Permeability Coefficients Of Carbon Dioxide Research Articles

Effect of graphene oxide/layered double hydroxide modified by 7‐octenyltrimethoxysilane on the mechanical and gas barrier properties of fluoroelastomers

AbstractLayered double hydroxide/graphene oxide (GLDH) composites (SGLDH) modified by 7‐octenyltrimethoxysilane (7‐OTOS) were prepared by co‐precipitation method. The structure and morphology of SGLDH were characterized using x‐ray diffraction, Fourier‐transform infrared spectroscopy (FTIR), x‐ray photoelectron spectroscopy, scanning electron microscopy (SEM), high‐resolution transmission electron microscopy, energy‐dispersive x‐ray spectroscopy, and thermogravimetric analysis. According to the obtained results, 7‐OTOS was successfully grafted onto graphene oxide (GO) and layered double hydroxide (LDH) surfaces. 7‐OTOS was grafted on both GO and LDH surfaces, which is why the amount of LDH loaded on the SGLDH surface was significantly increased compared with that on the GLDH composite. The filler‐matrix interfacial interactions of the SGLDH‐filled fluoroelastomer composites were characterized using contact angle analysis, dynamic mechanical analysis, RPA analysis, FTIR, SEM, and cross‐linking density tests. It was indicated that the interfacial interactions between the SGLDH and matrix were significantly improved, and the SGLDH was well dispersed in the fluoroelastomer composites. In addition, the gas barrier properties and mechanical properties of the fluoroelastomer composites were tested. The carbon dioxide permeability coefficients of the fluoroelastomer composites filled with 10‐phr SGLDH increased by about 32.1% and 20.3%, and the tensile strengths increased by about 47.6% and 27.7%, respectively, compared with those of the fluoroelastomer composites filled with 10‐phr LDH and GLDH.Highlights SLDH nanocomposites are based on silyl ether linkages to increase LDH loading. Elastomer nanocomposites exhibited interfacial cross‐linking mechanism. Interfacial interactions were exhibited between FKM and SGLDH. FKM/SGLDH exhibited enhanced gas barrier properties (+32%) compared to FKM. FKM/SGLDH exhibited enhanced mechanical properties (+47%) compared to FKM.

Synthesis and gas permeability of methylol-group-containing Poly(diphenylacetylene)s with high CO2 permeability and permselectivity

Diphenylacetylene monomers bearing a methylol group protected by a t-butyldiphenylsilyl group [tBuPh2SiOCH2C6H4CCC6H4R; R = SiMe3 (1a) and R = SiMe2nC18H37 (1b)] were synthesized and then polymerized with TaCl5/n-Bu4Sn to afford the corresponding poly(diphenylacetylene)s 2a and 2b, respectively. The molecular weights of 2a and 2b were high (i.e., Mw = 1,020,000 and 1,560,000, respectively), and free-standing membranes were obtained by solution casting. The deprotection of membranes of 2a and 2b using n-Bu4N+F− afforded poly(diphenylacetylene)s bearing methylol and silyl groups (3a and 3b). On the other hand, treatment of membranes of 2a and 2b with trifluoroacetic acid led to deprotection and desilylation, producing poly(diphenylacetylene)s bearing trifluoroacetate moieties (4a and 4b, respectively), and then treatment with methanol afforded poly(diphenylacetylene)s bearing only methylol groups (5a and 5b). The carbon dioxide permeability coefficients (PCO2) of membranes of 2a and 2b were 99 and 78 Barrer, respectively. Deprotection led to the increment of CO2 permeability without the decline of the CO2 permselectivity. Poly(diphenylacetylene)s bearing methylol and silyl groups (3a and 3b) exhibited high permeability (PCO2 = 2000 and 120 Barrer, respectively), but not high permselectivity (PCO2/PN2 = 17 and 16, respectively). Methylol-group-containing poly(diphenylacetylene) without silyl groups 5b exhibited the best CO2 permeation property, i.e., high CO2 permeability and high permselectivity (PCO2 = 220 Barrer, PCO2/PN2 = 32).

