The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
William J Koros - One of the best experts on this subject based on the ideXlab platform.
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a high performance hydroxyl functionalized polymer of intrinsic microporosity for an environmentally attractive membrane based approach to decontamination of sour natural gas
Journal of Materials Chemistry, 2015Co-Authors: Ingo Pinnau, William J KorosAbstract:Acid gases carbon dioxide (CO2) and hydrogen sulfide (H2S) are important and highly undesirable contaminants in natural gas, and membrane-based removal of these contaminants is environmentally attractive. Although removal of CO2 from natural gas using membranes is well established in industry, there is limited research on H2S removal, mainly due to its toxic nature. In actual field operations, wellhead pressures can exceed 50 bar with H2S concentrations up to 20%. Membrane plasticization and competitive mixed-gas sorption, which can both lead to a loss of separation efficiency, are likely to occur under these aggressive feed conditions, and this is almost always accompanied by a significant decrease in membrane selectivity. In this paper, permeation and separation properties of a hydroxyl-functionalized polymer with intrinsic microporosity (PIM-6FDA-OH) are reported for mixed-gas feeds containing CO2, H2S or the combined pair with CH4. The pure-gas permeation results show no H2S-induced plasticization of the PIM-6FDA-OH film in a pure H2S feed at 35 °C up to 4.5 bar, and revealed only a slight plasticization up to 8 bar of pure H2S. The hydroxyl-functionalized PIM membrane exhibited a significant pure-gas CO2 plasticization resistance up to 28 bar feed pressure. Mixed-gas (15% H2S/15% CO2/70% CH4) permeation results showed that the hydroxyl-functionalized PIM membrane maintained excellent separation performance even under exceedingly challenging feed conditions. The CO2 and H2S permeability isotherms indicated minimal CO2-induced plasticization; however, H2S-induced plasticization effects were evident at the highest mixed gas feed pressure of 48 bar. Under this extremely aggressive mixed gas feed, the binary CO2/CH4 and H2S/CH4 permselectivities, and the combined CO2 and H2S acid gas selectivity were 25, 30 and 55, respectively. Our results indicate that OH-functionalized PIM materials are very promising candidate membrane materials for simultaneous removal of CO2 and H2S from aggressive natural gas feeds, which makes membrane-based gas separation technology an attractive option for clean energy production and reducing greenhouse gas emissions.
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chemically cross linkable polyimide membranes for improved transport plasticization resistance for natural gas separation
Polymer, 2015Co-Authors: Hiroshi Eguchi, Danny J Kim, William J KorosAbstract:Abstract A series of cross-linkable membrane materials based on the 6FDA-DAM:DABA (3:2) polyimide with enhanced transport plasticization resistance were synthesized to separate CO 2 from CH 4 . Glycidol was used as a cross-linking agent to modify 6FDA-DAM:DABA (3:2) efficiently and form a transesterification reaction-based cross-linking. The conversion was calculated by solution 1 H NMR. These materials were also characterized via density, glass transition temperature, permeation, and sorption measurements. Pure (CO 2 , CH 4 ) and mixed gas (CO 2 /CH 4 ) permeation was studied on dense films of these materials up to 700 psia (1000 psia) for pure CO 2 (50%:50% CO 2 :CH 4 mixed gas) feed. Compared to the 6FDA-DAM:DABA (3:2) membrane, CO 2 -induced plasticization resistance for cross-linked membranes was enhanced in aggressive feed streams. Under CO 2 feed conditions at 35 °C, plasticization for the 41% glycidol-modified cross-linked membrane was not observed up to approximately 450 psia. Glycidol-induced cross-linking offers an excellent balance of selectivity, permeability, and plasticization resistance. The glycidol-modified 6FDA-DAM:DABA (3:2) is competitive with the earlier reported 1,3-propanediol modified materials. Possible issues such as resistance to contaminants may be final determinants in choice of approach; however, this topic was beyond the scope of the current study.
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gas separation performance of 6fda based polyimides with different chemical structures
Polymer, 2013Co-Authors: Wulin Qiu, Donald R Paul, Chienchiang Chen, William J KorosAbstract:Abstract 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 CO 2 and CH 4 transport and plasticization stability of the polyimides membranes relevant to natural gas purification. The consideration of the other gases (He, O 2 and N 2 ) 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 CO 2 plasticization responses for the un-cross-linked polyimides showed good plasticization resistance to CO 2 /CH 4 mixed gas with 10% CO 2 ; however, only the cross-linked polyimides showed good plasticization resistance under aggressive gas feed conditions (CO 2 /CH 4 mixed gas with 50% CO 2 or pure CO 2 ). For future work, asymmetric hollow fibers and carbon molecular sieve membranes based on the most attractive members of the family will be considered.
