Carbon Dioxide Permeability Research Articles

Cellulose Nanocrystals from Lignocellulosic Raw Materials, for Oxygen Barrier Coatings on Food Packaging Films

Cellulose nanocrystals (CNCs) are unique, renewable top-down nano particles from which coatings with improved gas barrier properties and new functionalities can be prepared. In this paper, the potential for obtaining such high performing nanocrystals from low-cost lignocellulosic by-products or raw materials is proved by a comparison study on CNCs obtained both from cotton linters and kraft pulp, by means of the ammonium persulfate (APS) process. Morphological and chemical characterization of the nanocrystals obtained, as well as the main functional properties of the poly(ethylene terephthalate) coated films, showed quite similar characteristics and performances of CNCs obtained from pure cellulose raw material (cotton linters) and the nanoparticles produced from a potential discard of paper making processes (kraft pulp). In particular, the gas barrier properties of the coating produced with CNCs obtained from kraft pulp were very promising, providing oxygen and carbon dioxide permeability values hundreds of times lower than those of equal thickness in comparison with common barrier synthetic polymers, over a broad range of temperatures. The results obtained are relevant not only for the outstanding performances achieved, but also because they evoke a possible positive example of industrial symbiosis in the packaging field, merging together the requirements and needs of the paper and plastic industries and addressing the way towards a better management of waste and materials. Copyright © 2017 John Wiley & Sons, Ltd.

Can the addition of carbon nanoparticles to a polyimide membrane reduce plasticization?

Mixed matrix membranes (MMMs) for carbon dioxide (CO2) separation composed of a commercial aromatic polyimide as a host matrix and carbon nanoparticles as a filler phase have been prepared by a casting method. The solubility of CO2 in the MMM could be predicted within error from the pure component isotherms, suggesting that the sorption of polymer to the nanoparticles did not significantly reduce the availability of sites for CO2 to adsorb. The CO2 permeability increased with filler loading without a reduction in the gas selectivity, reflecting the increase in fractional free volume provided by the carbon nanoparticles. This was reflected in significant changes in the CO2 diffusivity. However, contrary to prior work, the use of the carbon nanoparticles was unable to reduce the effects of plasticisation by either CO2 or water. Changes in the permeability of both water vapor and carbon dioxide occurred with time, particularly for relative humidities beyond 60%. The lack of plasticization resistance may reflect the use of sub-micron nanoparticles rather than larger ones.

Improved mechanical properties, barrier properties and degradation behavior of poly(butylenes adipate-co-terephthalate)/poly(propylene carbonate) films

Poly(butylene adipate-co-terephthalate) (PBAT) was blended with poly(propylene carbonate) (PPC) by a twin screw extruder and then the blends were made onto films via the blown film technique. PPC dispersed uniformly in the PBAT matrix, and the glass transition temperature (T g ) of PBAT were decreased with the increasing content of PPC. Wide angle X-ray diffraction confirmed that the crystallite dimension of PBAT was decreased after blending PBAT with the amorphous PPC. The results of mechanical tests indicated that the PBAT/PPC films showed high tensile strength and tear strength. In addition, the PBAT/PPC films showed high carbon dioxide permeability and moderate oxygen and nitrogen permeability. After embedding in soil, the weight loss and mechanical properties analysis demonstrated that the films were remarkably biodegraded. These findings contributed to application of the biodegradable materials, such as design and manufacture polymer packaging.

Aminosilane-functionalized ZIF-8/PEBA mixed matrix membrane for gas separation application

In this study, bilayer mixed matrix membranes based polyether block amide containing ZIF-8 metal organic nanoparticles, as dispersed particles within the polymer matrix, were synthesized to separate carbon dioxide from methane. To prevent nanocomposite membrane selectivity from a drastic reduction at high loading, the particles were modified by APTMS, APTES. The modified nanoparticles were identified and examined using XRD, BET, DLS, and FTIR. Then the permeability tests were performed with carbon dioxide and methane. A 40 μm thick PES membrane was produced as the base and the PEBA/ZIF-8 MMM with the thickness of about 4 μm as the thin, selectively permeable layer. The APTES-modified ZIF-8 nanoparticles increased forces between the particle surface and polymer chains leading to increased permeability without any significant change in the selectivity. At the loading of 40 wt percentage, the permeability of carbon dioxide significantly improved to 6.7 × 10−8 molm−2s−1pa−1 and selectivity remained about 16.

