Search

A series of mixed matrix membranes (MMMs) based on polyurethane (PU) and silica nanoparticles was fabricated. Three types of PU were synthesized with different polyethylene glycol (PEG)/polytetramethylene glycol ratios (PU0, PU75, and PU100, the corresponding numbers: PEG percent). The MMMs were characterized using FTIR, SEM, and gas permeation measurements (N2, O2, CH4, and CO2). The phase mixing of PU0 and PU75 membranes increased with silica content. This resulted in a decrease in gas permeability, while an increase in CO2/CH4 and CO2/N2 selectivities. The gas separation trend for PU100 membranes was the opposite. The molecular probing approach was served to study the interfacial structure of the MMMs. The existence of a rigidified polymer layer with 2.38 and 2.44 nm thicknesses around silica was revealed through PU0 and PU75 membranes, respectively. In contrary, silica was surrounded by a polymer chain dilution interphase with a thickness of 2.20 nm for PU100 MMMs. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • New mixed matrix membranes (MMMs) were fabricated. • Dispersion of nanoparticles was controlled by adjusting nanoparticles chemistry. • The gas-separation performance of the MMMs is higher than that of the pristine membrane. Abstract This paper presents a study on control of nanoparticles dispersion in the hard and soft segments of a polyurethane (PU) membrane, via adjusting surface groups of the nanoparticles. The dispersion control allows for tailoring physical and transport properties of the membrane. PU-based mixed-matrix membranes (MMMs) embedded with cyanuric chloride and its derivatives, melamine, and 2,4,6-trihydazino-1,3,5-triazine (THDT) nanoparticles, are prepared. The MMMs are characterized using FTIR, XRD, TGA, DSC, and SEM analyses, and tensile strength tests. Peak assignment of the bonded carbonyl, crystallinity change, mechanical properties of the membranes, possible hydrogen-bonding of the PU backbone and the nanoparticles, and permeation tests indicate that cyanuric chloride nanoparticles are dispersed in the hard segments, whereas melamine and the THDT nanoparticles are distributed in the soft domains. As the cyanuric chloride nanoparticle concentration of the MMMs increases, the gas permeabilities and O 2 /N 2 , CO 2 /CH 4 and CO 2 /N 2 selectivities of the membranes increase. In the case of THDT and melamine, as the filler loading increases, the permeabilities of the gases decrease, whereas O 2 /N 2 , CO 2 /CH 4 and CO 2 /N 2 selectivities increase. A 10 wt% incorporation of THDT into the PU increases CO 2 /N 2 and CO 2 /CH 4 selectivities by 92% and 75%, respectively. These results point to the potential of cyanuric chloride nanoparticles for simultaneous improvement of gas permeability and selectivity, and the potential of melamine and THDT nanoparticles for preparation of highly selective nanocomposite membranes for CO 2 removal. [ABSTRACT FROM AUTHOR]

ABSTRACT: The effect of zeolite 3A, 4A, and ZSM‐5 on the gas separation performance of polyurethane (PU)–zeolite mixed matrix membranes (MMMs) has been investigated in this study. Permeation of pure CO2, CH4, N2, and O2 gases through PU–zeolite MMMs with zeolite content of 6, 12, 18, and 24 wt% was studied. The prepared hybrid membranes were characterized using Fourier transform infrared spectroscopy and scanning electron microscope. Membrane characterization confirmed the homogeneous distribution of zeolite particles at low zeolite loadings in the prepared membranes. The obtained results confirmed a significant enhancement in the permeability of all gases and the CO2/N2, CO2/CH4, and O2/N2 selectivities by increasing the content of zeolite particles in PU–zeolite MMMs. The PU–zeolite 4A with 12 wt% zeolite loading showed the best performance in terms of gas permeability and selectivity for CO2/N2, CO2/CH4 and O2/N2 gas pairs. [ABSTRACT FROM AUTHOR]