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cross linkable polyimide membrane for natural gas purification and carbon dioxide plasticization reduction
Macromolecules, 2007Co-Authors: Alexis M W Hillock, William J KorosAbstract:The ability of propanediol monoester cross-linkable (PDMC) polymer to effectively separate CO2 from CH4, and the polymer's stability against plasticization under high CO2 pressures, was investigated. The cross-linked PDMC membranes were found to have significantly higher CO2 permeability and slightly higher selectivity for the CO2/CH4 separation than the un-cross-linked PDMC membranes. Cross-linking temperature was found to have a significant impact on the permeation properties of the membranes. The PDMC membrane permeation results are compared with previous research that uses other cross-linking agents for CO2 plasticization resistance and found to offer an excellent balance between extent of cross-linking and tradeoff between mechanical and transport properties. The cross-linked membranes not only outperform the un-cross-linked membranes with their enhanced transport properties but also provide vastly superior plasticization resistance against aggressive CO2 steams. Un-cross-linked and cross-linked PDMC...
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the effects of crosslinking chemistry on co2 plasticization of polyimide gas separation membranes
Industrial & Engineering Chemistry Research, 2002Co-Authors: John D Wind, Donald R Paul, Claudia Staudtbickel, William J KorosAbstract:To suppress undesirable plasticization effects in CO2/CH4 separations, crosslinkable 6FDA-based copolyimides were synthesized by using 3,5-diaminobenzoic acid (DABA) as one of two diamine monomers. DABA contains a carboxylic acid group that can be used to crosslink the polymer chains with ethylene glycol and aluminum acetylacetonate. These chemistries were compared for effectiveness in suppressing CO2 plasticization on the basis of pure CO2 permeation and sorption data up to 800 psia. The time and pressure dependencies of permeation and sorption were analyzed to characterize the plasticization phenomenon and how it can be controlled by covalent crosslinking. Mixed-gas permeation data are reported up to a total feed pressure of 850 psia for the separation of 50:50 CO2/CH4 mixtures at 35 °C. Selectivity losses with increasing feed pressure are modeled to further understand the effects of plasticization, dual-mode sorption, gas-phase nonidealities, and bulk flow on membrane performance. Additionally, a short...
Matthias Wessling - One of the best experts on this subject based on the ideXlab platform.
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Materials dependence of mixed gas plasticization behavior in asymmetric membranes
Journal of Membrane Science, 2007Co-Authors: Tymen Visser, N. Masetto, Matthias WesslingAbstract:The mass transport of asymmetric membranes for the separation of carbon dioxide/methane mixtures is determined by competitive sorption and plasticization. With increasing feed pressure in mixed gas experiments, the selectivity decreases due to both effects. Distinction whether one or the other mechanism is responsible for the selectivity loss is important since competitive sorption is related to intrinsic material properties and cannot be tailored, whereas plasticization can be suppressed by various chemical means. This paper describes the systematic analysis for five different asymmetric membranes with respect to the balance between competitive sorption and plasticization. Four asymmetric membranes where prepared for this study, one membrane was based on a commercial precursor. Of these membranes, three are based on the polyimide Matrimid: pure Matrimid, and blends of Matrimid with polyethersulfone as well as Matrimid with a polyimide P84. These membranes are compared with two other ones: cellulose acetate and polyphenyleneoxide PPO. The blend of Matrimid with P84 shows the highest mixed gas selectivity and is very resistant against plasticization without any further chemical modification.
