Gas separation properties of aromatic poly(amide-imide) membranes

Aromatic poly(amide-imide)s were synthesized using direct 2,2-bis[N-(4-carboxyphenyl)-phthalimidyl] hexafluoropropane (6FDIA) polycondensation with various diamines containing flexible ether groups and bulky substituents. The oxygen and nitrogen gas transport in the poly(amide-imide) membranes was investigate at 35 °C with the pressure between the interval at 2-10 atm. The proposed method is expected to promote the gas permeability of the poly(amide-imide) membrane and maintain the gas selectivity. It was found that both gas permeability and selectivity of poly(amide-imide) membranes increased with increasing fractional free volume and d-spacing. The gas permeability had good correlation with the γ-transition temperature. The bulky pendent group introduced into diamine moiety of poly(amide-imide) could efficiently promote the gas permeability. For the behaviors of gas separation, the gas diffusivity coefficient and solubility selectivity controlled the gas permeability and selectivity, respectively. The sorption behavior of the aromatic poly(amide-imide) membranes can be well explained using the dual mode sorption model. The Langmuir capacity constant and Henry’s law constant increase with FFV increasing. 6F-TBAPS has the best O₂/N₂ separation performance among the poly(amide-imide) membranes.     

Synthesis and Gas Permeability of Cyclotetrasiloxane-Containing Methacrylate Copolymers

Abstract

Synthesis and gas permeability of random and block copolymers of a cyclotetrasiloxane-containing methacrylate have been studied in comparison with those of tris(trimethylsiloxy)silane-containing methacrylate (MTTS) copolymers. Random and block copolymers of 3-(heptamethyl cyclotetrasiloxanyl) propyl methacrylate (HCPM) and methyl methacrylate (MMA) were prepared by radical copolymerization using 2,2′-azobisisobutyronitrile and a poly(azoinitiator), poly(1,6-hexamethylene 4,4′-azobiscyanopentanoate), respectively. Differential scanning calorimetry (DSC) revealed that HCPM-MMA block copolymers exhibited heterogeneous phases, as evidenced by two distinct glass transition temperatures due to poly-HCPM (PHCPM) block and PMMA block, while the single glass transition temperatures in the homogeneous phases in HCPM-MMA random copolymers lowered with HCPM content. The oxygen and nitrogen gas permeability coefficients of HCPM-MMA random copolymer films measured at 23°C were found to steeply increase with HCPM contents, although those of HCPM-MMA block copolymers slightly increased. The permeability coefficients of MTTS-MMA random copolymers prevailed over those of HCPM-MMA random copolymers despite the same four Si atoms, probably because of its free volume effect. Further, the HCPM content dependency on the diffusion and solubility coefficients, and the effect of crosslinking on their gas permeability were also discussed.     

Gas Permeability of Poly (organophosphazenes)

Abstract

The gas permeability and an oxygen to nitrogen selectivity was determined with some poly (organophosphazenes). It is found from the data that the membrance having the highest gas permeability was [NP(NHPrⁿ) (NHEt)]_n, and had 1.5x10^?6 cm^3. cm/cm³ sec.cmHg to oxgen or 2.2x10^?6cm³.cm/cm³.sec.cm.Hg to nitrogen. On the other hand, the membrance having the highest oxgen to nitrogen selectivity of about 3, had the formular of [NP(OC₆H₄Cl-p)₂]_n. Also, the selectivity does not depend on the glass transition temperature of the membrances. The membrance prepared from [NP(OC₆H₄CH₃-p)₂]_n has a negative activation energy to oxgen and nitrogen permeability.     

Cross‐linked Multilayer Polymer‐Clay Nanocomposites and Permeability Properties

Abstract

Electrostatically layered aluminosilicate nanocomposites have been prepared by the sequential deposition of poly(allylamine hydrochloride)/poly(acrylic acid)/poly(allylamine hydrochloride)/saponite (PAH/PAA/PAH/saponite)₁₀ on poly(ethylene terephtalate) (PET) film. Exfoliated saponite nanoplatelets were obtained by extensive shaking, sonication, and centrifugation of a water suspension. To minimize permeability and improve the mechanical integrity, cross‐linking of composite films was carried out at different temperatures. The formation of amide linkage induced through heating was observed by Fourier Transform Infrared (FT‐IR) and x‐ray photoelectron spectroscopy (XPS). The cross‐linking of nanocomposites (PAH/PAA/PAH/saponite)₁₀ showed 60% decrease in permeability of oxygen when compared with the pristine PET substrate film. In contrast, water permeability of the nanocomposite membrane was not affected by heating temperature and deposition cycles.     

