| 초록 |
We synthesize and characterize a thermally stable polyimides (PI) based on benzophenone tetracarboxylic dianhydride (BTDA), 3,5-diaminobenzoic acid (DBA) and meta-phenylenediamine (mPDA). In this study, two types of carbon membranes were prepared. One is a random copolymer. The other is a block copolymer based on BTDA-mPDA-BTDA-DBA system. The understanding of the thermal decomposition and gas-evolving properties of precursor is instructive to determine the appropriate pyrolysis conditions by thermogravimetry-mass spectrometry (TG-MS). The gas transport properties of O2 and N2 for PI have been investigated as a function of the concentration of carboxylic acid group. He, CO2, O2 and N2 permeabilities slightly increased in the order of increasing mole ratio of DBA. This is probably due to the formation of a microporous structure as a result of decomposition of carboxylic acid groups. The membrane pyrolyzed at 500℃ show He, O2 and N2 permeability of 586, 122 and 15 [Barrer=1×10-10cm3(STP)cm/cm2 S cmHg], respectively, and He/N2 and O2/N2 separation factors of 38 and 8 at 25℃. |