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on the subtle balance between competitive sorption and plasticization effects in asymmetric hollow fiber gas separation membranes
Journal of Membrane Science, 2005Co-Authors: Tymen Visser, G H Koops, Matthias WesslingAbstract:The paper describes the influence of a varying feed composition of CO2/CH4 and CO2/N2 mixtures on the gas separation performance of integrally skinned asymmetric PES/PI hollow fibers with an effective skin thickness of 0.27 ?m. Normally, thin membrane structures (<3 ?m) show accelerated plasticization behavior induced by CO2 in pure gas measurements. This study shows that introducing an inert gas to the CO2 feed mixture apparently suppresses plasticization. This effect is more pronounced at higher concentrations of inert gas, supported by a continuous drop in CO2 permeance as a function of CO2 fugacity. At a concentration of 80% inert gas in the feed mixture, the CO2 permeance reduces more than 35% from its initial value, whereas the reduction is 8?10% with 2% inert gas in the feed mixture. However, a mixed gas permeation model predicts for all experimentally used gas compositions similar decreases in CO2 permeance. Plasticization effects seem to be counterbalanced by competitive sorption. This effect becomes larger with increasing inert gas concentration. At 80% inert gas plasticization effects appear to be completely counterbalanced by competitive sorption. Besides that, for all gas compositions, the separation factor decreases with increasing feed pressure, generally assumed as an indication of plasticization. However, such a selectivity decrease is also predicted by the dual mode sorption model, which neglects effects of plasticization. More pronounced indication of plasticization effects is observed when the N2 permeance decay is followed in time after the membrane has been in contact with CO2 at elevated CO2 partial pressures. A significant enhanced N2 permeance is observed due to polymer network dilation, which decreases very slowly in time. There seems to be a subtle balance between plasticization and competitive sorption during mixed gas experiments with integrally skinned asymmetric hollow fibers, which results in the observed phenomenon.
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Accelerated plasticization of thin-film composite membranes used in gas separation
Separation and Purification Technology, 2001Co-Authors: Matthias Wessling, M. Lidon Lopez, H. StrathmannAbstract:Permeation experiments with He, N2, O2 and CO2, have been carried out with double layer composite membranes consisting of a silicone rubber support layer and a thin polyimide layer determining the permeation properties. The estimated thickness of the polyimide layer in the composite membranes was between 1.5 and 4 microns. This paper describes the phenomenon of accelerated plasticization of such thin polyimide layers used in gas separation membranes. The pressure-normalized fluxes were determined at 5 bars for N2, O2 and in the range of 1?8 bars in the case of He and CO2. Helium permeation decreased with increasing feed pressure and no hysteresis behavior was found for successive increasing and decreasing feed pressure steps. For CO2, the pressure-normalized flux did not follow the typical behavior of glassy polymers but increased continuously with increasing feed pressure. Also, CO2 permeation showed a clear hysteresis effects resulting in an increasing permeability with time and an elevated magnitude in successive decreasing feed pressure steps. Hence, stronger plasticization effects in the composite membranes must be concluded in comparison with thick single film membranes. The plasticization effects are significantly pronounced as the polyimide concentration in the solution from which the membranes are cast become more dilute. The latter is interpreted as accelerated plasticization with decreasing film thickness.
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suppression of gas separation membrane plasticization by homogeneous polymer blending
Aiche Journal, 2001Co-Authors: A Bos, H. Strathmann, Ineke G M Punt, Matthias WesslingAbstract:Plasticization is a phenomenon frequently encountered in the application of glassy polymeric materials for solution-diffusion membranes. Conventional methods for stabilizing the membrane are either annealing or cross-linking, which hardly influence the selectivity of the membrane, but decrease the permeability. For single-gas experiments, the literature shows that plasticization can be stabilized by blending a polymer with high plasticization tendencies with one that is hardly affected by the sorbed molecules. Most permeation experiments are carried out with pure CO2, but little is known about the transport properties determined from mixed gas experiments. Stabilization of plasticization in mixed-gas experiments for polymer blends of the polyimide Matrimid and polysulfone is reported, as well as transport properties of a new homogeneous polymer blend based on Matrimid and the copolyimide P84. Experimental results show that the material is stabilized against carbon dioxide plasticization and selectivity for a carbon dioxide/methane mixture significantly improves.
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co2 induced plasticization phenomena in glassy polymers
Journal of Membrane Science, 1999Co-Authors: A Bos, Matthias Wessling, Ineke G M Punt, H. StrathmannAbstract:A typical effect of plasticization of glassy polymers in gas permeation is a minimum in the relationship between the permeability and the feed pressure. The pressure corresponding to the minimum is called the plasticization pressure. Plasticization phenomena significantly effect the membrane performance in, for example, CO2/CH4 separation processes. The polymer swells upon sorption of CO2 accelerating the permeation of CH4. As a consequence, the polymer membrane loses its selectivity. Fundamental understanding of the phenomenon is necessary to develop new concepts to prevent it. In this paper, CO2-induced plasticization phenomena in 11 different glassy polymers are investigated by single gas permeation and sorption experiments. The main objective was to search for relationships between the plasticization pressure and the chemical structure or the physical properties of the polymer. No relationships were found with respect to the glass-transition temperature or fractional free volume. Furthermore, it was thought that polar groups of the polymer increase the tendency of a polymer to be plasticized because they may have dipolar interactions with the polarizable carbon dioxide molecules. But, no dependence of the plasticization pressure on the carbonyl or sulfone density of the polymers considered was observed. Instead, it was found that the polymers studied plasticized at the same critical CO2 concentration of 36±7 cm3 (STP)/cm3 polymer. Depending on the polymer, different pressures (the plasticization pressures) are required to reach the critical concentration.