PBAT/organoclay composite films: preparation and properties

Environmental problems caused by the increased waste associated with short-term use of plastic materials, particularly by the food packaging industry, prompted the search for biodegradable alternatives. This contribution studied one of these alternatives, poly(butylene adipate-co-terephthalate)—PBAT, a polymer that is fully biodegradable in common landfills, compounded with a small amount of Cloisite 20A organoclay. Materials were mixed in a laboratory internal mixer and films prepared in a chill roll extruder. Results show that the presence of organoclay does not increase degradation of the polymer matrix during processing, nor affects its crystallization characteristics. However, organoclay addition significantly diminished oxygen and carbon dioxide permeability of the films, making them a very interesting alternative for the food packaging industry.

Investigation of gas pressure and temperature effects on the permeability and steady-state time of chinese anthracite coal: An experimental study

Understanding permeability evolution in coal is critical for the prediction of coalbed methane (CBM) production and prevention of mine gas disasters. The primary objective of this study is to investigate the influences of gas pressure and temperature on the permeability and steady-state time of a Chinese anthracite coal. Using a self-developed coal and rock steady-state permeability testing system, the permeabilities of Chinese anthracite coal samples with CH4, CO2 and helium were measured under various gas pressures and temperatures. Meanwhile, the relationships between the steady-state time and gas pressure and temperature were examined. The results indicate that the changes of methane and carbon dioxide permeability with respect to gas pressure do not always monotonically increase or decrease. A tendency of an initial decrease, and subsequent increase is observed. For a seepage system, the time required to achieve a steady state increases nonlinearly with the increment of gas pressure, which indicates the typical characteristics of the Langmuir model. If other conditions are held constant, the time required to reach a steady state is longer for higher confining pressures. Carbon dioxide takes longer to reach the steady state than methane. The relationship between permeability and temperature is relatively complicated. Temperature affects the permeability by influencing the thermodynamic expansion of coal, gas molecular dynamics and adsorption/desorption. The actual permeability depends on the influence of the leading factor. We believe that this research will have a substantial guiding significance for field CO2-ECBM and the prevention of mine gas disasters.

Effect of polyelectrolyte on the barrier efficacy of layer-by-layer nanoclay coatings

The development of effective barrier materials is becoming increasingly important, particularly as microelectronic devices and food supplies must be protected for extended periods of time from atmospheric gases and water vapor. One of the most effective, facile, eco-friendly, and inexpensive strategies introduced in this spirit is the sequential buildup of layer-by-layer (LBL) surface coatings. This technology relies on the repeated, alternating deposition of impermeable nanoclay platelets possessing a large diameter-to-thickness aspect ratio and a polyelectrolyte adhesive. Previous studies have focused extensively on the use of polycations for this purpose since they are attracted by the negative charges inherently present on the face of natural nanoclays, such as montmorillonite (MMT). In this work, we compare the barrier properties of LBL coatings prepared with a common polycation and a polyester-based polyanion, which selectively interacts with the positive charges that accumulate on the edges of nanoclay platelets. Deposition of these coatings on a hydrophobic styrenic copolymer is reported here to promote dramatic reductions in the measured permeabilities of oxygen and carbon dioxide. This study, which systematically explores the dependence of single-gas permeability on factors such as MMT suspension concentration, bilayer (BL) coating number and temperature, aims to expand the understanding of LBL coatings by also elucidating morphological considerations.

Gas Permeability and Permselectivity of Poly(L-Lactic Acid)/SiOx Film and Its Application in Equilibrium-Modified Atmosphere Packaging for Chilled Meat.

A layer of SiOx was deposited on the surface of poly(L-lactic acid) (PLLA) film to fabricate a PLLA/SiOx layered film, by plasma-enhanced chemical vapor deposition (PECVD) process. PLLA/SiOx film showed Young's modulus and tensile strength increased by 119.2% and 91.6%, respectively, over those of neat PLLA film. At 5 °C, the oxygen (O2 ) and carbon dioxide (CO2 ) permeability of PLLA/SiOx film decreased by 78.7% and 71.7%, respectively, and the CO2 /O2 permselectivity increased by 32.5%, compared to that of the neat PLLA film. When the PLLA/SiOx film was applied to the equilibrium-modified atmosphere packaging of chilled meat, the gas composition in packaging reached a dynamic equilibrium with 6% to 11% CO2 and 8% to 13% O2 . Combined with tea polyphenol pads, which effectively inhibited the microbial growth, the desirable color of meat was maintained and an extended shelf life of 52 d was achieved for the chilled meat.