ポリテトラヒドロフランアイオネンの気体透過性と二酸化炭素分離膜としての評価

Gas permeability of ionene polymers (PTIs) containing poly(tetrahydrofuran) [PTHF] soft-segment blocks (the molecular weight of PTHF block: 1100 and 2300) and viologen hard ionic segments (counter anion: Cl−, Br−, and I−) were investigated. The gas permeability coefficients of carbon dioxide (PCO2) and the CO2 and N2 separation factor (PCO2/PN2) of PTI having the 2300-PTHF block molecular weight and Cl− counter anion were 201 barrer and 30, respectively, indicating that PTI is a good candidate for CO2 separation membrane polymer.

Highly CO2-permeable and -permselective poly(diphenylacetylene)s having imidazolium salts: Synthesis, characterization, gas permeation properties, and effects of counter anion

Diphenylacetylenes having a 2-bromoethoxy group [p-(BrCH2CH2O)C6H4CCC6H4-p-R; R = SiMe3 (1a), H (1c)] were synthesized and then polymerized with TaCl5/n-Bu4Sn catalyst to provide the corresponding poly(diphenylacetylene)s (2a and 2c). These polymers afforded tough free-standing membranes by casting from toluene solutions. Substitution of 1-methylimidazole to the membrane (2a) gave an imidazolium salt-containing poly(diphenylacetylene) [3a (Br−)]. Membrane of 3b (Br−) was obtained by desilylation of 3a (Br−) using HBr. Counter anions of 3a (Br−) could be exchanged by the treatment of the membrane with CF3COOK and (CF3SO2)2NLi, and the membranes 3a (TFAc−) and 3a (Tf2N−) were obtained. The carbon dioxide permeability coefficients (PCO2) of membranes of 2a and 2c were 250 and 21 barrers, respectively. The PCO2/PN2 values of 2a and 2c were 16 and 11, respectively, which are ordinary values among all the polymers. In contrast, introduction of 1-methylimidazole into the membranes remarkably increased the CO2/N2 selectivity (PCO2/PN2 = 31–44), although the CO2 permeability decreased. The increase in the CO2/N2 selectivity was attributed to the significant increase of CO2/N2 solubility selectivity. The PCO2 values of 3a (Br−), 3a (TFAc−), and 3a (Tf2N−) were 11, 23, 53, respectively, indicating that the CO2 permeability increased as the counter anion became bulkier.

Molecular modeling investigation of the fundamental structural parameters of polymers of intrinsic microporosity for the design of tailor-made ultra-permeable and highly selective gas separation membranes

Molecular dynamics techniques have been used to investigate the pronounced permeability and selectivity of polymers of intrinsic microporosity (PIM). While helium exhibited greater permeability coefficients due to higher diffusivity resulting from its small molecular size, the higher permeability coefficients of carbon dioxide were attributed to the favorable values of the enthalpy of mixing of the gas molecules with the polymeric chains. The simulation results also showed that the fractional free volume and the Connolly surface of the PIMs had greater values resulting from the inability of the rigid and contorted structures of the PIMs to pack space efficiently and thus creating interconnected nanochannels throughout the matrix of the polymers of microporosity. Replacing the heteroatoms of the PIM with carbon atoms resulted in a major decrease in the fractional free volume with a corresponding decline in the diffusion coefficients whereas replacing the site of contortion with a flexible methylene group did not have much effect. Attaching alkyl side groups to the polymeric chains was shown to reduce the free volume as a result of the side chains filling the voids of the micropores. The results were employed in the design of tailor-made membranes for use in the separation of natural gas components.

