Gas transport properties of 6FDA-durene/1,4-phenylenediamine (pPDA) copolyimides

Abstract

We have determined the gas transport properties of He, H2, O2, N2, and CO2 for 6FDA‐durene homopolymer and 6FDA‐durene/pPDA copolyimides. The 6FDA‐durene exhibits the highest permeability with the lowest selectivity. Permeability of copolymers decreases with increasing 6FDA–pPDA content, while permselectivity increases with an increase in 6FDA–pPDA content. 6FDA‐durene/pPDA (50/50) and 6FDA‐durene/pPDA (20/80) materials have O2 and CO2 permeabilities greater than those calculated from the addition rule of the semilogarithmic equation. These higher deviations from the additional rule of the semilogarithmic equation are mainly attributed to the fact that these copolyimides have higher solubility coefficients than those calculated from the additive rule. The Tg s of 6FDA‐durene/pPDA copolyimides decrease with an increase in 6FDA–pPDA content. Tg s predicted from the Fox equation are lower than the experimental data, and the their difference increases with an increase in pPDA content, implying the copolyimides of 6FDA‐durene/pPDA may have greater interstitial space among chains because of the conformation difference, and thus create more fraction free volume compared with the ideal case of simple volume addition. Density measurements also suggest these two copolymers have greater free volumes and the fractions of free volume, which supporting the gas transport results. The thermal stability and β‐relaxation temperature have also been studied for these copolymers. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2703–2713, 2000

Symmetric and Asymmetric Zeolitic Imidazolate Frameworks (ZIFs)/Polybenzimidazole (PBI) Nanocomposite Membranes for Hydrogen Purification at High Temperatures

“…[ 56 ] All the tests were carried out at 35 ° C with an upstream pressure of 3.5 atm. The permeation cell confi guration and operating procedure had been described elsewhere.…”

Highly permeable chemically modified PIM-1/Matrimid membranes for green hydrogen purification

“…The pure gas permeability of PIM-1/Matrimid membranes was measured using a variable-pressure constant-volume gas permeation cell reported elsewhere. 37 Pure gas permeability was tested in the sequence of H 2 , O 2 , N 2 , CH 4 , and CO 2 at 35 o C and 3.5 atm. The rate of pressure increase (dp/dt) at steady state was used to calculate gas permeability as follows: (4) where P is the gas permeability of a membrane in Barrer (1 Barrer = 1 x 10 -10 cm 3 (STP) cm/cm 2 s.cmHg), V is the volume of the downstream chamber (cm 3 ), A refers to the effective membrane area (cm 2 ), l is the membrane thickness (cm), T is the operating temperature (K), p 2 is defined as the upstream operating pressure (psia).…”

A governing equation for physical aging of thick and thin fluoropolyimide films

“…37 For the intermediate and thin films (0.5-5 m), a different drying procedure was adopted. Films with a ceramic support were put in the oven to dry at 60°C under vacuum for 24 h. Subsequently, the temperature was increased from 60 to 250°C at a heating rate of 12°C/20 min.…”

“…A detailed description of the apparatus (permeation cell) design and testing conditions can be found elsewhere. 37 The ideal permselectivity is defined as follows: ␣ A/B ϭ P A /P B . It is noteworthy that the X-ray photoelectron spectroscopy (XPS) results of the original (as-cast) and tested samples show no significant difference.…”