.6 The Fda Polyimide Film Materials Synthesis And Gas Permeation Studies

In this study, a novel lithium sulfonate group-containing polyimide (6FDA-MLi) based on 6FDA was synthesized by a two-step method for the first time. The resulting polyimide was soluble in common solvents such as DMF, DMAc and NMP. It has high molecular weight and the limiting viscosity number was 5.07L/g. This polyimide exhibited good thermostability with a glalss transition temperature of 244℃ and 5% weight loss at 286℃.The effect of temperature, pressure on gas transport properties of H2, N2, O2, CH4 and CO2 for 6FDA-MLi polyimide dense membrane were investigated. The relationship ?between permeability, diffusivity, solubility and temperature were consistent with Arrhenius equation between 20 and 35℃. The pressure dependency of permeability, diffisivity and solubility could be explained by dual-sorption model and partial immobilization theory between 0.2 and 0.8MPa. With the increase of feed pressure, CO2-induced plasticization phenomena may occur and the plasticization pressure was about 0.4MPa. Compared with 6FDA-TMPDA polyimide, the addition of -SO3Li would bring a reduction of gas permeability and an increase of gas permselectivity. The CO2 permeability was 17.2Barrer with a CO2/CH4 ideal selectivity of 35.5 at 35℃ and 0.2MPa.