Synthesis, characterization, and gas permeation properties of 6FDA-2,6-DAT/mPDA copolyimides

• 来源期刊: 中国高等学校学术文摘·化学
• 关键词: 2 2'-bis(3 4'-dicarboxyphenyl) hexafluoro-propane dianhydride (6FDA) copolyimide permeability gas separation
• 年，卷（期）: 2009,（2）
• 页码范围: 215-221
• 页数: 7页
• 语种: 英文
• DOI: 10.1007/s11458-009-0028-5

摘要

The goal of this work is to explore new polyimide materials that exhibit both high permeability and high selectivity for specific gases. Copolyimides offer the possibility of preparing membranes with gas permeabilities and selectivities not obtainable with homopolyi-mides. A series of novel fluorinated copolyimides were synthesized with various diamine compositions by chemical imidization in a two-pot procedure. Polyamic acids were prepared by stoichiometric addition of solid dianhy-dride in portions to the diamine(s). The gas permeation behavior of 2,2'-bis(3,4'-dicarboxyphenyl) hexafluoro-propane dianhydride(6FDA)-2,6-diamine toluene (2,6-DAT)/ 1,3-phenylenediamine (mPDA) polyimides was investigated. The physical properties of the copolyimides were characterized by IR, DSC and TGA. The glass transition temperature increased with increase in 2,6-DAT content. All the copolyimides were soluble in most of the common solvents. The gas permeability coefficients decreased with increasing mPDA content. However, the permselectivity of gas pairs such as H2/N2, O2/N2, and CO2/CH4 was enhanced with the incorporation of mPDA moiety. The permeability coefficients of H2, O2, N2, CO2 and CH4 were found to decrease with the increasing order of kinetic diameters of the penetrant gases. 6FDA-2,6-DAT/mPDA (3:1) copolyimide and 6FDA-2,6-DAT polyimide had high separation properties for H2/N2, O2/N2, CO2/CH4. Their H2, O2 and CO2 permeability coefficients were 64.99 Barrer, 5.22 Barrer, 23.87 Barrer and 81.96 Barrer, 8.83 Barrer, 39.59 Barrer, respectively, at 35℃ and 0.2 MPa (1 Barrer =T-10cm3 (STP)·cm·cm-2·s1·cmHg 1) and their ideal permselectivities of H2/N2, O2/N2 and CO2/CH4 were 69.61, 6.09, 63.92 and 53.45, 5.76, 57.41, respectively. Moreover, all of the copolyimides studied in this work exhibited similar performance, lying on or above the existing upper bound trade-off lines between permselectivity and permeability. They may be utilized for commercial gas separation membrane materials.