The concept of mixed matrix membrane comprising dispersed inorganic fillers into a polymer media has revealed appealing to tune the gas separation performance. In this work, the membranes were prepared by incorporation of mesoporous silica into polyurethane (PU). Mesoporous silica particles with different pore size and structures, MCM‐41, cubic MCM‐48 and SBA‐16, were synthesized by templating method and functionalized with 3‐aminopropyltriethoxysilane (APTES). High porosity and aminated surface of the mesoporous silica enhance the adhesion of the particles to the PU matrix. The SEM and FTIR results showed strong interactions between the particles and the PU chains. Moreover, the thermal stability of the hybrid PUs improved compared to the pure polymer. Gas transport properties of the membranes were measured for pure CO2, CH4, O2, and N2 gases at 10 bar and 25°C. The results showed that the gas permeabilities enhanced with increasing in the loading of modified mesoporous silica particles. High porosity and amine‐functionalized particles render opportunities to enhance the gas diffusivity and solubility through the membranes. The enhanced gas transport properties of the mixed matrix membranes reveal the advantages of mesoporous silica to improve the gas permeability (CO2 permeability up to ~70) without scarifying the gas selectivity (α(CO2/N2)~ 30 for 5 wt% SBA‐16 content). [ABSTRACT FROM AUTHOR]

Poly (ethylene glycol) (PEG)-based polyurethane (PU) membranes are attractive materials for CO 2 separation from various sources such as flue gas and syngas. However, the strong tendency of PEG chains to crystallize leads to reduced permeability of the membrane. Here, we developed new types of PU chemistries with high PEG content and reduced crystallinity. A series of PUs were synthesized based on mixtures of PEG and poly (propylene glycol) (PPG), and various PEG-PPG triblock copolymers (PEG-b-PPG). The presence of PEG-b-PPG triblock copolymers combines the high selectivity of PEG while the PPG pendant methyl group hinders local crystallization. The resulting membranes showed CO 2 permeability of 144 barrer and high CO 2 /N 2 and CO 2 /H 2 selectivities up to 54 and 8.3, respectively. Due to the absence of the crystalline soft phase, synthesized PUs with PEG-b-PPG triblock copolymers exhibit higher chain flexibility which is reflected by a decrease in the glass transition temperature of the soft segments. In contrast, the mixture of PEG and PPG showed minimal effects on the crystallinity of PEG domains. This resulted in lower membrane gas separation performance where CO 2 permeability and CO 2 /H 2 selectivity decreased to 68 barrer and 4.9, respectively. [ABSTRACT FROM AUTHOR]

This study involves the preparation and characterization of polyurethane (PU) and polyurethane/poly(ether-block-amide) (PU/PEBA) blend membranes for gas separation. Polyurethane was synthesized by two-step polymerization based on isophorone diisocyanate (IPDI), polytetramethylene glycol (PTMG2000), 1,4-butanediamine (BDA) and 1,4-butanediol (BDO) in mole ratios of 3:1:2. Two kinds of PEBA, MV3000 and MH1657, were chosen to prepare PU/PEBA blend membranes. The effects of the blend composition on the permeability of N 2 , O 2 , CO 2 and CH 4 were investigated. All membranes were prepared by thermal phase inversion. Physical properties of synthesized polyurethane and prepared blend membranes were investigated by FT-IR, XRD and SEM analyses. FT-IR results indicate that phase separation of hard and soft segments decreased as the amount of PEBA in blend membranes increased. XRD results demonstrate that crystallinity rose by increasing the amount of PEBA in the blends. According to the SEM micrographs of the prepared samples, PU/PEBA blend membranes are miscible systems. The results of gas permeation experiments demonstrate that by increasing the amount of PEBA in PU/PEBA blend membranes, the permeability of all gases decreased while selectivity increased. [ABSTRACT FROM AUTHOR]

In this work, polyurethane (PU) nanocomposite membranes were prepared using different concentrations of alumina (Al 2 O 3 ) nanoparticles (0, 2.5, 5, 10, 20, and 30 wt%). The main objective of this work is to evaluate the permeability of CO 2 , CH 4 , O 2 , and N 2 gases in the polyurethane hybrid membranes at various Al 2 O 3 contents and with two different chain extenders. Polyurethane was synthesized by bulk two-step polymerization based on polytetramethylene glycol (PTMG) and hexamethylene diisocyanate (HMDI). 1,4-butanediol (BDO) and 2-methyl-1,3-propanediol (MPD) were used as chain extenders to complete the conversion of the prepolymers to the final polyurethanes. The prepared polyurethane–Al 2 O 3 membranes were characterized using Fourier Attenuated Total Reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscope (SEM), wide angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC) analyses. The results show a reduction in the gas permeability, but a significant enhancement in the CO 2 /N 2 , CO 2 /CH 4 , and O 2 /N 2 selectivities with alumina content. The separation performances of the membranes were compared with Robeson׳s upper bound limit. The new modified Higuchi model was applied to predict the permeability of polyurethane–alumina hybrid membranes. [ABSTRACT FROM AUTHOR]