Synthesis of poly(p-phenyleneethynylene)s bearing oligo-ethylene glycols and their gas permeation properties

1,4-Diiodobenzenes bearing oligo-ethylene glycols [IRC6H2IR, R = OCH2CH2OCH3 (1a), O(CH2CH2O)2CH3 (1b), O(CH2CH2O)3CH3 (1c)] were polymerized with 1,4-diethynylbenzene in the presence of Pd/Cu catalyst to afford poly(p-phenyleneethynylene)s bearing oligo-ethylene glycols (2a–c), respectively. Polymer 2a was insoluble in any solvents, but the other polymers (2b, 2c) were soluble in CHCl3. The weight-average molecular weights of 2b and 2c were 5.4 × 104 and 9.6 × 104, respectively, and they gave free-standing membranes by solution-casting method. The densities of membranes of 2b and 2c were 1.26 and 1.22 g/cm3, respectively, and their carbon dioxide permeability coefficients were 12.9 and 13.5 barrers, respectively. The CO2/N2 separation factor of membrane of 2b was as large as 33.7. Membrane of 3b, which contains triethylene glycols, exhibited higher CO2 permselectivity, and the CO2/N2 separation factor was 50.0.

Effect of moderate electric fields in the permeation properties of chitosan coatings

Edible films and coatings can provide additional protection for food, while being a fully biodegradable, environmentally friendly packaging system. Preliminary works have shown that the presence of a moderate electric field during the preparation of chitosan coating solutions may influence e.g. their transport properties. If such effect is confirmed, moderate electric fields could be used to tailor edible films and coatings for specific applications. The aim of this work was to determine the effect of field strength on functional properties of chitosan coatings (obtained from lobster from the Cuban coasts). Four different field strengths were tested (50, 100, 150, 200 V cm −1) and, for each electric field treatment, the water vapor, oxygen and carbon dioxide permeabilities of the films formed were determined, together with their color, opacity and solubility in water. The surface microstructure of the films was analyzed using atomic force microscopy (AFM). The results showed that ohmic heating had statistically significant effects on film's physical properties and structure. In general, the most pronounced effect of the field strength was observed for treatments made at 100 V cm −1 or higher, a positive correlation being found between the water vapor, oxygen and carbon dioxide permeability coefficients and field strength. The AFM results show that the surface of chitosan films is much more uniform when an electric field is applied, which may be related with a more uniform gel structure leading to the differences observed in terms of transport properties.

Influence of postharvest treatments and film permeability on quality decay kinetics of minimally processed grapes

The influence of both postharvest treatments and film permeability on the quality decay kinetics of freshly processed grapes was addressed. Ethanol, chlorinated water and hot water were tested to reduce microbiological spoilage. The treated grapes were packaged in two polyester-based biodegradable films (NVT1 and NVT2) and the composition of the atmosphere within the packages determined. A multilayer film, made by laminating an aluminium foil with a polyethylene film (aluminium) was used to evaluate separately the respiratory activity of the packed grapes, and the oxygen and carbon dioxide permeability coefficients of the investigated films under real working conditions. The quality decay kinetics of freshly processed table grapes packed at 5 °C were assessed by monitoring the cell load of the main spoilage microorganisms (total mesophilic viable count, lactic acid bacteria, yeasts and moulds) and the product appearance for a period of about 30 days. Results suggest that ethanol was the most efficient treatment, as it successfully reduced the cell load of the spoilage microorganisms without affecting respiration of the packed food or its appearance. Differences between the investigated biodegradable films were not statistically significant.

