The transport properties of CO2 and CH4 for brominated polysulfone membrane

The sorption and permeation properties of CO₂ and CH₄ for synthesized brominated polysulfone, BPSf (bromobisphenol A polysulfone) were measured, and compared with the values for PSf (bisphenol A polysulfone), MPSf (bisphenol A methylated polysulfone) and TMSPSf (bisphenol A trimethylsilylated polysulfone) to investigate the structure-property relationships. Especially, the effect of polarity of substituents on the transport properties was studied. The effect of operating pressure on the permeation properties of polysulfones was examined. The permeation properties for a mixture of CO₂ and CH₄ were also measured, and these results were compared with those obtained from the experiments of pure gases. The sorbed concentrations and permeability coefficients are well fitted to the dual mode model. The permeability coefficients of each gas of a binary mixture are less than those of pure gases, and the extent of reduction in permeability coefficient is larger for less permeable polymer. The ideal separation factor for four polysulfones increases in the following order: TMSPSf< PSf< BPSf< MPSf. The ideal separation factor for BPSf is higher than other polysulfones having similar permeability coefficients of CO₂ with BPSf. It can be explained that the strong polarity of bromine in BPSf increases cohesive energy density of polymer, and reduces the chain packing-inhibiting ability. The ranking of permeability coefficient correlates well with fractional free volume. The variation of d-spacing is not consistent with the permeability coefficient.     

The transport properties of CO2 and CH4 for chemically modified polysulfones

The sorption and transport properties of pure CO₂ and CH₄ for a series of polysulfones were measured. The effects of molecular structure of polysulfones on transport properties were studied using chemically modified polysulfones, including TMSPSF (bisphenol‐A trimethylsilylated polysulfone), BPSF (bromobisphenol‐A polysulfone), and BTMSPSF (bromobisphenol‐A trimethylsilylated polysulfone). The effects of operating pressure on the sorption and permeation properties of polysulfones were examined. The permeation properties for a mixture of CO₂ and CH₄ were also measured and these results were compared with those obtained from the experiments of pure gases. The sorbed concentrations and permeability coefficients are well fitted to a conventional dual‐mode model. The permeability coefficients of each gas of a binary mixture are lower than those of pure gases, which shows the competition effect between each component. The permeability coefficients of polysulfones rank in the following order, TMSPSF > BTMSPSF > bisphenol‐A polysulfone (PSF) > BPSF. The effect of the substituents on chain packing was related to the gas‐permeation properties. Fractional free volume (FFV) calculations and X‐ray diffraction were used to judge chain packing. In comparison with PSF, the higher values of permeability coefficients for TMSPSF and BTMSPSF are due to higher FFV and d spacing. The lower permeability coefficients for BPSF is attributed to the strong induced dipole interchain interaction. Addition of bromo substituents to TMSPSF is also found to decrease the permeability coefficients for BTMSPSF, suggesting that the potential increase in FFV due to packing–disrupting bulky trimethylsilyl groups is overridden by the increase in cohesive energy density. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 391–400, 2000     

The sorption and permeation of co2 and ch4 for dimethylated polysulfone membrane

The sorption and permeation properties of the CO₂ and CH₄ were measured for polysulfone and dimethylated polysulfone to investigate the structure-property relationships. The effect of operating pressure on the transport properties of the polysulfones was examined. The permeation properties for a mixture of CO₂ and CH₄ (CO₂/CH₄=57.5/42.5 vol%) were also measured and these results were compared with those obtained from the experiments of pure gases. The sorptions of CO₂ and CH₄ are well described by“dual-sorption model”. The permeability coefficients of CO₂ and CH₄ decreases with increasing upstream pressure, as is often the case with other glassy polymers. The permeability coefficients of each gas of binary mixture are reduced than those for pure gases. This result is due to the competition of each gas for the Langmuir sites. The free volume of the dimethylated polysulfone is lower than that of polysulfone, and dimethylated polysulfone shows relatively lower permeability coefficients and higher selectivity than polysulfone.     

