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In this study, the effect of solvent type and nanoparticles of silica and zeolite 4A on the gas separation properties of polyimide (PI) membranes were investigated. Gas separation of the membranes based on pure solvents of dimethylformamide (DMF), n‐methyl‐2‐pirrolidone (NMP), dimethylacetamide (DMAc), and dimethylsulfoxide (DMSO) were studied. The prepared PI membranes using DMAc and DMSO showed the highest selectivity and permeability, respectively. In this regard, the influence of their mixing on transport properties of the PI was evaluated. The prepared membrane using the mixture of DMSO/DMAc with the volume ratio of 1:3 showed the best gas separation performance in comparison to the Robeson's upper bound. Incorporation of 20 wt% of silica and zeolite 4A nanoparticles into the PI membrane indicated that the selectivity of CO2/CH4 increased from 39.4 to 57.6 and 68.5, respectively. Besides, gas transport properties of the PI‐based mixed matrix membranes were satisfactory predicted by modified Maxwell model. Furthermore, characteristic parameters of the encapsulated particles by interfacial layer were determined. [ABSTRACT FROM AUTHOR]

In this research, the effect of polyethylene glycol (PEG) molecular weight on permeability and selectivity of polysulfone/polyethylene glycol (PSF/PEG) composite membrane is investigated. Polyethylene glycol with molecular weights of 4000, 6000, and 10,000 is applied. It is shown from the results that PEG applied in composite membranes with molecular weight of 1000 had the best diffusivity in comparison with the other composite membranes containing PEG with lower molecular weights. In addition, it is perceived that the permeability of CO2 from PSF/PEG10000 composite membranes has increased with enhancing weight percent. CO2 permeability into PSF/PEG composite membranes containing 20 wt% PEG10000 is calculated 7.64 barrer (1 barrer = 10−10 cm3 (STP) cm/cm2 s cmHg). The ideal selectivity for CO2/N2 gas pair in PSF pure membrane and composite membranes containing 10 wt% and 20 wt% PEG10000 are calculated 26.57, 30.61, and 32.12, respectively. Finally, the morphology and membrane structure of the membrane were evaluated with infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile strength test. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the effects of silica nanoparticles on the permeability of pure CO2, O2, and N2 gases in cellulose acetate (CA) membrane have been studied. Silica particles were prepared via the sol–gel method through the hydrolysis of tetraethyl orthosilicate (TEOS). CA and CA/silica nanocomposite membranes were prepared by thermal phase inversion method. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Fourier transfer infrared (FTIR) analyses were employed to characterize the CA and CA/silica nanocomposite membranes. Gas permeation experiments showed an increase in the permeability of CO2 from 6.32 to 7.3 barrer and a reduction in the permeability of N2 from 0.18 to 0.09 barrer with the increment in silica content of the prepared composite membranes up to 20 wt%. Therefore, CO2/N2 selectivity of the nanocomposite membranes increased by increasing the silica content in the polymer matrix from 30 to 80 for 20 wt% load of silica. [ABSTRACT FROM AUTHOR]

A new model for prediction of the effective permeability of gases in mixed matrix membranes (MMMs), considering the effects of particle shape and the interfacial layer, is presented. The proposed model treats core filler particles and interfacial shell layers as complex particles. Moreover, the Bruggman mathematical procedure is used to improve the accuracy of the presented model for high concentrations of fillers in MMMs. Also, an appropriate uniform criterion is established to make efficient use of the new model for various experimental data to avoid the need for curve-fitting procedures. Finally, the proposed model is examined for several sets of experimental data. [ABSTRACT FROM AUTHOR]

Abstract: In this research, the effects of changing the polyol, disocyanate, and chain extender used in synthesized polyurethane membranes on gas permeability are investigated. The membranes are synthesized using PTMG, PPG, PCL as polyol; IPDI, HDI, TDI as diisocyanate; and BDO, BDA as chain extender in a 1/3/2 and 1/2/1M ratio of polyol/diisocyanate/chain extender. The results obtained from Fourier transfer infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) confirmed that changing the polyol type from PPG to PTMG and PCL leads to more phase interaction. Furthermore, changing the diisocyanate group from aromatic to aliphatic and from cyclic aliphatic to linear aliphatic leads to an increase in phase separation of hard and soft segments which cause the packing density of hard segment due to the enhancement of the hydrogen bonding. In addition, changing a chain extender from a diol one to a diamine leads to an increase in phase separation of hard and soft segments. Permeation experiments reveal that the larger, more condensable gases are more permeable than light ones in more rubbery polymers; and, the selectivity of polyurethane as a rubbery polymer is dominated by solubility. On the other hand, by enhancement of the microphase separation of hard and soft segments, the rubbery behavior and permeability of condensable gases increase along with their selectivity. Overall, polymers based on the PPG polyol show maximum permeability because of their higher rubbery property due to its higher phase separation. The results of permeability tests indicate high permeability, up to 200Barrer (1Barrer=1×10−10 [cm3 (STP) cm/cm2 scmHg]), and high selectivity for propane with respect to methane (C3H8/CH4: 5.47). [Copyright &y& Elsevier]