In this research, the effects of Zeolite 4Å and ZSM-5 on the separation of C 2 H 6 and C 3 H 8 from CH 4 through polyurethane/zeolite mixed matrix membranes (MMM) are evaluated. Physical properties of synthesized polyurethane and polyurethane/zeolite MMM were investigated by FTIR, XRD, TGA and SEM analyses. Results indicate that phase separation of hard and soft segments in polyurethane would be increased by adding butanediamine (BDA) chain extender in polymer due to the generation of more hydrogen bonds between hard segment domains. The obtained SEM micrographs confirm that the Zeolite is distributed in the polymer matrix homogenously. The results of gas permeation represent that permeability and selectivity of Hydrocarbons are increased by increasing the urea groups in the polymer structure. Moreover, the obtained results of gas permeation of polyurethane–zeolite (4Å) membranes indicate an increase in the permeability of Methane, with the reduction in C 2 H 6 /CH 4 and C 3 H 8 /CH 4 selectivity by increasing the Zeolite 4Å up to 10 wt%. In addition, the results of the gas permeation of polyurethane–zeolite (ZSM-5) MMM indicate a significant increment in permeability and selectivity of all Hydrocarbons. The permeability of Propane and its selectivity over Methane is increased from 64.8 Barrer and 2.6 into 117.2 Barrer and 3.64 in with 20 wt% filled PU–ZSM 5 MMM, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The effect of silica nanoparticles on the gas permeation properties of polycaprolactone-based polyurethane membranes was investigated. Polyurethane and polyurethane-silica nanocomposite membranes were prepared by solution blending and casting-evaporation methods. Silica nanoparticles were prepared by sol–gel method using hydrolysis of tetraethoxysilane (TEOS). Polyurethane was synthesized by bulk two-step polymerization, including polycaprolactone 2000(PCL)/hexamethylene diisocyanate (HMDI)/1,4-butanediol (BDO). The homogeneity and nano scale distribution of the prepared polyurethane-silica membranes were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and thermal gravimetric analysis (TGA). Gas permeation properties of these membranes with different silica contents, was studied for pure CO2, CH4, N2 and O2 gases. The results showed reduction in gas permeability, but enhancement in CO2/N2, CO2/CH4 and O2/N2 ideal selectivity. Also the effect of temperature and pressure on permeation properties of these membranes was investigated. The modified Higuchi model was applied to predict the permeability of polyurethane-silica nanocomposite membranes. Good agreement between the experimental data and the predicted gas permeability was obtained. [Copyright &y& Elsevier]