Gas permeabilities of CO2 and CH4 for polysulfones substituted with bromo and trimethylsilyl groups

Bromobisphenol A trimethylsilylated polysulfone (BTMSPSf) was synthesized, and the effect of bromo and trimethylsilyl groups on the pure CO₂ and CH₄ transport properties of polysulfone was examined. The ideal separation factor for BTMSPSf is reduced by about 10% than that for unmodified polysulfone (PSf), but BTMSPSf is about two times more permeable than PSf. The effect of the substituents on chain packing was related to the gas permeation properties. Fractional free volume (FFV) calculation, d-spacing and cohesive energy density were used to judge chain packing. In comparison with PSf, the higher values of permeability coefficients for BTMSPSf are due to higher FFV and d-spacing. The small decrease in ideal separation for BTMSPSf is explained as follows: the potential increase in FFV due to packing-disrupting bulky trimethylsilyl groups is overridden by the increase in cohesive energy density attributed to the addition of bromo substituents.     

Preparation and characterization of dimethyldichlorosilane modified SiO2/PSf nanocomposite membrane

Investigations on nanocomposite membranes imply that these hybrid materials recommend promising newgeneration membranes for gas separation in future. In this study, to investigate the effects of preparation parameters on the morphology and gas transport, various parameters including nanofiller content, surface modification and polymer concentration were considered. Two types of fumed silica nanoparticles (nonmodified and modified) were used to study the surface modification effect on agglomeration, void formation and gas separation properties of prepared membranes. Prepared nanocomposite membranes were characterized by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and tensile strength techniques. The gas permeabilities of hydrogen, methane, and carbon dioxide through pure PSf and nanocomposites were measured as a function of silica volume fraction, and permeability coefficients were determined using a variable pressure/constant volume experimental setup. Results showed that gas permeabilities increase with silica content, and proper H₂/CH₄ and H₂/CO₂ selectivities can be achieved with modified type of silica nanoparticles due to inhibition of particle agglomeration and bonding with polymer network. Hydrogen selectivity was improved by using 15 wt% polymer content instead of 9 wt% in preparation of nanocomposite membrane with same silica content. Gas permeation results indicated that increasing of feed pressure from 3 bar to 6 bar has a positive effect on selectivity of H₂/CH₄ but negligible effect on that of H₂/CO₂ for modified silica/PSf membrane.     

Study of transport of pure and mixed CO2/N2 gases through polymeric membranes

The permeations of pure CO₂ and N₂ gases and a binary gas mixture of CO₂/N₂ (20/80) through poly(dimethylsiloxane) (PDMS) membrane were carried out by the new permeation apparatus. The permeation and separation behaviors were characterized in terms of transport parameters, namely, permeability, diffusion, and solubility coefficients which were precisely determined by the continuous‐flow technique. In the permeation of the pure gases, feed pressure and temperature affected the solubility coefficients of CO₂ and N₂ in opposite ways, respectively; increasing feed pressure positively affects CO₂ solubility coefficient and negatively affects N₂ solubility coefficient, whereas increasing temperature favors only N₂ sorption. In the permeation of the mixed gas, mass transport was observed to be affected mainly by the coupling in sorption, and the coupling was analyzed by a newly defined parameter permeation ratio. The coupling effects have been investigated on the permeation and separation behaviors in the permeation of the mixed gas varying temperature and feed pressure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 179–189, 2000     

Gas separation performance of 6FDA-based polyimides with different chemical structures

This work reports the gas separation performance of several 6FDA-based polyimides with different chemical structures, to correlate chemical structure with gas transport properties with a special focus on CO₂ and CH₄ transport and plasticization stability of the polyimides membranes relevant to natural gas purification. The consideration of the other gases (He, O₂ and N₂) provided additional insights regarding effects of backbone structure on detailed penetrant properties. The polyimides studied include 6FDA-DAM, 6FDA-mPDA, 6FDA-DABA, 6FDA-DAM:DABA (3:2), 6FDA-DAM:mPDA (3:2) and 6FDA-mPDA:DABA (3:2). Both pure and binary gas permeation were investigated. The packing density, which is tunable by adjusting monomer type and composition of the various samples, correlated with transport permeability and selectivity. The separation performance of the polyimides for various gas pairs were also plotted for comparison to the upper bound curves, and it was found that this family of materials shows attractive performance. The CO₂ plasticization responses for the un-cross-linked polyimides showed good plasticization resistance to CO₂/CH₄ mixed gas with 10% CO₂; however, only the cross-linked polyimides showed good plasticization resistance under aggressive gas feed conditions (CO₂/CH₄ mixed gas with 50% CO₂ or pure CO₂). For future work, asymmetric hollow fibers and carbon molecular sieve membranes based on the most attractive members of the family will be considered.     

