDL compression produced optimized in-plane gas permeability and through plane resistivity, which is suitable for application in proton exchange membrane fuel cell (PEMFC). However, bath ultrasonic technique is more desirable technique for MPL ink homogenization in term of obtained gas permeability and total resistivity values; 0.45 (×10−12 m2) and 2.63 (mΩ cm2) respectively.Morphological investigation was also presented a uniformly distributed MPL microstructure without large cracks for the MPL which was prepared by bath ultrasonic technique (MPL-C).The Obtained results in H2/air PEMFC under various cathode relative humidity (RHC), 33–100%, revealed that the performance of the MEA made by MPL-C is 20% higher than others; 504 mWcm−2 versus 385 mWcm−2at 33% RHC. More analysis by electrochemical impedance spectroscopy demonstrated that MPL ink preparation by bath ultrasonic techniques resulted a lower ohmic and charge transfer resistance in PEMFC at least in small scale MEA.

Comparing of melt blending and solution mixing methods on the physical properties of thermoplastic polyurethane/organoclay nanocomposite films

In this study, microstructural features and physical properties of thermoplastic polyurethane (TPU)/organoclay nanocomposites films prepared via melt blending (MB) and solution mixing (SM) methods were investigated in detail. Amount of organoclay into the composition varied in the range of 2 and 8 wt%. Microstructural properties of samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) methods. It was found that the organoclay layers exhibited better dispersion, exfoliated, and semi-exfoliated structure in the MB samples than the SM counterparts. Viscoelastic properties of samples were also studied by measuring the rheological behaviors of bulk samples in an oscillatory rheometer in the melt state and measuring of the time-dependent nonlinear creep behaviors of film samples in a dynamic mechanical analyzer in the solid state. Gas and water vapor permeability (WVP) values of nanocomposite films were measured. Based on the melt rheology measurements, it was found that the MB samples showed characteristic solid-like behavior and higher improvement in storage modulus at low-frequency region. Creep behaviors of samples were also quantified with the four-element Burger model. It was found that the introducing of organoclay into the composition via MB method yielded more improvement in the creep resistance, gas, and WVP values of films than the SM counterparts, possibly due to the better dispersion of organoclay layers into the TPU structure. Based on the improvement in permeability and mechanical properties of the samples and also SEM and TEM observations, the average aspect ratio value ( Af) of organoclay stacks was estimated in the range of 15–20 for the MB samples.

Study on the Properties of UHMW-PE Film

Some physicochemical properties of UHMW-PE film such as gas permeability, tensile strength, and corrosion resistance in acid with different immersion time, various concentrations and various solutions and rattler testing were studied. The obtained results showed that the values of gas permeability, tensile strength, elongation at break, and the temperature of dissociation at weight loss 5% was 546.57 cm3·m﹣2·24 h·0.1 MPa, 37.22 MPa, 368.00%, 360°C, respectively. In different concentration acid, the surface resistance of film accumulated to some extent with immersion time increasing, together with that the higher acid concentration was, the lower the surface resistance of film was. Moreover, the contact angle of films gradually increased with the acid concentration decreasing and the increase of immersion time. After wear testing, the mass of UHMW-PE film did not nearly change, while the contact angle became larger with the number of turning increasing and the value was more than 90°.

On the Reverse Asymmetric Gas Transport Effect in the Polymer Membranes

In this paper, change of gas permeability value, depending on orientation of polymer gas membrane, in a wide pressure range was investigated. Consistent patterns of asymmetric gas transfer through the PVTMS-membrane were established experimentally. Reverse asymmetric transport effect was observed, wherein the permeability from the direction of porous support prevails at the permeability from the direction of selective non-porous layer.

