Mechanism of the mixed matrix membrane (polyethylene glycol/silicone rubber) separation for polar gases

Abstract

An emerging membrane morphology with future potential is mixed matrix membrane composed of two different materials. In this study, mixed matrix membranes of silicone rubber and polyethylene glycol (PEG) were prepared by coating polymer solution on porous support. The permeation rates of CO₂, H₂, N₂ and C₂H₆ were evaluated through a dense homogeneous silicone rubber membrane and silicone rubber-PEG mixed matrix membrane. For the mixed matrix membrane, gas permeances slightly decreased while the selectivities of polar gas/non-polar gas were significantly improved due to the enhancement in solubility of polar gases in PEG. Observed permeance dependence with respect to type of backing for silicone rubber-PEG mixed matrix membrane indicates that PEG not only has the capacity of altering the permeability of silicone rubber which it is mixed, but also acts on the polymeric support material by softening it and causing its pore to shrink. Higher selectivity was obtained at higher PEG composition. This indicates that PEG is an excellent solvent for selective permeation of polar gases.