Fluorinated copolyimide membranes for sour mixed-gas upgrading

Three random and two block 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA)-based copolyimides with different 6FpDA:Durene molar ratio varying from 25 to 80% were prepared and characterized. The pure-gas permeation data of their membranes were investigated at 100 psi and 22 °C. The CO₂/CH₄ ideal selectivity coefficient increased to around 47 with the increase of the 6FpDA content to 80% in the copolymer backbone while the CO₂ permeability coefficient found to be the highest (378 barrer) with highest Durene content copolymer. Based on its attractive pure-gas permeation properties(CO₂/CH₄ = 47), 6FDA-6FpDA/6FDA-Durene (4:1) block copolyimide was selected for further analyses, where the effect of pressure and temperature on its gas transport properties was evaluated. Furthermore, the mixed-gas permeation properties were investigated using multicomponent sweet and sour gas mixtures prepared from N₂ (30% or 10%), CH₄ (59%), C₂H₆ (1%), CO₂ (10%), and H₂S (0% or 20%)accordingly. The sweet mixed-gas CO₂/CH₄ selectivity and CO₂ permeability coefficients of 6FDA-6FpDA/6FDA-Durene (4:1) are around 39 and 45 barrer, respectively, at elevated pressure (800 psi). The polymer, however, showed nonideal behavior when subjected to high H₂S-content gas mixture (20 vol. % H₂S), where the CO₂/CH₄ selectivity value dropped to around 21 and the H₂S/CH₄ selectivity coefficient is 13. The CO₂ and H₂S permeability coefficients are 42 and 26 barrer, respectively, at an upstream pressure up to 500 psi. When plotted on the combined acid gas permeability-selectivity curve, the polymer separation efficiency was nearby the high-performing polymers reported in the literature, and way superior to the industrial standard glassy polymer, cellulose acetate, used currently in gas separation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48336.     

Transport properties of gases through integrally skinned asymmetric composite membranes prepared from date pit powder and polysulfone

Studies were conducted on transport properties and separation performance of date pit/polysulfone composite membranes for CO₂, CH₄, N₂, He, and H₂ gases. Date seeds were obtained and processed into powder. Asymmetric flat sheet membrane was prepared by solvent casting method with 2–10 wt % date pit powder. Membrane characterization was done using high pressure gas permeation, X‐ray diffraction, thermogravimetric, and scanning electron microscope analyses. The separation performance and the plasticization resistance property were evaluated in terms of gas permeability, selectivity, and plasticization pressure, respectively. Time dependent performance properties were evaluated up to a pressure of 40 bar for 75 days. Results obtained showed the highest selectivity values of 1.54 (He/H₂), 3.637 (He/N₂), 2.538 (He/CO₂), 2.779 (He/CH₄), 3.179 (H₂/N₂), 3.907 (H₂/CO₂), 1.519 (CH₄/N₂), 1.650 (CO₂/N₂), and 1.261 (CO₂/CH₄) at 10 bar and 35 °C feed pressure and temperature, respectively. The resulting composite membrane showed about 39.50 and 66.94% increase in the selectivity of He/N₂ and CO₂/CH₄, respectively, as compared to the pure polysulfone membrane. Thus, the membrane composites possess some potentials in membrane gas separation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43606.     

The morphology and gas‐separation performance of membranes comprising multiwalled carbon nanotubes/polysulfone–Kapton

