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E. EFTIMIE TOTU1,* , E. RUSE1, I. GHICA DIACONU1
It was found that polyimides exhibit excellent thermal and mechanical properties for gas separation applications as they have an overall hydrolytic stability and good resistance to wear, radiation and inertness to solvents [1, 2, 3]. The polyimides membranes are most likely to be used in new installations made to transport gases through dense homogeneous membranes of polyimides as they combine a high permeability with a high selectivity when they are supposed to be at least as good as the competitive techniques. The work described herein aims to relate physicochemical polymer properties to various gases transport across polymeric membrane. Applying Askadskii [3] method to determine the packing density of the polymer used there was obtained a packing coefficient K equal by 0.67. Hence 33% of the polymeric matrix consists of free volume. The distribution of the free volume over smaller and larger holes is also very important in determining the rate of the gas diffusion. As below the glass transition point the structure may contain more free volume than could be expected from the difference in thermal expansion coefficient, we determined the Tg value applying DSC analysis. Also, there were performed thermal analyses of the polyimides studied in order to determine the pre-exponential factor A which is related to the amount of free volume. It could be considered a scaling factor to account for the total unoccupied volume of the system in its ground state.
Polyimide matrix, Kinetic parameters, TG analysis, Glass transition temperature, Softening temperature.
E. EFTIMIE TOTU, E. RUSE, I. GHICA DIACONU, Characterisation of polyimide membranes using thermochemical data, Optoelectronics and Advanced Materials - Rapid Communications, 3, 8, August 2009, pp.808-811 (2009).
Submitted at: July 7, 2009
Accepted at: July 31, 2009
Optoelectronics and Advanced Materials - Rapid Communications
(2023): 0.5 - 2023 Journal Citation Reports (Clarivate Analytics, 2024)
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