Sandra E Kentish - One of the best experts on this subject based on the ideXlab platform.
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the impact of toluene and xylene on the performance of cellulose triacetate membranes for natural gas sweetening
Journal of Membrane Science, 2018Co-Authors: Liang Liu, Colin A Scholes, Shinji Kanehashi, Sandra E KentishAbstract:Abstract The presence of condensable aromatic hydrocarbons in raw natural gas streams creates a significant challenge for acid gas removal through membrane separation. In this work, the impact of toluene and xylene on the gas separation performance of cellulose triacetate (CTA) membranes was studied. When operating at low CO2 partial pressures (0.75 bar), both toluene and xylene reduced the permeation of CO2 at low vapour activities, due to competitive sorption and the pore-filling or anti-Plasticisation effect. Conversely, at vapour activities greater than 0.5, toluene caused membrane Plasticisation, possibly coupled with a decrease in crystallinity. On the other hand, when operating at 7.5 bar CO2 pressure, Plasticisation was observed at a lower vapour activity of 0.3 for both toluene and xylene. This study shows that two penetrants can influence the Plasticisation behaviour in a co-operative manner that cannot be described by a simple additive model. The study also shows that the permeabilities of toluene and xylene are comparable with that of methane.
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plasticization of ultra thin polysulfone membranes by carbon dioxide
Journal of Membrane Science, 2010Co-Authors: Colin A Scholes, George Q Chen, Geoff W Stevens, Sandra E KentishAbstract:Abstract Plasticization of gas separation membranes by carbon dioxide permanently alters their performance and increases the possibility of membrane failure. This is amplified in ultra-thin composite membranes, where the active polymeric layer is less than 2 μm. Here, the plasticization influence of CO 2 is measured on ultra-thin polysulfone composite membranes for a range of active layer thicknesses, at four temperatures. The resulting permeability–pressure isotherms demonstrate plasticization occurs for all thicknesses at pressures lower than has been reported for dense membranes. These isotherms were quantitatively fitted with an expanded dual-sorption model that takes into account plasticization of the membrane. The plasticization potential of CO 2 for polysulfone was found to increase with reduced active layer thickness. Similarly, the plasticization potential of CO 2 was found to decrease with temperature. These results are consistent with similar research that shows that thin films behave differently to dense membranes.
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effects of carbon dioxide induced plasticization on the gas transport properties of glassy polyimide membranes
Journal of Membrane Science, 2007Co-Authors: Shinji Kanehashi, Sandra E Kentish, Tsutomu Nakagawa, Kazukiyo Nagai, Xavier J Duthie, Geoff W StevensAbstract:Abstract The time dependence of carbon dioxide (CO 2 ) transport properties, such as permeability, solubility, and diffusivity, in glassy polyimide membranes was investigated in terms of membrane preparation protocols ( i.e. , casting solvent and thermal treatment). The polyimide used was 6FDA-TeMPD (4,4-(hexafluoroisopropylidene) diphthalic anhydride) (6FDA)-2,3,5,6-tetramethyl-1,4-phenylene-diamine (TeMPD). The time dependence of CO 2 permeability in the as-cast 6FDA-TeMPD membranes prepared from tetrahydrofuran and dichloromethane showed typical CO 2 -induced plasticization at pressures over 10 atm. The critical plasticization pressure at which CO 2 -induced plasticization begins to affect the gas permeability shifted from nearly 10–30 atm after heat treatment. The increase in CO 2 permeability upon plasticization is mostly caused by an increase in CO 2 diffusivity. Furthermore, we found that regardless of the membrane preparation protocol, there is a critical CO 2 diffusivity of 73 ± 5 × 10 −8 cm 2 /s at the plasticization pressure in 6FDA-TeMPD membranes.