The development of desirable chemical structures and properties in nanocomposite membranes involve steps that need to be carefully designed and controlled. This study investigates the effect of adding multiwalled nanotubes (MWNT) on a Kapton–polysulfone composite membrane on the separation of various gas pairs. Data from Fourier transform infrared spectroscopy and scanning electron microscopy confirm that some studies on the Kapton–polysulfone blends are miscible on the molecular level. In fact, the results indicate that the chemical structure of the blend components, the Kapton–polysulfone blend compositions, and the carbon nanotubes play important roles in the transport properties of the resulting membranes. The results of gas permeability tests for the synthesized membranes specify that using a higher percentage of polysulfone (PSF) in blends resulted in membranes with higher ideal selectivity and permeability. Although the addition of nanotubes can increase the permeability of gases, it decreases gas pair selectivity. Furthermore, these outcomes suggest that Kapton–PSF membranes with higher PSF are special candidates for CO₂/CH₄ separation compared to CO₂/N₂ and O₂/N₂ separation. High CH₄, CO₂, N₂, and O₂ permeabilities of 0.35, 6.2, 0.34, and 1.15 bar, respectively, are obtained for the developed Kapton–PSF membranes (25/75%) with the highest percentage of carbon nanotubes (8%), whose values are the highest among all the resultant membranes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43839.     

Gas transport properties of polyaniline membranes

The transport properties of He, H₂, CO₂, O₂, N₂, and CH₄ gases in solvent cast, HCl doped, and undoped polyaniline (PANi) membranes were determined. Measurements were carried out at 40 psi pressure from 19°C to 60°C. An excellent correlation was found between the diffusion coefficients and the molecular diameters of gases. The solubility coefficients of gases were found to correlate with their boiling points or critical temperatures. The sepa-ration factors for CO₂/N₂ and CO₂/CH₄ are dominated by the high solubility of CO₂. These correlations enable us to predict the permeability, diffusion, and solubility coefficients of other gases. After the doping-undoping process, the fluxes of gases with kinetic diameters smaller than 3.5 Å increased but those of larger gases decreased. This results in a higher separation factor for a gas pair involving a small gas molecule and a larger one. © 1996 John Wiley & Sons, Inc.     

Characterization of the permeation properties of CO2N2 gas mixtures in silicone rubber membranes

The separation characteristics of silicone rubber membranes are determined for CO₂N₂ gas mixtures. The analysis is performed as a function of composition, flow rate and pressure of the feed gas. Results are presented in terms of the variation in component permeability and separation factor as a function of the above parameters. Component permeabilities are calculated using the complete mixing model. Data analysis over the studied pressure range shows that the permeability coefficient of pure CO₂ gas in silicone rubber is 15 times higher than that of pure N₂ gas. This behaviour is completely altered for a mixture of the gases, where the calculated separation factors at low feed pressures and low CO₂ mole fractions in the feed stream are two- to three-fold lower than the separation factors for the pure gases. At higher feed pressures and high CO₂ mole fractions in the feed stream, the above behaviour is reversed; the separation factors for the gas mixture are now higher than those for the pure gases. Comparison of the permeation characteristics of silicone rubber and cellulose acetate membranes for CO₂N₂ gas mixtures shows similar ranges and values for the gas permeabilities and separation factors. However, much higher separation factors are obtained for the cellulose acetate membrane in the case of pure gas permeation.     

Investigation of Methane and Carbon Dioxide Gases Permeability Through PEBAX/PEG/ZnO Nanoparticle Mixed Matrix Membrane

This paper presents a new kind of mixed matrix membrane using polyethylene glycol (PEG) as organic filler. In this mix, PEG and ZnO nanoparticles (as inorganic modifier) were added to a PEBAX polymer matrix at different concentration to study their effects on the morphology, permeability and selectivity of the membrane. To characterize the chemical structure of samples FTIR and for morphological characterization, XRD and SEM were employed. The permeability of pure gases CO₂ and CH₄ in PEBAX, and PEBAX/PEG/ZnO with different ZnO and PEG contents were determined by the constant pressure-variable volume method. Also influences of temperature and pressure on permeation properties of these membranes were studied. The results were indicative of an increase in gas permeability and enhancement which for neat PEBAX membrane, CO₂/CH₄ permeability of 44.6 and 2.193 Barrer and selectivity of 20.39 were obtained. The permeability of PEBAX/PEG (40 wt.%)/ZnO (4 wt.%) membrane was enhanced to 94.49 Barrer for CO₂ and 3.933 for CH₄. The selectivity of PEBAX/ZnO(4 wt.%) improved to 31.58 for the CO₂/CH₄ gas pair.     