Abstract: In this study, the effect of the structure of polyether-based polyurethane (PU) membranes on their gas separation properties has been investigated. In this regard, a series of polyurethanes based on hexamethylene diisocyanate (HDI) and 1,4-butanediol as hard segments and different soft segments such as poly(tetramethylene glycol) (PTMG, 2000g/mol), poly(ethylene glycol) (PEG, 2000g/mol) and PTMG/PEG mixture were synthesized. PU membranes were prepared by thermal phase inversion method and their physical properties were analyzed by FT-IR, XRD and DSC analyses. The obtained results from FT-IR and DSC analyses indicated that the phase separation of hard and soft segments decreased and chain mobility was restricted, resulting in the increase in glass-transition temperature of the soft segment, by content of the PEG in the PU structure. The permeability of pure N2, O2, CH4 and CO2 gases were determined using constant pressure method at different feed pressures and temperatures. The results of gas permeation experiments showed that by increasing the ether group content in the polymer structure, permeability of the pure gases decreased, while CO2/N2 ideal selectivity increased. The obtained results also indicated that the permeability of CO2 decrease from 132.52 barrer in PU0 (PU containing 100wt% of PTMG in soft segment) to 20 barrer in PU100 (the PU containing 100wt% of PEG in soft segment), respectively. CO2/N2 selectivity increased from 28 to 90. Trade-off evaluation also showed that the potential of studied membranes for commercialization in CO2/N2 and even CO2/CH4 separations increase by PEG content in polymer and the PU membrane which contains 75/25wt% ratio of PEG/PTMG had the highest. [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: In this study, the effect of silica nanoparticles on the gas permeation properties of polyether-based polyurethane membrane was investigated. Polyether-based polyurethane was synthesized by bulk two-step polymerization of polypropylene glycol/hexamethylenediisocyanate (HMDI)/1,4-butanediol (BDO) in mole ratios of 1:3:2. Silica nanoparticles were prepared through the sol–gel method by hydrolysis of tetraethoxysilane (TEOS). Polyurethane and polyurethane–silica nanocomposite membranes were prepared by solution blending and casting method. The prepared polyurethane–silica membranes were characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), thermal gravimetery analysis (TGA) and differential scanning calorimetry (DSC) analyses. These methods confirmed the homogenous and nano scale distribution of silica nanoparticles in prepared polymers. Gas permeation properties of polyurethane–silica nanocomposite membranes with silica content of 2.5, 5, 10 and 20wt.% was studied for pure CO2, CH4, N2 and O2 gases. The obtained results indicated the reduction in permeability of all gases, but enhancement in CO2/N2, CO2/CH4 and O2/N2 selectivities was observed by increasing the content of non-permeable silica nanoparticles in polyurethane–silica membranes. In the case of polyurethane–silica (20wt.%) nanocomposite membrane, the obtained CO2/N2 selectivity was 1.65 times of pure polyurethane, while the CO2 permeability reduction of polyurethane–silica membranes was 35.6% in comparison with pure polyurethane. Finally, the modified Higuchi model was applied to predict the permeability of polyurethane–silica membranes and fairly good agreement was observed between experimental and predicted gas permeabilities of these membranes. [Copyright &y& Elsevier]

• PUU membranes were designed by different length-side chains based chain extenders. • Shielding hard segment by side chains increased phase separation and reduced FFV. • Dominant plasticizing effect increased permeability by longer side chain based PUU. • The molecular designing of the PUUs allowed a further tuning of gas permeation. Novel poly(urethane-urea) (PUU) membranes were developed as the aim of a structure-property relationship study to enhance gas permeation. Designing the PUUs was followed by three synthesized chain extenders with different length-alkyl side chains, polytetramethylene glycol, and isophorone and hexamethylene diisocyanates. The longest substituted PUU indicated higher phase separation and lower glass transition temperature. Pure and mixed gas permeabilities of prepared membranes grew as phase separation of PUU material increased, while fractional free volume decreased by lengthening the side chain of the PUUs. The reasons for this event were the migration of the side chains to the surface of hard domain, thereby shielding it and filling the soft/hard interface. Enhanced permeability of materials with l onger side chains is attributed to its plasticizing effect. The highest CO 2 permeability (287 barrer) was obtained for the longest substituted PUU. The findings revealed an increase in gas permeation without a significant reduction of selectivity by longer substituted PUUs. [ABSTRACT FROM AUTHOR]

Polyurethanes (PUs) and polyurethane-ureas (PUUs), with good mechanical stability and the possibility of tuning the gas transport properties are promising materials for selective gas separation membranes. Here, we synthesized various types of PUs and PUUs with polytetramethylene glycol (PTMG), isophorone diisocyanate (IPDI) and different ethereal chain extenders (1:3:2 M ratio). FTIR and DSC results showed that the phase separation would vary in PUs and PUUs structures by changing the length and functionality of the chain extenders. More mixing was inferred for PUs and PUUs with high ethereal content. In contrast, phase separation was more likely with increases in the chain extender length. Pure (CO 2 , CH 4 , O 2 and N 2 ) and mixed gas (CO 2 :N 2 (50:50 vol%) and CO 2 :CH 4 (50:50 vol%)) permeation measurements correlated well with the phase separation in the polymer structure. The octanediamine-based PUU with the highest amount of phase separation showed the highest permeability (160 barrer for CO 2 and CO 2 /N 2 selectivity of 30). On the other hand, the 3,6-dioxa- 1,8-octanediol- based PU, despite having the same chain extender length as octanediamine-based PUU, presented the lowest phase separation and gas permeability (62 barrer for CO 2 and CO 2 /N 2 selectivity of 29). [ABSTRACT FROM AUTHOR]