Experimental and Theoretical Study of [2σ + 2σ + 2π]–Cycloaddition of Quadricyclane and Ethylenes Containing Three Silyl-Groups

The reaction of [2σ + 2σ + 2π]-cycloaddition of quadricyclane with olefins is an attractive way for regio- and sterospecific synthesis of norbornene derivatives (exo-tricyclononenes) with desired substituents. The presence of Cl3Si-containing groups in such compounds permits different monomer modifications for the development of new materials. Herein, for the first time the theoretical and experimental study of the behavior of different ethylenes containing three silyl-groups in the reaction of [2σ + 2σ + 2π]-cycloaddition with quadricyclane was systematically performed. Based on the data obtained for this reaction the activity scale of the ethylene derivatives was established, and the explanations for an ethylene activity were suggested. As a result, a new family of Si-containing tricyclononenes was successfully synthesized. As an example of a possible modification, the methylation of the sterically hindered cycloadducts was investigated and the conditions for full methylation were found. Considering that gas permeability of polymers increases with the increase of a number of the side Me3Si-groups, the compounds are interesting monomers for synthesis of membrane polymers possessing high gas permeability values.

Crosslinking of gelatin membranes with ferulic acid or glutaraldehyde: Relationship between gas permeability and renaturation level of gelatin triple helices

ABSTRACTThis study investigated the gas separation membranes made with gelatin, crosslinked with ferulic acid (FA) and blended with polyethylene glycol (PEG) 200, by using a solvent‐free procedure. Gas permeation properties (He, N2, O2, and CO2) of these “green membranes” were studied and discussed in relation with their structure. Differential scanning calorimetric measurements were carried out to determine the gelatin triple helical renaturation level. The lowest permeability values [He and CO2 permeability (4.5 × 10−2 Barrer) with CO2/O2 selectivity of 14.5] were reached with gelatin/PEG 200 uncrosslinked membranes showing the highest renaturation level (40%). Crosslinking with FA lead to less rigid and brittle materials than GTA and to 10 times more permeable membranes compared with uncrosslinked membranes. Membranes crosslinked with glutaraldehyde broke during gas permeation measurements. Results demonstrated that higher gas permeability values were closely related to lower renaturation level of gelatin. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 280–287

Preparation of dense gelatin membranes by combining temperature induced gelation and dry-casting

The purpose of this work was to develop a methodology to establish the phase diagram of a binary gelatin/water system in order to study the elaboration process of gelatin membranes. The process involved dry-casting of gelatin solutions, temperature induced gelation (TIG) and membranes drying. The sol/gel transition was measured by rheological measurements and a novel methodology coupling thermogravimetric analyses and extensional rheology was established to determine the gel/membrane transition. By means of this process, called “TIG/dry-cast”, dense gelatin membranes were prepared. Gas permeability values for He, CO2, N2 and O2 of gelatin based films were measured for temperatures ranged between 25°C and 90°C. The relatively low permeability values (<1.5Barrer) with interesting selectivity coefficients for CO2/O2 of about 10 between 25°C and 40°C made these membranes more suitable for thin layer deposition onto porous support for gas separation applications. All these results confirmed that gelatin is a promising biobased polymer for membrane preparation. The methodology developed in this paper can be applied to other gelatin/water systems to establish their phase diagram.

Clustering of Composite Protein Films and their Packaging Properties

Cases of 30 whey protein isolate-sodium caseinate-glycerol composite protein films based on different ingredients and processing techniques, and their packaging properties were analyzed by Q and R cluster analysis, respectively. The results verified that there was a correlation in either 30 cases or 7 indexes of packaging performance, which contributed to a scientific sorting. 30 cases could be divided into 5 groups by Q cluster analysis with the Euclidean distance at 40, in which case 28 and 30 exhibited the highest similarity. On the other hand R cluster analysis in packaging performance indicated that gas permeability and haze values of composite films tended to be more similar than the others.