Gas permselectivity properties of high free volume polymers modified by a low molecular weight additive

The permselectivity properties of mixtures of the highly substituted polymers tetramethylhexafluoro polysulfone (TMHFPSF) and tetramethylhexafluoro bisphenol A t-butyl isophthalate (TMHFBPA-tBIA) with a low molecular weight glassy additive Kenflex A (denoted here as KXA) were measured for different gases and compared with the permselectivity properties shown by the base, unsubstituted polymers polysulfone (PSF) and bisphenol A t-butyl isophthalate (BPA-tBIA). The results show that the selectivity-permeability balance of polymer membranes may be appropriately tailored by a combination of chemical and physical alterations of the base polymer. The addition of modest amounts of KXA (ca. 20 wt %) into TMHFPSF or TMHFBPA-tBIA leads to materials whose permeability/selectivity combination is better than that of the unsubstituted materials, PSF or BPA-tBIA. The polymer TMHFPSF responds more beneficially to the incorporation of KXA than TMHFBPA-tBIA. At the same level of permeability, mixtures based on TMHFPSF have higher selectivity factors for H₂/CH₄ and CO₂/CH₄ than those based on TMHFBPA-tBIA. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 403–415, 1998     

Development and characterization of homopolymers and copolymers from the family of polyphenylene oxides

Poly(2,6‐dimethyl‐1,4‐phenylene oxide), PDMPO, poly(2,6‐diphenyl‐1,4‐phenylene oxide), PDPPO, as well as their copolymers of different compositions, having both random and block structures, have been synthesized and characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and gel permeation chromatography. Solution‐cast films were prepared from all synthesized polymers using chloroform as a solvent. The thermal properties of the resulting films were characterized by differential thermal analysis and differential scanning calorimetry, whereas their morphology was investigated using X‐ray diffraction. Ultimately, the potential of the synthesized polymers for gas separation was studied by examining gas permeation properties of the respective thin films in single gas permeation tests involving N₂, O₂, CH₄, and CO₂. In general, the O₂ and CO₂ permeability coefficients decrease with the PDPPO content. However, the largest drop in the permeability coefficients occurs between PDMPO and a copolymer having the lowest PDPPO content, and the permeability coefficients PDPPO are comparable or even lower than the permeability coefficients of the copolymers having the largest PDDPO content. On the basis of combination of the permeability coefficients and their ratios for CO₂/CH₄ and O₂/N₂, random copolymers appear to be a better candidate for gas separation membranes than their block counterparts. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Gas permeation in miscible blends of poly(methyl methacrylate) with bisphenol chloral polycarbonate

The miscibility of poly(methyl methacrylate) (PMMA) with bisphenol chloral polycarbonate (BCPC) has been studied using differential scanning calorimetry (DSC), optical indication of phase separation on heating (i.e., lower critical solution temperature (LCST) behavior), density measurement, and gas permeation. All evidence indicates that PMMA is miscible with BCPC over the whole blend composition range. Single composition-dependent glass transition temperature and LCST behavior have been observed for each blend. The specific volumes of the blends follow closely the simple additivity rule indicating the interaction between PMMA and BCPC is weak. Gas permeability coefficients for He, H₂, O₂, Ar, N₂, CH₄, and CO₂ measured at 35°C under 1 to 2 atm upstream pressure are lower than those calculated from the semilogarithmic additivity rule. The difference between this calculated permeability and the measured one increases with gas molecular size. As a result, the ideal gas separation factors for He/CH₄, CO₂/CH₄, and O₂/N₂ gas pairs estimated from the ratio of pure gas permeabilities are higher than predicted from the semilogarithmic additivity rule. These permeation results were interpreted in terms of the free volume theory and the activated state theory, which have been proposed to describe gas transport behavior in polymer mixtures.     

Influence of Particle Size on the Performance of Polysulfone Magnetic Membranes for O2/N2 Separation

Magnetic mixed-matrix membranes (MMMs) are fabricated using polysulfone (PSf) and iron oxide (Fe) for O₂/N₂ separation. The effects of Fe nanoparticle size and content on the performance of the membranes are investigated using a novel gas permeation unit in the presence of various magnetic fields. The results indicate that the O₂ permeation is improved by adding Fe nanoparticles into the PSf matrix regardless of the particle size. Furthermore, the selectivity of PSf and PSf-Fe membranes is considerably enhanced by applying a magnetic field during the permeation experiments. The O₂ permeability and O₂/N₂ selectivity of PSf-Fe50 MMMs in the presence of a magnetic field are higher than those of neat PSf membranes.     