Abstract: This work presents the structural properties of gas permeation of a group of polyurethane membranes. All polymers were synthesized using a 1:3:2 molar ratio of polyol:diisocyanate:chain extender. The obtained results from Fourier transform infrared spectrometer (FT-IR) of polymers indicate that by changing the diisocyanate from aromatic to linear aliphatic, the microphase separation of hard and soft segments increases. Study of the differential scanning calorimetery (DSC) and X-ray diffraction (WAXD) patterns confirmed that PTMG and PCL polyols can be arranged in small crystalline structures. Furthermore, a hard ordered segment in crystal phase could be obtained, owing to the high phase separation of the polymer based on HDI. Permeation measurements of polymers revealed that the permeability of gases increases with microphase separation in polymer and selectivity of gases drops down. Polymers based on PPG showed the highest phase separation and permeability. The obtained results revealed more phase mixing of the polymer based on DMPA chain extender in comparison to BDO, which lead to lower permeability and higher selectivity. The solubility and diffusivity of gases indicate solubility domination of gas transport in these membranes. The observed solubility domination increases by phase separation. The results of permeability tests indicate high permeability, up to 186Barrer (1Barrer=1×10−10 [cm3 (STP) cm/cm2 scmHg]), and high selectivity for carbon dioxide with respect to nitrogen (CO2/N2: 45). Our data sheds light on gas permeation properties of polyurethane membranes. [Copyright &y& Elsevier]

Abstract: The effect of urethane and urea contents on gas separation properties of the groups of polyurethane–urea membranes is studied. The membranes used in this study were prepared by polytetramethylene-glycol (PTMG) and isophorone diisocyanate (IPDI) prepolymers. The prepolymers were converted to final polymer using the designed proportion of 1,4-butane diol (BDO) and 1,4-butane diamine (BDA) as a chain extender. Five different BDO/BDA ratios were chosen in order to synthesize poly(urethane-urea)s with different urethane/urea linkage content. The prepared polymers were characterized and the permeability of gases through them was investigated. Results obtained by Fourier transform infrared spectrometer (FT-IR) and differential scanning calorimetery (DSC) indicate that by increasing the urea linkage in the polymers, the microphase separation of hard and soft segments increase. Study of the X-ray diffraction (WAXD) patterns confirmed that polyols may be arranged in small crystalline structures. Permeation measurements of polymers revealed that the permeability of gases decreases with increasing urethane content in the polymers and selectivity of gases decreases with increasing urea content. The solubility and diffusivity of gases indicate solubility domination of gas transport in these membranes. The results of permeability also show high amounts up to 128Barrer (1Barrer=1×10−10 [cm3 (STP) cm/cm2 scmHg]), and high selectivity for carbon dioxide with respect to nitrogen (CO2/N2: 27). [Copyright &y& Elsevier]

Abstract: In the present work, the effect of silica nano particles on the permeability of CO2, CH4 and N2 gases in polybenzimidazole (PBI) membranes has been studied. Silica particles were prepared via the sol–gel method through the hydrolysis of tetraethoxysilane (TEOS). PBI and PBI–silica hybrid membranes were prepared by thermal phase inversion method. Scanning electron microscopy (SEM), X-ray diffraction and FTIR analyses were employed in order to characterize the PBI and PBI–silica composite membranes. The obtained SEM micrographs confirmed the nano-scale distribution of silica particles in the polymer matrix. Gas permeation experiments showed an increase in the solubility and a corresponding reduction in the diffusivity of the gases through the membranes by increasing the silica content in the polymer matrix; consequently, the permeability of the condensable CO2 and CH4 gases were enhanced whereas that of non-condensable N2 gas significantly decreased upon increasing the silica content of the nano-composite membranes. The permeability of CO2 and its selectivity over N2 was increased from 0.025Barrer and 3.5 in pure PBI to 0.11Barrer and 71.3 in the nano-composite containing 20wt% of the silica particles. There was a strong correlation between the solubility coefficients and condensability of the gases, as well as the diffusion coefficient of the penetrants and their kinetic diameter. Higuchi model fitted fairly well with the experimental results concerning the permeability of nitrogen gas in nanocomposite membranes, supposing the K H =3.8. [Copyright &y& Elsevier]