Sulfone‐Containing polymers as high barrier materials

AbstractThree types of sulfone‐containing polymers, poly(carbonate‐sulfone)s, poly(ester‐sulfone)s, and poly(urethane‐sulfone)s, were characterized as high barrier materials. They were made by condensing sulfone‐containing diol, 1,3‐bis(3‐hydroxypropylsulfonyl)propane (Diol‐333), or 1,4‐bis(3‐hydroxypropylsulfonyl)butane (Diol‐343), with diphenyl carbonate, diphenyl esters, and diisocyanates, respectively. The incorporation of polar sulfone groups into polymer backbones increases the glass transition temperature of polymers in all cases; however, the increment is different with different functional linkages. The increments in polycarbonates and polyesters are higher than that in polyurethanes. This is because the interactions between carbonate or ester groups are much weaker than the interactions between sulfone groups, whereas the hydrogen bonding between urethane groups is comparable with the polar interaction between sulfone groups. The polymers were coated on 50‐μm‐thick Kapton films by solution casting and their permeabilities toward carbon dioxide were measured at 25°C using the ASTM D1434 volumetric method. The sulfone‐containing polymers have carbon dioxide permeability coefficients at least 50 times smaller than the corresponding polymers without sulfone groups. The carbon dioxide barrier properties of sulfone‐containing polymers are comparable with ethylene/vinyl alcohol copolymers (EVAL), which are commercial high barrier polymers. An isomer effect on polymer permeability was observed in the aromatic‐aliphatic poly(ester‐sulfone) series. The permeability coefficients of the aromatic‐aliphatic poly(ester‐sulfone)s decrease from terephthalate to isophthalate to phthalate, corresponding to the increase of chain flexibility above the Tg. These results support the hypothesis that high chain flexibility in the rubbery state and a glass transition temperature above room temperature are two key factors that promote low permeability. © 1994 John Wiley & Sons, Inc.

Transport phenomena in gas permeation through glassy polymer membranes with concentration-dependent sorption and diffusion parameters

The modified dual-mode mobility model for permeation of a gas in glassy polymer membranes was combined with the extended dual-mode sorption model to take account of the plasticization effect of sorbed gas molecules on both sorption and diffusion processes. The combined model was further simplified by the introduction of a concentration of the mobile gas species. However, the observed pressure dependence of mean permeability coefficients of carbon dioxide in methylmethacrylate-n-butyl acrylate copolymer and polymethylmethacrylate films at 30°c and also that of oxygen in a polycarbonate film at 50°C and 60°C showed that a plasticization action of sorbed gas species has an influence on the diffusion process rather than on the sorption process, that is, were simulated by the modified dual-mode mobility model combined with the conventional dual-mode sorption model.

Structure and gas permeability of siloxane-imide block copolymer membranes: 1. Effect of siloxane content

Abstract Siloxane-imide block copolymer membranes with various siloxane contents were prepared and their dynamic viscoelasticity, sorption of carbon dioxide, and permeability of carbon dioxide, oxygen and nitrogen were studied. The siloxane-imide block copolymer consists of a microphase separated structure of imide-rich and siloxane phases, and the mechanical properties of the siloxane-imide block copolymer are well retained up to a siloxane content of about 20 wt%. The amount of carbon dioxide sorbed into the siloxane-imide block copolymer decreases with the introduction of siloxane, reflecting the less-sorptive capability of the siloxane group. The sorption behaviour of the block copolymers is interpreted in terms of a dual-mode sorption theory, which is applied to glassy imide-rich phases. On the other hand, the permeability coefficients of carbon dioxide, oxygen and nitrogen are remarkably increased with siloxane content when the latter is more than 10 wt%, and the permselectivity of oxygen to nitrogen is decreased with siloxane content. These behaviours are interpreted by considering the arrangement of the two phases in the membrane.

Mechanism of gas permeation through glassy polymer films

The observed pressure dependence of the mean permeability coefficients of carbon dioxide and methane in glassy polymer films such as polycarbonate, Kapton® polyimide and polysulfone, taken from existing papers, was compared with the predictions in terms of a dual-mode mobility model and a modified mobility model in which both the Henry's Law and Langmuir populations execute four kinds of diffusive movement. The pressure dependence is simulated better by the modified model than by the original model. The mean permeability coefficients and sorption isotherms for carbon dioxide and methane in commercially available polysulfone films were measured at four temperature levels between 30 and 45°C and at gas pressures up to 33 atm and 61 atm, respectively. The pressure dependence of the mean permeability coefficients for the above systems is also described well by the modified mobility model, whereas the sorption isotherms are described well by the dual-mode sorption model.