Critical concentration determination of polyetherimide membrane for gas separation

In preparation of gas separation membrane, polymer concentration is one of the most important variables which can change membrane morphology and behavior. It should be high as polymer chains engage with each other and made dense membrane for gas separation, in this concentration viscosity of polymeric solution has quirk. This concentration is called critical concentration. The studies on gas permeation in Polyetherimide (PEI) dense film reveal that PEI exhibits impressively high selectivity for all important gas pairs, there are a few solvents for PEI, in this research critical concentration of PEI in N-methyl-2-pyrrolidone and chloroform have been investigated.