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operating temperature effects on the plasticization of polyimide gas separation membranes
Journal of Membrane Science, 2007Co-Authors: Xavier J Duthie, Sandra E Kentish, Kazukiyo Nagai, Clem E Powell, Greg G Qiao, Geoff W StevensAbstract:Abstract Membrane plasticization is the process whereby penetrant dissolution causes membrane swelling or dilation, which in turn, can increase membrane diffusivity and solubility and lead to long time frame polymer relaxation processes. In this work, the effect of temperature upon the plasticization of a rigid polyimide, poly(4,4′-hexafluoroisopropylidene diphthalic anhydride–2,3,5,6-tetramethyl-1,4-phenylenediamine) (6FDA-TMPDA), by carbon dioxide is investigated. It is found that across the full range of temperatures studied, plasticization has little effect on carbon dioxide solubility as all results can be characterized by a standard dual mode sorption model. However, the effect upon diffusivity is significant and this can be described by both an exponential relationship with penetrant concentration and an Arrhenius relationship with temperature. The polymer relaxation processes induced by plasticization are also temperature dependent. However, the total proportion of penetrant sorption associated with such relaxation processes is relatively unaffected by temperature. This paper shows that plasticization effects are dominated by Henry's law dissolution. Conversely, while Henry's law species contribute most to diffusion at high temperatures, at lower temperatures the movement of Langmuir component species also contributes to the total diffusion coefficient.
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Thermal dependence of carbon dioxide transport through a dense polymeric membrane
Greenhouse Gas Control Technologies 7, 2005Co-Authors: Xavier J Duthie, Sandra E Kentish, Kazukiyo Nagai, Clem E Powell, Geoffrey W. StevensAbstract:Publisher Summary Polymeric gas separation membranes are currently used commercially for CO2/CH4 separation in a number of operations worldwide. However, a major technical hurdle associated with such membranes is the plasticization of the membrane with increasing concentrations of polar gases such as CO2. Significant research efforts are being conducted into characterizing and avoiding the plasticization phenomena. This chapter presents a study that investigates the permeability of polyimide membranes formed from a readily available commercial membrane Matrimid 5218 in carbon dioxide at temperatures up to 100°C and pressures up to 2500kPa. In this study, membranes were tested in both as cast and thermally annealed formats. The effect of thermal annealing on plasticization has also been examined. Thermal annealing was found to suppress plasticization of the membranes in this temperature and pressure range. It was shown that some degree of crosslinking occurred during annealing, leading to a reduction of carbon dioxide permeabilities by a factor of 2–3.
H. Strathmann - One of the best experts on this subject based on the ideXlab platform.
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Accelerated plasticization of thin-film composite membranes used in gas separation
Separation and Purification Technology, 2001Co-Authors: Matthias Wessling, M. Lidon Lopez, H. StrathmannAbstract:Permeation experiments with He, N2, O2 and CO2, have been carried out with double layer composite membranes consisting of a silicone rubber support layer and a thin polyimide layer determining the permeation properties. The estimated thickness of the polyimide layer in the composite membranes was between 1.5 and 4 microns. This paper describes the phenomenon of accelerated plasticization of such thin polyimide layers used in gas separation membranes. The pressure-normalized fluxes were determined at 5 bars for N2, O2 and in the range of 1?8 bars in the case of He and CO2. Helium permeation decreased with increasing feed pressure and no hysteresis behavior was found for successive increasing and decreasing feed pressure steps. For CO2, the pressure-normalized flux did not follow the typical behavior of glassy polymers but increased continuously with increasing feed pressure. Also, CO2 permeation showed a clear hysteresis effects resulting in an increasing permeability with time and an elevated magnitude in successive decreasing feed pressure steps. Hence, stronger plasticization effects in the composite membranes must be concluded in comparison with thick single film membranes. The plasticization effects are significantly pronounced as the polyimide concentration in the solution from which the membranes are cast become more dilute. The latter is interpreted as accelerated plasticization with decreasing film thickness.