Gas permeability and n‐butane solubility of poly(1‐trimethylgermyl‐1‐propyne)

The gas permeability and n‐butane solubility in glassy poly(1‐trimethylgermyl‐1‐propyne) (PTMGP) are reported. As synthesized, the PTMGP product contains two fractions: (1) one that is insoluble in toluene and soluble only in carbon disulfide (the toluene‐insoluble polymer) and (2) one that is soluble in both toluene and carbon disulfide (the toluene‐soluble polymer). In as‐cast films, the gas permeability and n‐butane solubility are higher in films prepared from the toluene‐soluble polymer (particularly in those films cast from toluene) than in films prepared from the toluene‐insoluble polymer and increase to a maximum in both fractions after methanol conditioning. For example, in as‐cast films prepared from carbon disulfide, the oxygen permeability at 35 °C is 330 × 10^?10 cm³ (STP) cm/(cm² s cmHg) for the toluene‐soluble polymer and 73 × 10^?10 cm³ (STP) cm/(cm² s cmHg) for the toluene‐insoluble polymer. After these films are conditioned in methanol, the oxygen permeability increases to 5200 × 10^?10 cm³ (STP) cm/(cm² s cmHg) for the toluene‐soluble polymer and 6200 × 10^?10 cm³ (STP) cm/(cm² s cmHg) for the toluene‐insoluble polymer. The rankings of the fractional free volume and nonequilibrium excess free volume in the various PTMGP films are consistent with the measured gas permeability and n‐butane solubility values. Methanol conditioning increases gas permeability and n‐butane solubility of as‐cast PTMGP films, regardless of the polymer fraction type and casting solvent used, and minimizes the permeability and solubility differences between the various films (i.e., the permeability and solubility values of all conditioned PTMGP films are similar). © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2228–2236, 2002     

Gas permeability and stability of poly(1-trimethylsilyl-1-propyne-co-1-phenyl-1-propyne) membranes

A significant reduction in the gas permeability of the poly(1-trimethylsilyl-1-propyne) (PMSP) membrane was investigated in terms of the membrane thickness and the storage environment. The effects of physical aging were observed with thinner membranes and under vacuum conditions compared with storage in air. The decrease in the permeability coefficient was dependent on the decrease in the hole saturation constant of Langmuir adsorption (C'_H), which is related to the volume of the microvoids. Physical aging in the PMSP membrane affected not only the glassy domain but also the rubbery one. To stabilize the permeability of the PMSP membrane, a poly(1-trimethylsilyl-1-propyne-co-1-phenyl-1-propyne) [poly(TMSP-co-PP)] membrane was prepared. Poly(TMSP-co-PP) has the same unit of poly(1-phenyl-1-propyne), which membrane has stable permeability. The poly(TMSP-co-PP) with less than 20 mol % PP content was estimated to be a random copolymer based on theoretical gas permeation analysis. In the poly(TMSP-co-PP) membrane, the relation between the PP content and C'_H was similar to the relation between the PP content and the gas permeability. The stability of the permeability was dependent on the PP content. The poly(TMSP-co-PP) membrane containing 10 mol % PP had both high permeability and good stability under some of the aging conditions performed in this work. © 1995 John Wiley & Sons, Inc.     

Synthesis and gas permeation properties of poly(diarylacetylene)s having substituted and twisted biphenyl moieties

Diarylacetylene monomers containing substituted biphenyl ( 1a – f ) and anthryl ( 1g ) groups were synthesized and then polymerized with TaCl₅‐n‐Bu₄Sn catalyst to produce the corresponding poly(diarylacetylene)s ( 2a – g ). Polymers 2a – f were soluble in common organic solvents such as cyclohexane, toluene, and chloroform. According to thermogravimetric analysis, the onset temperatures of weight loss of the polymers were over 400 °C in air, indicating considerably high thermal stability. Free‐standing membranes 2a and 2c – e were prepared by the solution casting method. Desilylation of Si‐containing membrane 2c was carried out with trifluoroacetic acid to afford 3c . All the polymer membranes, especially those having twisted biphenyl groups, exhibited high gas permeability; for example, their oxygen permeability (PO ₂) values ranged from 130 to 1400 barrers. Membrane 2d having two chlorine atoms in the biphenyl group showed the highest gas permeability (PO ₂ = 1400 barrers) among the present polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 861–868, 2010     