Porous hollow fiber membranes with varying hydrophobic–hydrophilic surface properties for gas–liquid membrane contactors

In relation to the demand for asymmetric porous hollow fiber membranes to be used in gas–liquid membrane contactors designed for operation in organic media, polysulfone membranes of this type have been prepared and subsequently modified to impart oleophobic properties to their surface. The structure and properties of the membranes have been characterized using various techniques, such as optical and scanning electron microscopy, and by measuring contact angles and the permeability of helium, carbon dioxide, and hexane. The surface properties of the membranes have been modified by etching with a mixture of hydrogen peroxide and sulfuric acid or coating with a perfluorinated acrylic copolymer. In the latter case, modified membrane samples have shown a significant reduction in wettability with both water and organic liquids. The hexane permeability data indicate the absence of hexane flow through the membrane modified with perfluorinated acrylic copolymer until a gauge pressure of about 1 atm. The results of the study lead to the conclusion that these membranes can find use in gas–liquid membrane contactors, e.g., for the removal of dissolved gases from liquid hydrocarbons.

Simplified Approach Based on Polynomial Equations to Predict the Permeability of Micro‐perforated Polymeric Films

A simplified approach to predict the mass transport properties of micro‐perforated films was presented in this work. In particular, the proposed mathematical model was based on a second‐degree polynomial function. Different types of micro‐perforated films with two thicknesses (35 and 25 µm) were tested for gas and water vapour permeability, under proper conditions. The films differed in both number of holes per unit area and hole diameter. Corresponding non‐perforated films were also tested. The experimental data obtained were used to validate the model. Moreover, the surface response plot of the interactions between hole diameter and number of holes per area relative to oxygen, water vapour and carbon dioxide permeability were determined. Results of the mean relative deviation modulus (E%) between the experimental and predicted data confirmed the ability of the proposed model to predict the permeability of micro‐perforated films. Copyright © 2016 John Wiley & Sons, Ltd.

Aluminophosphate-17 and silicoaluminophosphate-17 membranes for CO2 separations

Aluminophosphate (AlPO)-17 and silicoaluminophosphate (SAPO)-17, for the first time, were made into selective membranes for CO2separations. Pure and submicron SAPO-17 seeds were synthesized using nano zeolite T crystals as silica precursor. Membrane microstructure (thickness and crystal size) and separation performance were strongly affected by the support chemistry and seeds. The selective membranes were prepared by a single hydrothermal synthesis step using the low-cost symmetric macroporous ceramic tubes as substrates. Single-gas and CO2/CH4 mixed-gas permeations through SAPO-17 membranes were investigated as functions of pressure and temperature. Carbon dioxide permeance and CO2/CH4 selectivity were decreased with the increase of pressure and temperature. The best membrane showed the smaller-component permeances of 1.1×10−6 and 8.0×10−7mol/(m2sPa), and mixture selectivities of 53 and 14 for equimolar CO2/CH4 and CO2/N2 mixtures, respectively, at 298K and 0.2MPa pressure drop.

Permeability of carbon dioxide and nitrogen gases through SiO2 and MgO incorporated ENR/PVC membranes

Two mixed-matrix membranes (MMM) for gas permeability test were prepared by introducing inorganic fillers (silica (SiO2) and magnesium oxide (MgO)) in the composite blend of epoxidized natural rubber (ENR) and polyvinyl chloride (PVC). Inclusion of SiO2 and MgO particles in the membranes resulted in pores formation as observed through scanning electron microscopy. Thermal study demonstrated that there were interaction between the fillers and polymer matrix with SiO2 exhibited better interaction. SiO2 was also observed to disperse more evenly in the membrane compared to MgO. The permeability of carbon dioxide (CO2) and nitrogen (N2) gases was measured in order to determine the effects of SiO2 and MgO in CO2/N2 separation performance of the ENR/PVC/filler membranes. CO2 was found to exhibit higher permeability compared to N2 for all the membranes. The gas permeability of ENR/PVC/SiO2 membrane was significantly higher than ENR/PVC/MgO and ENR/PVC membranes. Interestingly, despite having lower permeability, MgO-filled membrane exhibited higher CO2/N2 selectivity. When compared to the Robeson’s upper bound, it was found that introduction of fillers had improved gas separation performance of ENR/PVC membrane.

The effect of temperature on the permeation properties of Sulphonated Poly (Ether Ether) Ketone in wet flue gas streams

Membrane technology can be used to recover high purity water from power station flue gas streams. In this work, the effect of temperature on water vapour and CO2 permeation properties of Sulphonated Poly (Ether Ether) Ketone (SPEEK) with two different ion exchange capacities were investigated (IEC 1.6meq/g and 1.9meq/g). It was found that both permeabilities increased with increasing water activity due to increased water solubility as water concentration increased. SPEEK with IEC 1.9meq/g exhibited higher water permeability and selectivity than IEC 1.6meq/g. At humidities greater than 50%, both water vapour and CO2 permeabilities also increased as temperature increased up to 50°C due to the increase in diffusion of the penetrating molecules. However as temperature increased further, a significant drop in the permeability of both water and carbon dioxide occurred. This decrease was attributed to the formation of water clusters that filled the free volume in the polymer and hindered the diffusion of isolated molecules. This decrease in diffusion coupled with a reduction in solubility with increasing temperature resulted in the performance decline.