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suppression of gas separation membrane plasticization by homogeneous polymer blending
Aiche Journal, 2001Co-Authors: A Bos, H. Strathmann, Ineke G M Punt, Matthias WesslingAbstract:Plasticization is a phenomenon frequently encountered in the application of glassy polymeric materials for solution-diffusion membranes. Conventional methods for stabilizing the membrane are either annealing or cross-linking, which hardly influence the selectivity of the membrane, but decrease the permeability. For single-gas experiments, the literature shows that plasticization can be stabilized by blending a polymer with high plasticization tendencies with one that is hardly affected by the sorbed molecules. Most permeation experiments are carried out with pure CO2, but little is known about the transport properties determined from mixed gas experiments. Stabilization of plasticization in mixed-gas experiments for polymer blends of the polyimide Matrimid and polysulfone is reported, as well as transport properties of a new homogeneous polymer blend based on Matrimid and the copolyimide P84. Experimental results show that the material is stabilized against carbon dioxide plasticization and selectivity for a carbon dioxide/methane mixture significantly improves.
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co2 induced plasticization phenomena in glassy polymers
Journal of Membrane Science, 1999Co-Authors: A Bos, Matthias Wessling, Ineke G M Punt, H. StrathmannAbstract:A typical effect of plasticization of glassy polymers in gas permeation is a minimum in the relationship between the permeability and the feed pressure. The pressure corresponding to the minimum is called the plasticization pressure. Plasticization phenomena significantly effect the membrane performance in, for example, CO2/CH4 separation processes. The polymer swells upon sorption of CO2 accelerating the permeation of CH4. As a consequence, the polymer membrane loses its selectivity. Fundamental understanding of the phenomenon is necessary to develop new concepts to prevent it. In this paper, CO2-induced plasticization phenomena in 11 different glassy polymers are investigated by single gas permeation and sorption experiments. The main objective was to search for relationships between the plasticization pressure and the chemical structure or the physical properties of the polymer. No relationships were found with respect to the glass-transition temperature or fractional free volume. Furthermore, it was thought that polar groups of the polymer increase the tendency of a polymer to be plasticized because they may have dipolar interactions with the polarizable carbon dioxide molecules. But, no dependence of the plasticization pressure on the carbonyl or sulfone density of the polymers considered was observed. Instead, it was found that the polymers studied plasticized at the same critical CO2 concentration of 36±7 cm3 (STP)/cm3 polymer. Depending on the polymer, different pressures (the plasticization pressures) are required to reach the critical concentration.
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suppression of co2 plasticization by semiinterpenetrating polymer network formation
Journal of Polymer Science Part B, 1998Co-Authors: A Bos, Matthias Wessling, Ineke G M Punt, H. StrathmannAbstract:CO2-induced plasticization may significantly spoil the membrane performance in high-pressure CO2/CH4 separations. The polymer matrix swells upon sorption of CO2, which accelerates the permeation of CH4. The polymer membrane looses its selectivity. To make membranes attractive for, for example, natural gas upgrading, plasticization should be minimized. In this article we study a polymer membrane stabilization by a semiinterpenetrating polymer network (s-ipn) formation. For this purpose, the polyimide Matrimid 5218 is blended with the oligomer Thermid FA-700 and subsequently heat treated at 265°C. Homogeneous films are prepared with different Matrimid/Thermid ratios and different curing times. The stability of the modified membrane is tested with permeation experiments with pure CO2 as well as CO2/CH4 gas mixtures. The original membrane shows a minimum in its permeability vs. pressure curves, but the modified membranes do not indicating suppressed plasticization. Membrane performances for CO2/CH4 gas mixtures showed that the plasticizing effect indeed accelerates the permeation of methane. The modified membrane clearly shows suppression of the undesired methane acceleration. It was also found that just blending Matrimid and Thermid was not sufficient to suppress plasticization. The subsequent heat treatment that results in the s-ipn was necessary to obtain a stabilized permeability.
Donald R Paul - One of the best experts on this subject based on the ideXlab platform.