Oxyalkylene polymers with alkylsulfonylmethyl side chains: Gas barrier properties

Gas barrier properties of alkylsulfonylmethyl-substituted poly(oxyalkylene)s are discussed. Oxygen permeability coefficients of three methylsulfonylmethyl-substituted poly(oxyalkylene)s, poly[oxy(methylsulfonylmethyl)ethylene] (MSE), poly[oxy(methylsulfonylmethyl)ethylene-co-oxyethylene] (MSEE), and poly[oxy-2,2-bis (methylsulfonylmethyl)trimethylene oxide] (MST) were measured. MSEE, which has the most flexible backbone of the three polymers, had an oxygen permeability coefficient at 30°C of 0.0036 × 10⁻¹³ cm³(STP)·cm/cm²·s·Pa higher than that of MSE, 0.0014 × 10⁻¹³ cm³(STP)·cm/cm²·s·Pa, because the former polymer's T_g was near room temperature. MST with two polar groups per repeat unit and the highest T_g showed the highest oxygen permeability, 0.013 × 10⁻¹³ cm³(STP) · cm/cm²·s·Pa, among the three polymers, probably because steric hindrance between the side chains made the chain packing inefficient. As the side chain length of poly[oxy(alkylsulfonylmethyl)ethylene] increased, T_g and density decreased and the oxygen permeability coefficients increased. The oxygen permeability coefficient of MSE at high humidity (84% relative humidity) was seven times higher than when it was dry because absorbed water lowered its T_g. At 100% relative humidity MSE equilibrated to a T_g of 15°C after 2 weeks. A 50/50 blend of MSE/MST had oxygen barrier properties better than the individual polymers (O₂ permeability coefficient is 0.0007 × 10⁻¹³ cm³(STP)·cm/cm² ·s·Pa), lower than most commercial high barrier polymers. At 100% relative humidity, it equilibrated to a T_g of 42°C, well above room temperature. These are polymer systems with high gas barrier properties under both dry and wet conditions. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 75–83, 1998     

Oxygen permeability of surfactant/polymer composite films with multibilayer and inverted hexagonal structure

The permeability of oxygen through horizontally oriented multibilayer films of polyion complexes prepared from quaternary ammonium-type surfactants [CH₃(CH₂)_n-1]₂N⁺(CH₃)₂Br^?(n = 14, 16, 18), and poly(p-styrenesulfonate) or poly[2-(acrylamido)-2-methyl-1-propanesulfonate], was measured in water using an oxygen electrode. The permeability depended mainly on the phase of the multibilayers. Thus, it increased abruptly (about 10-fold) near each phase transition temperature because of the fluidity enhancement of the multibilayer. Inverted hexagonal type nonbilayer films prepared from the polyion complexes and cholesterol had greater permeability (2–20-fold) than the multibilayer films in both phases. The large permeability of the nonbilayer films was attributed to the lack of a barrier such as the bilayer and lower crystallinity of the films. It was associated neither with an increase in thermal movement of the lipid surfactant molecules nor with an increase in the water content of the films by the addition of cholesterol. © 1993 John Wiley & Sons, Inc.     

Gas Permeation Properties of Organic-Inorganic Hybrid Membranes Prepared from Hydroxyl-Terminated Polyether and 3-isocyanatopropyltriethoxysilane

Organic-inorganic hybrid materials were prepared by reacting 3-isocyanatopropyltriethoxysilane (IPTS) with hydroxyl terminated poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG) and poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) (PEPG), followed by hydrolysis and condensation with acid catalysis. Composite membranes have been obtained by casting hybrid sol on the microporous polysulfone substrate. The membranes were characterized by Fourier transform infrared (FT-IR), ¹³C NMR and ²⁹Si NMR. The permeability coefficients of N₂, O₂, CH₄ and CO₂ were measured by variable volume method. The gas permeability coefficients increase with increasing molecular weight of the polyethers. For the membranes containing PEG and PEPG, the higher values of CO₂ permeability coefficients and CO₂/N₂ separation factors are due to the presence of ethylene oxide segments. In case of PEPG membranes, molecular weight has more influence on CO₂ permeability than the effect of facilitation by ethylene oxide. The addition of TEOS into hybrid sol results in the decrease of all the gas permeability and does not affect the gas selectivity. PEG2000 membrane display the most performance among the hybrid membranes investigated here. The best values observed are CO₂ permeability of 94.2 Barrer with selectivity of 38.3 for CO₂/N₂ and 15.6 for CO₂/CH₄.     