Composite blending of ionic liquid–poly(ether sulfone) polymeric membranes: Green materials with potential for carbon dioxide/methane separation

ABSTRACTThe incorporation of imidazolium‐based ionic liquids into a poly(ether sulfone) (PES) polymeric membrane resulted in a dense and void‐free polymeric membrane. As determined through the ideal gas permeation test, the carbon dioxide (CO2) permeation increased about 22% compared to that of the pure PES polymeric membrane whereas the methane (CH4) permeation decreased tremendously. This made the CO2/CH4 ideal separation increase substantially by more than 100%. This study highlighted the utilization of imidazolium‐based ionic liquids in the synthesis of ionic liquid polymeric membranes (ILPMs). Two different ionic liquids were used to compare the CO2 separation performance through the membranes. The glass‐transition temperatures (Tgs) of ILPMs were found to be lower than the Tg of the pure PES polymeric membranes; this supported the high CO2 permeation of the ILPMs due to the increase in PES flexibility caused by ionic liquid addition. The results also draw attention to new trends of ionic liquids as a potential green candidates for future membrane synthesis. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43999.

Penetrant transport in semicrystalline poly(ethylene furanoate)

Abstract This study investigates the penetrant transport properties of water, oxygen, and carbon dioxide at 35 °C in poly(ethylene 2,5-furanoate) (PEF) isothermally crystallized at 115 and 160 °C. Dual-mode analysis of the water sorption isotherms for the semicrystalline vs. amorphous PEF samples indicates that the Henry’s law sorption parameter ( k D ) is reduced for the semicrystalline samples in direct proportion to the volume fraction crystallinity measured via both density and thermal methods. While the k D for water obeys the simple two-phase model of crystallinity, an unexpected large reduction in the Langmuir capacity constant ( C H ′) for the semicrystalline vs. amorphous samples resulted in an overall reduction in water sorption capacity greater than predicted by the two-phase model. Corroboration of this behavior for water is provided by independent oxygen and carbon dioxide permeation and sorption measurements, which also exhibit larger than expected reductions in solubility for the semicrystalline vs. amorphous samples. This study, which complements prior work, provides an initial look into the effect of crystallinity and morphology on the penetrant transport properties of PEF.

Enzymatically-boosted ionic liquid gas separation membranes using carbonic anhydrase of biomass origin

Nowadays there is a huge demand for new and sustainable technologies aiming the reduction of the greenhouse gas, in particular carbon dioxide emission. In this work, enzymatically-boosted supported ionic liquid membrane (EB-SILM) was developed to permeate carbon dioxide with improved efficiency. Firstly, the selected biocatalyst, carbonic anhydrase (CA) was prepared and purified from spinach, a cheap plant biomass containing the enzyme of our interest. Afterwards, the CA enzyme preparation was used for SILM fabrication in order to test the properties towards enhanced carbon dioxide permeation over CH4, H2 and N2. The results indicate basically that EB-SILMs possess an increased ability to permeate CO2 in comparison with enzymeless controls and therefore, may be viewed as a promising approach e.g. towards enhanced CO2-capture bioprocesses.

Structural, thermal, and gas transport properties of HDPE/LLDPE blend‐based nanocomposites using a mixture of HDPE‐g‐MA and LLDPE‐g‐MA as compatibilizer

Nanocomposites based on high density polyethylene (HDPE)/linear low density polyethylene (LLDPE) blend were prepared by melt compounding in a twin‐screw extruder using organoclay (montmorillonite) as nano‐filler and a 50/50 wt% mixture of maleic anhydride functionalized high density polyethylene (HDPE‐g‐MA) and linear low density polyethylene (LLDPE‐g‐MA) as the compatibilizing system. The addition of a maleated polyethylene‐based compatibilizing system was required to improve the organoclay dispersion in the HDPE/LLDPE blend‐based nanocomposite. In this work, the relationships between thermal properties, gas transport properties, and morphology were correlated. The compatibilized nanocomposite exhibited an intercalated morphology with a small number of individual platelets dispersed in the HDPE/LLDPE matrix, leading to an significant decrease in the oxygen permeation coefficient of the nanocomposites. A decrease in the carbon dioxide permeability and oxygen permeability with increase of nanoclay was observed for the compatibilized nanocomposites. The carbon dioxide permeability of the compatibilized nanocomposites was lower than the carbon dioxide permeability of the uncompatibilized nanocomposites even with the low intrinsic barrier properties of the compatibilizer. These effects were attributed to a good dispersion of the inorganic filler, good wettability of the filler by the polymer matrix, and strong interactions at the interface that increased the tortuous path for diffusion. Theoretical permeability models were used to estimate the final aspect ratio of nanoclay in the nanocomposite and showed good agreement with the aspect ratio obtained directly from TEM images. POLYM. ENG. SCI., 56:765–775, 2016. © 2016 Society of Plastics Engineers