Bionanocomposites of Cassava Starch and Synthetic Clay

Starch-based biofilms containing synthetic Laponite clay and glycerol were prepared using a solvent casting technique. Electron microscopy images showed predominance of the exfoliated type of nanocomposite. Dynamic mechanical analysis revealed a larger influence of glycerol content on the polymer β relaxation and T g than the clay content. Gas barrier properties were influenced by clay particles and plasticizer content. An increase of clay content led to lower gas permeability values. Although both glycerol and Laponite are hydrophilic, no significant changes were observed on the water sorption by starch films at different relative humidity values. Mechanical properties are kept similar after the inorganic filler incorporation.

The effect of trimethylsilyl substituents in the monomer unit on the energy characteristics of surfaces of polynorbornenes obtained via metathesis polymerization

The surface properties of polynorbornenes obtained via metathesis polymerization are investigated via the wetting method. The incorporation of trimethylsilyl groups into the monomer unit causes decreases in the specific free surface energies of the investigated polymers. It is found that the dispersion terms of the specific free surface energies correlate with the free-volume and gas-permeability values of the polymers. As shown through the methods of differential scanning calorimetry and FTIR spectroscopy, during heating in air, the considered polynorbornenes undergo oxidative crosslinking, which increases their specific free surface energies. The interphase energies of crosslinked polynorbornenes are determined at their interfaces with liquids modeling polar and nonpolar phases, and the values of the work of adhesion of the crosslinked polynorbornenes to the model liquids are calculated. It is shown that the work of adhesion of the polymer to the polar phase decreases after introduction of trimethylsilyl groups, while the combination of polar and nonpolar phases give rise to an increase in the work of adhesion.

Study on the Longitudinal Permeability of Oil Palm Wood

In this research, variations in longitudinal permeability of oil palm (Elaeis guineensis Jacq) wood were investigated. Panels were prepared from bark to pith with the study carried out on 3 parts of the transverse surface: outer, middle, and inner. Microscopic observations were done to determine the anatomical properties to establish its theoretical permeability using Poiseuille’s equation. Results showed that the middle part of the transverse surface of oil palm wood had the highest theoretical, water, and gas permeability values in the longitudinal direction followed by the inner and outer parts. A decrease in the length of samples resulted in an increase in the permeability of the samples. For all parts, theoretical permeability values were the highest followed by water and gas permeability Lower gas permeability values in comparison to water permeability indicates that oil palm wood is prone to drying defects and is more difficult to treat with chemicals after drying.

Experimental investigation of the sealing capacity of generic clay-rich caprocks

For a set of generic clay-rich lithotypes, gas breakthrough experiments with helium (He) and carbon dioxide (CO2) were conducted at elevated pressures and temperatures. Core plugs of 38mm diameter and approx. 15mm length were prepared and measurements were performed at confining pressures between 15 and 29MPa and temperatures of 25–45°C. Intrinsic permeability coefficients of the samples ranged between 3×10−18 and 2×10−22m2.Gas breakthrough and subsequent viscous gas flow could only be achieved for an argillaceous limestone and two mudstone samples with intrinsic permeability coefficients of 4×10−18 and 2×10−20m2, respectively. For the limestone, capillary gas breakthrough occurred between 1.2 and 2.9MPa (He). The gas (He and CO2) breakthrough pressure for the immature mudstone lay between 5 and 13MPa. Gas flow rates recorded after breakthrough revealed a linear relationship between effective gas permeability and differential pressure. Effective gas permeability coefficients were normalized to single-phase water permeability coefficients to obtain relative permeabilities. The highest relative gas permeability values of approximately 0.05 and 0.10, respectively, for He and CO2 were observed at a differential pressure of 10MPa.The mature shales with intrinsic permeabilities below 10−20m2 represent effective barriers and showed no indications of capillary gas breakthrough up to a pressure difference of at least 20MPa for He and 9MPa for CO2. Gas transport through these caprocks under the conditions of this study occurs only by diffusion, with average diffusion coefficients in the order of 10−11m2/s.Analyses of the sample plugs after exposure to CO2 revealed no recognizable mineral alterations. This is attributed to the fact that transport and reaction rates are very low and that only a small proportion of the internal surface area is exposed to the permeating fluid/CO2.