XPS STUDIES ON SURFACE MODIFIED POLY [1-(TRIMETHYLSILYL)-1-PROPYNE] MEMBRANES Ⅱ SURFACE MODIFICATION BY BROMINE VAPOR*

Surface modification of poly [1-(trimethylsilyl)-1-propyne] (PTMSP) membranes bybromine vapor has been studied. It is shown that Br/C atomic ratio at the surfaces increased withthe time of bromination until about 60 min, then it reached a plateau. The results of XPS and IRstudies indicated that the addition of bromine to double bonds and the replacement of H on CH_3 bybromine had taken place so that a new peak at 286.0 eV (C--Br)in C_(1s) spectra and some newbands, e. g. at 1220 and 580cm~(-1) in IR spectra were formed. The fact,t Po_2, permeability ofoxygen, decreased and α_(O_2/N_2), separation factor of oxygen relative to nitrogen, increased withbromination time, shows that surface modification of PTMSP by bromine may be an efficient approach to prepare PTMSP membranes used for practical gas separations.     

Facilitated Transport of Molecular Oxygen in Membranes of Macromolecular Cobalt-Porphyrin Complex: Modification of Dual-Mode Transport Model

Transport of molecular oxygen is facilitated in poly(butyl methacrylate) membranes containing the cobalt(II)-α,α′,α″,α′″-meso-tetrakis(o-pivalamidophenyl)porphyrin-1-methylimidazole (CoPIm) complex which forms oxygen adduct rapidly and reversibly. The facilitated transport of oxygen is studied by modifying a dual-mode transport model for gas permeation. The diffusion coefficient of oxygen via the fixed CoPIm complexes (Langmuir mode) is assumed to depend on oxygen concentration, and the modified dual-mode transport equation is described for the permeation steady state. The modified equation represents the effect of upstream oxygen pressure on the permeability. The oxygen permeation behavior through the macromolecular-metal complex membrane is discussed.     

An investigation of the high gas permeability of poly (1-Trimethylsilyl-1-Propyne)

The permeability of poly (1–trimethylsilyl–1−propyne), PMSP, to light gases is higher than that of any other nonporous synthetic polymer at ambient temperatures. PMSP is in the glassy polymer state at these temperatures. Permeability, diffusion, and solubility coefficients were determined for N₂, O₂, CH₄, and CO₂ in PMSP, and are compared with values reported for these gases in poly (dimethyl siloxane). The higher gas permeability of PMSP results primarily from a substantial gas solubility, which appears to be due, in turn, to a large “excess” free volume in the unrelaxed (Langmuir) domains of this glassy polymer. The structure of PMSP, which consists of relatively rigid backbone chains separated by bulky trimethylsilyl side groups, probably is responsible for this large free volume.     

Synthesis and gas permeation properties of poly(4-methyl-2-pentyne)

Poly(4-methyl-2-pentyne) [PMP] is an amorphous, glassy, di-substituted acetylene-based polymer. PMP has a low density of 0.78 g/cm³ and a high fractional free volume of 0.28. The permeabilities for helium, hydrogen, nitrogen, oxygen, carbon dioxide, methane, ethane, propane, and n-butane were determined at temperatures from 20 to 65°C and pressures from 10 to 150 psig. PMP is the most permeable purely hydrocarbon-based polymer known; its permeabilities are only exceeded by poly(1-trimethylsilyl-1-propyne) [PTMSP] and poly(1-trimethylgermyl-1-propyne) [PTMGeP]. The oxygen permeability of PMP at 25°C is 2700 × 10⁻¹⁰ cm³(STP) cm/cm² s cmHg and the nitrogen permeability is 1330 × 10⁻¹⁰ cm³(STP) cm/cm² s cmHg. The high gas permeabilities in PMP result from its very high free volume, and probably, interconnectivity of the free-volume-elements. For a glassy polymer, PMP exhibits unusual organic vapor permeation properties. Permeabilities in PMP are higher for large, condensable gases, such as n-butane, than for small, permanent gases such as helium. The permeabilities of condensable gases and permanent gases decrease as the temperature is increased. This behavior is completely unexpected for a glassy polymer and has been observed previously in only high-free-volume glassy PTMSP.     