Poly(ether sulfone) (PES), because of its low chain mobility and high gas selectivity, was selected as a gas‐separation membrane. Because poly(ethylene glycol) (PEG) contains polar ether groups favorable for carbon dioxide (CO2) capture, we investigated the effects of PEG on the CO2/CH4 and CO2/N2 separation properties of PES–PEG blend membranes. PEG with different molecular weights (4000, 6000, and 10,000) and concentrations of up 30 wt % was added to PES. Scanning electron microscopy and wide‐angle X‐ray diffraction analyses on the blends confirmed the uniformity and dense surfaces of the membranes and no changes in the crystallinity, respectively. Fourier transform infrared spectra indicated good interactions between the PEG and PES segments. Gas permeation tests showed that with increasing PEG molecular weight, its weight fraction permeability of CH4 and CO2 increased, whereas the permeability of O2 and N2 decreased. The best composition of PES–PEG was a 70/30 ratio; with this composition, the selectivities of CO2/N2 and CO2/CH4 were enhanced by 64 and 14%, respectively, compared to that of the pure membrane. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46845. [ABSTRACT FROM AUTHOR]

• A modified form of Van't Hoff-Arrhenius model was developed. • The model considers the effects of temperature and pressure on transport properties of polymeric and MMMs. • This model is able to consider pressure dependency of E p , E d , Δ H s , P o , S o and D o. • The validity of the model was confirmed by our experiments and the literature data. • The validation of model confirms 95% accuracy of the proposed model. Due to the temperature and pressure dependency of gas transport through polymeric and mixed matrix membranes, probing of their separation performance at different operational conditions seems crucial to determine an optimal operational condition. To minimize the number of costly and time consuming experiments, a modified form of van't Hoff-Arrhenius model was developed to consider the simultaneous effects of temperature and pressure on the separation performance of polymeric and mixed matrix membranes. Moreover, the proposed model is capable to consider pressure dependency of energetic parameters of Arrhenius model including activation energies of permeability and diffusivity, heat of sorption and the corresponding pre-exponential factors. The validity of the proposed model was investigated by using permeation coefficients of CO 2 and N 2 in a binary mixture through 6FDA-DAM at different temperatures in the range of 35–55 °C and in the feed pressure range from 2 to 5 atm. Besides, from data taken from the literature, the proposed model was validated by the prediction of temperature and pressure dependency of transport properties of glassy and rubbery polymers as well as mixed matrix membranes (MMMs) for different gas molecules including He, H 2 , CO 2 , O 2 , N 2 , CH 4 and C 4 H 10. Predictions corresponding to 300 data points revealed that the maximum average absolute relative error was 5.1%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Developing an algorithm for optimization of characteristic parameters in MMMs. • Maximum interphase thickness is determined by the size and loading of particles. • Decreasing the sensitivity of predictive models to the number of experimental data. • Absence of arbitrary assumptions for adjustable parameters. In this study, a new algorithm was developed to mathematically insight into the interfacial morphology in mixed matrix membranes (MMMs) by only using related experimental permeation data to a maximum loading of particles used in MMM preparation. According to this algorithm, the maximum possible interphase thickness is determined based on the size and the maximum used loading of particles in membrane fabrication. The benefits of this approach are determining the optimal characteristic parameters of the surrounded particles including interphase thickness, effective permeability of interphase, and porous particles (if applicable) affected by the blockage, with no arbitrary assumption to them. The validity of the proposed modeling approach was evaluated using 154 data points related to experimental permeability data of 13 series MMMs. Comparing the results obtained by using related experimental data to maximum used particle loading and all loading levels revealed that the sensitivity of the modified Maxwell model to the number of applied experimental data points is negligible. The predictions indicate that the maximum average absolute relative error (AARE) is 9%. Using modified GPG and modified Higuchi models instead of the modified Maxwell model in the proposed modeling approach showed that this algorithm is not sensitive to the type of model. [ABSTRACT FROM AUTHOR]

In this study, a new method was developed for the characterization of the interface morphology in polymer/particle composites. This method, not limited to a specific polymer or particle, utilizes the gas permeability of the composites to determine the interfacial properties such as the type of polymer-particle interactions as well as the thickness and the transport properties of the interphase. Moreover, it can be employed to determine the size of the aggregates in the case of particle aggregation. The proposed method was evaluated by comparing its results with the findings of the small-angle X-ray scattering (SAXS) analysis for polyethersulfone (PES)-based composites containing pristine and fumed silica nanoparticles. Our method was also evaluated by analyzing the results of other studies obtained from the literature. Image 1 • A new method was developed to characterize unknown nature of interphase in polymer/particle composites. • Thickness and permeation of interphase are specified by molecular probing. • The method determines dispersion state of particles and the size of aggregates. • SAXS analysis confirmed the obtained results by the proposed method. • This method not limited to a specific polymer or particle. [ABSTRACT FROM AUTHOR]