Effect of doping treatment on gas transport properties and on separation factors of polyaniline memebranes

Gas permeation experiments of H₂, O₂, CO₂, N₂, and CH₂ were carried out with freestanding films of the conjugated polymer polyaniline (PANi). At first annealed to remove residual solvent, PANi membranes were doped (i.e., protonated) in a strongly acidic medium (HCl 4M), undoped in a basic medium (NH₄OH 1M), and redoped in a slightly acidic medium (HCl 10^?2M). Protonation and deprotonation kinetics were studied by elementary analysis Gas permeation experiments were performed with the annealed, doped, undoped, and redoped PANi films. The gas transport mechanism was clearly influenced by the diffusivity factor and it obeyed a Fickian diffusion model. From the variations in permeability coefficients with the doping treatment, gases could be divided in two subgroups comprising H₂, O₂, and CO₂ on one hand and N₂ and CH₄ on the other. After the doping–undoping–redoping process, gas fluxes were increased by 15% for the smaller gases and were decreased by 45% for the larger gases. As a consequence gas separation factors were approximately doubled for a gas pair involving the two subgroups and these were unchanged for a gas pair involving only one subgroup. The highest O₂/N₂ and CO₂/CH₄ selectivity coefficients were, respectively, equal to 14 and 78. © 1995 John Wiley & Sons, Inc.     

Preparation of composite membranes via interfacial polyfunctional condensation for gas separation applications

Composite membranes were prepared by interfacial polycondensation of a water-soluble diamine (4,4′;-methylene dianiline [MDA] or ethylene diamine [EDA]) with an organic solvent (hexane)-soluble 1,2,4,5-benzenetetra acyl chloride (BTAC) on top of a porous polysulfone (PSF) support. For both the poly(BTAC-MDA) and poly(BTAC-EDA) composite film systems, the permselectivity of these films increases only slightly with an increasing number of coatings. The poly(BTAC-MDA) composite membranes are treated at 135°C in a nitrogen atmosphere for 4 h, and they have a high selectivity [α^*(CO₂/CH₄) = 20.51] and permeability [P?(CO₂) = 44.12 Barrer]. This is due mainly to the great chain stiffness of the formed polyimide, which has high selectivity. The high permeability is due to a porous polysulfone support. The trend of the permeability for this composite film is P?(CO₂) > P?(O₂) > P?(N₂) > P?(CH₄). In poly(BTAC-EDA) composite membranes, the permeation of different gases decreases in the order of P?(CO₂) > P?(O₂) > P?(CH₄) > P?(N₂). As to the composite films being more permeable to CH₄ than to N₂, this is probably due to the presence of a considerable quantity of aliphatic chains (–CH₂–CH₂–) in the poly(BTAC-EDA) composite film caused by its particularly excellent solubility for methane.     

Incorporation of carbon nanofibers into a Matrimid polymer matrix: Effects on the gas permeability and selectivity properties

Composite membranes containing carbon nanofibers (CNFs) and Matrimid were prepared by a solution‐casting method. Prepared Matrimid–CNF composite membranes were characterized with X‐ray diffraction, thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and mechanical testing techniques. The mechanical properties of the composite membranes increased over that of the pristine polymeric membranes. To develop a broad fundamental understanding of the connection between the composite architecture and gas‐transport properties, both the gas‐permeability and gas‐separation characteristics were evaluated. The gas‐transport properties of the Matrimid–CNF composite membrane was measured with a single gas‐permeation setup (He, H₂, N₂, CH₄ and CO₂) at ambient temperature with the variable‐volume method. The incorporation of CNFs (0.5–10 wt %) into the Matrimid matrix resulted in approximately a 22% reduction in the gas permeation of various gases, (H₂, He, CO₂, N₂, and CH₄). Moreover, an improvement of 1.5 times in the gas selectivity was observed for CO₂/CH₄, H₂/CH₄, He/CH₄, and H₂/N₂ compared to pristine polymeric membrane. Hence, such polymer–CNF composite membranes could be suitable for gas‐separation applications with high purity requirements. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46019.