Organically modified clay as an enhancement filler in novel polyimide mixed matrix membranes for gas separation

Nanocomposite gas transport and thermally stable membranes-based fluorinated polyimide/clay were prepared. Novel polyimide (PI) membranes containing various amount of organically modified clay with the main intention to investigate the gas permeation behavior of the resultant material combination were prepared. The fabricated mixed matrix membranes (MMM)s were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and pure gas permeation testing. The dispersion morphology of these nanocomposites was confirmed by XRD and TEM analyses. The intercalation of PI chains among the clays particles were examined using wide-angle X-ray diffraction (XRD) and electron microscopy (TEM) techniques. TEM photographs showed that most clay layers were dispersed homogeneously into the matrix polymer on the nanoscale, although some particles of clays were agglomerated. Moreover, the addition of only a small amount of clays particles was enough to improve the thermal stabilities and mechanical properties of PI hybrid films. XRD and TEM analysis revealed that the layered silicate clay has been successfully exfoliated in the polymer matrix. The gas permeation properties were evaluated by pure gases: nitrogen, oxygen, methane, and carbon dioxide. Several interesting roles of layered silicate clay particle in determining the gas permeation behavior of the hybrid membrane have been discovered. It was no surprise that the gas permeation flux was decreasing with the addition of clays into the PI matrix. It was interesting to note that the pure gas selectivity was seen to be increased with decreasing the filler loading. At 1 wt% clay loading, PI/clay showed an increase of 55% in CO₂/CH₄ ideal selectivity over pristine PI membrane.