The Thermal Properties of Polyimide Membrane

Two new polyimides with aliphatic radical were synthesized. The aims are to break through the limit which aromatic polyimide is primarily material as gas separation membrane in polydride memrane materical, and to look for gas separation membrane materials with good permeability and selecivity. Tg, TGA and DSC of prepared polyimide membranes were determined. Studied the relationship between the structure and thermal properties of polyimides. From the results, it can be seen that the thermal properties of polyimides are related to their molecular structure, and all polyimides studied in here have good thermal properties.But the thermal properties of two novel polyimides with aliphatic radical are less than that of aromatic polyimide. There is a rank of glass transition temperature of the polyimides prepared by identical diamine with different dianhydrides as: PMDA ＞ CPDA ＞ BTDA ＞ BDA. The rank of glass transition temperature of the polyimides prepared by identical dianhydride with differnt diawines as : PMDA-Bz ＞ PMDA-DDA＞PMDA-MDA＞ PMDA-ODS; BTDA-TMPDA＞BTDA - Bz ＞ BTDA-DDS＞ BTDA - MDA ＞ BTDA - ODA; BDA - TMPDA ＞ BDA - Bz＞BDA-DDS ＞BDA-MDA ＞BDA-ODA; CPDA-TMPDA ＞CPDA-Bz ＞CPDA-DDS＞CPDA-MDA＞CPDA-ODA. The deremposition temperature （Td） and meting temperature（Tm） wer also determined. The rank of deremposition tempefature （Td） as : PMDA＞CPDA＞BPDA＞BDA＞BTDA, the tank of meting temperature （Td） as : PMDA＞CPDA＞BTDA＞BPDA＞BDA.