Gas permeability and permselectivity of polyimides prepared from phenylenediamines with methyl substitution at the ortho position
✍ Scribed by Liu, Ye; Pan, Caiyuan; Ding, Mengxiang; Xu, Jiping
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 120 KB
- Volume
- 48
- Category
- Article
- ISSN
- 0959-8103
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✦ Synopsis
Polyimides were prepared from diamines: 2,4,6-trimethyl-1,3-phenylenediamine (3MPDA) and 2,3,4,5-tetramethyl-1,4-phenylenediamine (4MPDA). 1,4-Bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3'-4,4'-diphenylsulphone tetracarboxylic dianhydride (SO 2 PDA), 3,3',4,4'-diphenylsulphide tetracarboxylic dianhydride (SPDA), pyromellitic dianhydride (PMDA), and 2,2'-bis(3,4-dicarboxyphenyl)hexa-¯uoroisopropane dianhydride (6FDA) were used as dianhydride. The gas permeabilities of H 2 , O 2 and N 2 through the polyimides were measured at temperatures from 30 °C to 90°C. The results show that as methyl and tri¯uoromethyl substitution groups densities increase from 7.73 Â 10 À3 mol cm À3 to 13.50 Â 10 À3 mol cm À3 , the peameability of H 2 increases 10-fold at 60% loss of permselectivity of H 2 /N 2 ; however, the permeability of O 2 increases 20-fold at 20% loss of permselectivity of O 2 /N 2 . For O 2 /N 2 separation, PMDA-3MPDA has similar performance to 6FDA-3MPDA and 6FDA-4MPDA; all have higher permeabilities for O 2 than normal polyimides, and the P(O 2 )/a(O 2 /N 2 ) trade-off relationships lie on the upper bound line for polymers.