Effects of cross-linkers with different molecular weights in cross-linked Matrimid 5218 and test temperature on gas transport properties

The poly(ethylene oxide) (PEO) was introduced by the cross-linking method in the commercial Matrimid 5218. The two kinds of membranes were prepared from the Matrimid 5218 and the cross-linkers poly(propylene glycol) block poly(ethylene glycol) block poly(propylene glycol) diamine (PPG/PEG/PPGDA) with different molecular weights. The cross-linking reaction process was monitored by FTIR. The cross-linked Matrimid 5218 membranes display excellent CO₂ permeability and CO₂/light gas selectivity. The effects of cross-linkers with different molecular weights on gel content, thermal properties and H₂, CO₂, N₂ and CH₄ gas transport properties were reported. The effect of temperature on gas transport properties was also reported, and the permeabilities of these materials as a function of temperature were compared with other gas membrane materials.     

Improvement in gas permeability of biaxially stretched PET films blended with high barrier polymers: The role of chemistry and processing conditions

Improvement in oxygen gas barrier properties of polyester/polyamide blends used in packaging industry is the main objective of the present study. For this purpose poly(ethylene terephthalate) (PET)/poly(m-xylene adipamide) (nylon-MXD6) (95/5 w/w) and poly(ethylene terephthalate-co-isophthalate) copolymer (PETI)/MXD6 (95/5 w/w) blends have been prepared with a PET copolymer which consists of 5 wt.% sodium sulfonated isophthalate (PET-co-5SIPA) as compatibilizer and a carboxyl-terminated polybutadiene (CTPB) as filler by using a co-rotating intermeshing twin screw extruder. The effects of chemical architecture and morphology on oxygen gas permeability and processability were analyzed by using a range of characterization techniques including differential scanning calorimetry (DSC), scanning electron microscopy (SEM), oxygen gas permeability analyzer, and a special computer controlled uniaxial stretching system that provides real-time measurement of true stress, true strain and birefringence. The morphological analysis revealed that PET-co-5SIPA was an effective compatibilizer for both PET/MXD6 and PETI/MXD6 blends. DSC analysis and spectral-birefringence technique were used to understand the thermal and stress-induced crystallization behavior of the blends. Morphological analysis of the films after biaxial stretching indicated that the spherical nylon phase was converted to 75 nm thick disks during stretching (aspect ratio L/W = 6) that creates a tortuous pathway for oxygen ingress. Stretching enhanced the barrier properties of PET/MXD6 and PETI/MXD6 blends.     

Oxygen permeability of biodegradable copolycaprolactones

Polycaprolactone is one of the biodegradable polymers with good drug permeability. In the present paper, polycaprolactone and three kinds of copolycaprolactone–polycaprolactone–poly(ethylene oxide)– polycaprolactone triblock copolymer (PCE), polycaprolactone/polycaprolactone‐poly(ethylene oxide)/polylactide tricomponents random block copolymer (PCEL) and polycaprolactone/poly(ethylene terephthalate) random block copolymer (PETCL)– were synthesized. The biodegradation behavior of these polymers were shown by degradation tests in vitro, ex vivo and in vivo. The oxygen permeabilities of these polymers were in the range of 10⁻¹⁰ ∼ 10⁻⁹ cm³ (STP) cm/cm² sec cm Hg. Copolymers PCE and PCEL displayed O₂ and N₂ permeability coefficients (PO₂/PN₂) ratios of about 9. The effects of composition and crystallinity of the copolymers on biodegradability and the oxygen permeability of the polymer were discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Gas and vapor transport properties of amorphous perfluorinated copolymer membranes based on 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole/tetrafluoroethylene