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gas permeation in thin films of high free volume glassy perfluoropolymers part ii co2 plasticization and sorption
Polymer, 2015Co-Authors: Rajkiran R Tiwari, Zachary P Smith, Haiqing Lin, Benny D Freeman, Donald R PaulAbstract:Abstract Carbon dioxide (CO2) plasticization and sorption effects in both thick and thin films of “high free-volume” glassy perfluoropolymers were studied by monitoring CO2 permeability and by observing changes in the film thickness and refractive index with ellipsometry measurements. The film thickness, aging time, thermal history and CO2 exposure protocols have significant effect on the absolute CO2 permeability and plasticization behavior of both thick and thin films. The extent of CO2 plasticization increases as film thickness decreases and as the aging time is increased. The as-cast films showed higher plasticization compared to films which were annealed above Tg; however, the CO2 permeability of both the as-cast and annealed films continuously decreased during the depressurization step unlike other glassy polymers. In general, the various CO2 exposure protocols revealed lower CO2 plasticization for perfluoropolymers compared to other reported glassy polymers. The extent of CO2 sorption obtained from the ellipsometry measurements was found to decrease with the decrease in the excess volume and increase in the aging time for perfluoropolymers; in addition, the structural differences among the various glassy polymers resulting in different polymer–gas interactions also affects the overall sorption characteristics. The lower plasticization in perfluoropolymers compared to Matrimid was also confirmed from the smaller percent increase observed for the experimental diffusion coefficient compared to the theoretically predicted diffusion coefficient from the dual sorption-mobility model. The Langmuir sorption parameter, C H ′ , and solubility at infinite dilution, S0, obtained from fitting dual sorption-mobility model to sorption data, showed an excellent linear correlation with (Tg-35) °C. The CO2 diffusivity and permeability data obtained for thin films of various glassy polymers also showed a strong correlation with free volume. The somewhat unusual behavior of thin films of AF 2400 in comparison to other glassy polymers studied to date is believed to be related to the low cohesive energy density expected of perfluorinated structures and its high free volume resulting from the bulky dioxole comonomer.
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gas separation performance of 6fda based polyimides with different chemical structures
Polymer, 2013Co-Authors: Wulin Qiu, Donald R Paul, Chienchiang Chen, William J KorosAbstract:Abstract 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 CO 2 and CH 4 transport and plasticization stability of the polyimides membranes relevant to natural gas purification. The consideration of the other gases (He, O 2 and N 2 ) 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 CO 2 plasticization responses for the un-cross-linked polyimides showed good plasticization resistance to CO 2 /CH 4 mixed gas with 10% CO 2 ; however, only the cross-linked polyimides showed good plasticization resistance under aggressive gas feed conditions (CO 2 /CH 4 mixed gas with 50% CO 2 or pure CO 2 ). For future work, asymmetric hollow fibers and carbon molecular sieve membranes based on the most attractive members of the family will be considered.
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carbon dioxide plasticization and conditioning effects in thick vs thin glassy polymer films
Polymer, 2011Co-Authors: Norman R Horn, Donald R PaulAbstract:Abstract Recent studies have shown that thin glassy polymer films undergo physical aging more rapidly than thick films. This suggests that thickness may also play a role in the plasticization and conditioning responses of thin glassy films in the presence of highly-sorbing penetrants such as CO2. In this paper, a carefully designed systematic study explores the effect of thickness on the CO2 plasticization and conditioning phenomena in Matrimid®, a polyimide commonly used in commercial gas separation membranes. Thin films are found to be more sensitive than thick films to CO2 exposure, undergoing more extensive and rapid plasticization at any pressure. The response of glassy polymers films to CO2 is not only dependent on thickness, but also on aging time, CO2 pressure, exposure time, and prior history. Finally, thin films experiencing constant CO2 exposure for longer periods of time exhibit an initial large increase in CO2 permeability, which eventually reaches a maximum, followed by a significant decrease in permeability for the duration of the experiment. Thick films, in contrast, do not seem to exhibit this trend for the range of conditions explored.
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the effects of crosslinking chemistry on co2 plasticization of polyimide gas separation membranes
Industrial & Engineering Chemistry Research, 2002Co-Authors: John D Wind, Donald R Paul, Claudia Staudtbickel, William J KorosAbstract:To suppress undesirable plasticization effects in CO2/CH4 separations, crosslinkable 6FDA-based copolyimides were synthesized by using 3,5-diaminobenzoic acid (DABA) as one of two diamine monomers. DABA contains a carboxylic acid group that can be used to crosslink the polymer chains with ethylene glycol and aluminum acetylacetonate. These chemistries were compared for effectiveness in suppressing CO2 plasticization on the basis of pure CO2 permeation and sorption data up to 800 psia. The time and pressure dependencies of permeation and sorption were analyzed to characterize the plasticization phenomenon and how it can be controlled by covalent crosslinking. Mixed-gas permeation data are reported up to a total feed pressure of 850 psia for the separation of 50:50 CO2/CH4 mixtures at 35 °C. Selectivity losses with increasing feed pressure are modeled to further understand the effects of plasticization, dual-mode sorption, gas-phase nonidealities, and bulk flow on membrane performance. Additionally, a short...