Prediction of gas transport across amine mixed matrix membranes with ideal morphologies based on the Maxwell model

The incorporation of highly selective molecular sieve such as carbon molecular sieve (CMS) and highly affinitive solvent such as diethanolamine (DEA) into polyethersulfone (PES) have been implemented to synthesize amine mixed matrix membranes (MMMs) with an enhanced gas performance. Synergetic effect of CMS and DEA has caused the improvement of carbon dioxide (CO2) permeability and ideal CO2/CH4 selectivity. While existing theoretical models define the relative permeability well for binary mixed matrix membranes they fail to predict the relative permeability of amine mixed matrix membranes. In fact, the degree of deviation from the simple model predictions provides understanding into the detailed properties of the third component, which has been neglected in previous analyses of these models. Modification of an existing model, namely the Maxwell model, provides an outline to analyze the gas permeation properties of model systems with CMS and DEA in glassy polymer phase. The new model is developed by modifying the basic Maxwell MMMs model. The modification also includes the optimization of λdm, which is defined as the ratio of dispersed phase permeability to matrix permeability, and the determination of permeability of the dispersed phase. Furthermore, this Maxwell model has been extended to model the performance of amine mixed matrix membranes by incorporation of combined volume fraction of filler and amine φ*ad. The proposed approach can predict the permeability of CO2 through amine MMMs and also lowers the AARE % value.

Self-assembly of tissue spheroids on polymeric membranes.

In this study, multicellular tissue spheroids were fabricated on polymeric membranes in order to accelerate the fusion process and tissue formation. To this purpose, tissue spheroids composed of three different cell types, myoblasts, fibroblasts and neural cells, were formed and cultured on agarose and membranes of polycaprolactone (PCL) and chitosan (CHT). Membranes prepared by a phase-inversion technique display different physicochemical, mechanical and transport properties, which can affect the fusion process. The membranes accelerated the fusion process of a pair of spheroids with respect to the inert substrate. In this process, a critical role is played by the membrane properties, especially by their mechanical characteristics and oxygen and carbon dioxide mass transfer. The rate of fusion was quantified and found to be similar for fibroblast, myoblast and neural tissue spheroids on membranes, which completed the fusion within 3 days. These spheroids underwent faster fusion and maturation on PCL membrane than on agarose, the rate of fusion being proportional to the value of oxygen and carbon dioxide permeances and elastic characteristics. Consequently, tissue spheroids on the membranes expressed high biological activity in terms of oxygen uptake, making them more suitable as building blocks in the fabrication of tissues and organs. Copyright © 2015 John Wiley & Sons, Ltd.

Permeation of water vapour, nitrogen, oxygen and carbon dioxide through whey protein isolate based films and coatings—Permselectivity and activation energy

The aim of this study was to evaluate the influence of relative humidity (RH) on the oxygen permeability and water vapour transmission rate (WVTR) of whey protein coated Polyethylene terephthalate (PET) or whey protein monolayer films. Furthermore, the activation energies for the permeability of oxygen, carbon dioxide and nitrogen as well as the permselectivities under different set of temperatures were measured. The results showed that the permeability values through the whey protein coating and whey protein film increased with increasing RH. The water vapour permeability measured at 50% RH of (9.3 ± 0.6)−10 cm3 (STP) cm cm−2 s−1 Pa−1 increased to (16.2 ± 0.9)−10 cm3 (STP) cm cm−2 s−1 Pa−1 at 85% RH. An increase in temperature showed an expected increase of the permeability in both uncoated PET and the whey protein monolayer. The permselectivity of whey protein film was determined and the calculated ratios of the permselectivity (P(N2)/P(O2)/P(CO2):1/(4–6/(34–35)) differed from the simplified ratios given in the literature (P(N2)/P(O2)/P(CO2):1/4/16). Furthermore the calculated activation energy values for whey (51 kJ mol−1) were in agreement with other studies.