Teflon AF 2400 (Du Pont) is an amorphous, glassy perfluorinated copolymer containing 87 mol% 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole and 13 mol% tetrafluoroethylene. The polymer has an extremely high fractional free volume of 0.327. Permeability coefficients for helium, hydrogen, carbon dioxide, oxygen, nitrogen, methane, ethane, propane, and chlorodifluoromethane (Freon 22) were determined at temperatures from 25 to 60°C and pressures from 20 to 120 psig. Permeation properties were also determined at a feed pressure of 200 psig at 25°C with a 2 mol% n-butane/98 mol% methane mixture. Permeabilities of permanent gases in Teflon AF 2400 are among the highest of all known polymers; the oxygen permeability coefficient at 25°C is 1600 × 10⁻¹⁰ cm³ (STP) cm/cm² s cmHg and the nitrogen permeability coefficient is 780 × 10⁻¹⁰ cm³ (STP) cm/cm² s cmHg. The permeabilities of organic vapors increase up to 20-fold as the vapor activity increases from 0.1 to unity, indicating that Teflon AF 2400 is easily plasticized. Although Teflon AF 2400 is an ultrahigh-free-volume polymer like poly(1-trimethylsilyl-1-propyne) [PTMSP], their gas permeation properties differ significantly. Teflon AF 2400 shows gas transport behavior similar to that of conventional, low-free-volume glassy polymers. PTMSP, on the other hand, acts more like a nanoporous carbon than a conventional glassy polymer.     

Gas permeability of cardo-poly(ether-ether-ketone) and poly(phenylene sulfide)

The gas permeability and sorption of CO₂ and N₂O was measured on cardo-poly(ether-ether-ketone) (C-PEEK) and poly(phenylene sulfide) (PPS) at 298 K. The results are discussed on the basis of the dual-mode model. Results obtained from measurements at 308 K are compared with literature data of poly(phenylene oxide) (PPO), poly(sulfone) (PSU) and poly(carbonate) (PC). While C-PEEK shows similar transport properties as PC and PSU, the values of PPS are distinctly lower. The solubility of CO₂ in the various polymers as well as the correlation of the permeability coefficients of the same polymers for He, Ar, CO₂, N₂, and CH₄ with the kinetic molecular diameter of the gases indicate a simple relation of the transport properties with the polymer density.     

Hydrocarbon/hydrogen mixed gas permeation in poly(1-trimethylsilyl-1-propyne) (PTMSP), poly(1-phenyl-1-propyne) (PPP), and PTMSP/PPP blends

The gas permeation properties of poly(1-trimethylsilyl-1-propyne) (PTMSP), poly(1-phenyl-1-propyne) (PPP), and blends of PTMSP and PPP have been determined with hydrocarbon/hydrogen mixtures. For a glassy polymer, PTMSP has unusual gas permeation properties which result from its very high free volume. Transport in PPP is similar to that observed in conventional, low-free-volume glassy polymers. In experiments with n-butane/hydrogen gas mixtures, PTMSP and PTMSP/PPP blend membranes were more permeable to n-butane than to hydrogen. PPP, on the other hand, was more permeable to hydrogen than to n-butane. As the PTMSP composition in the blend increased from 0 to 100%, n-butane permeability increased by a factor of 2600, and n-butane/hydrogen selectivity increased from 0.4 to 24. Thus, both hydrocarbon permeability and hydrocarbon/hydrogen selectivity increase with the PTMSP content in the blend. The selectivities measured with gas mixtures were markedly higher than selectivities calculated from the corresponding ratio of pure gas permeabilities. The difference between mixed gas and pure gas selectivity becomes more pronounced as the PTMSP content in the blend increases. The mixed gas selectivities are higher than pure gas selectivities because the hydrogen permeability in the mixture is much lower than the pure hydrogen permeability. For example, the hydrogen permeability in PTMSP decreased by a factor of 20 as the relative propane pressure (p/p_sat) in propane/hydrogen mixtures increased from 0 to 0.8. This marked reduction in permanent gas permeability in the presence of a more condensable hydrocarbon component is reminiscent of blocking of permanent gas transport in microporous materials by preferential sorption of the condensable component in the pores. The permeability of PTMSP to a five-component hydrocarbon/hydrogen mixture, similar to that found in refinery waste gas, was determined and compared with published permeation results for a 6-Å microporous carbon membrane. PTMSP exhibited lower selectivities than those of the carbon membrane, but permeability coefficients in PTMSP were nearly three orders of magnitude higher. © 1996 John Wiley & Sons, Inc.