Ts. Chung et Er. Kafchinski, THE EFFECTS OF SPINNING CONDITIONS ON ASYMMETRIC 6FDA 6FDAM POLYIMIDEHOLLOW FIBERS FOR AIR SEPARATION/, Journal of applied polymer science, 65(8), 1997, pp. 1555-1569
We have found that the chemistries of inner and external coagulants, g
elation bath temperature, and air gap distance have profound effects o
n 6FDA-polyimde hollow-fiber morphology and performance. This 6FDA-pol
yimide is made of 50 mol % 2,2'-bis(3,4'-dicarboxyphenyl) hexafluoro p
ropane dianhydride (6FDA) and 50 mol % 2,2'-bis(S-aminophenyl)hexafluo
ro propane (4,4' GF-diamine)(6FDAM). An increase in air gap distance t
ends to induce three-dimensional open-cell pore formation. Raising bat
h temperature has a similar effect. Multilayer finger-void structure c
an be completely eliminated if one properly chooses a bore-fluid flow
rate and a gelation bath temperature. Experimental data demonstrate th
at the location of the dense layer can be shifted from the inner skin
to the outer skin based on the chemistry (solubility parameter) of coa
gulants. The location of finger voids is also dependent on the chemist
ry of coagulants, and the dense layer location may shift from the inne
r surface to the external surface or appear in both surfaces dependent
on the differences in solubility and coagulation rate. A defect-free
6FDA/6FDAM polyimide fiber with a selectivity of 4.73 and a permeance
of 38.1 GPU is produced. (C) 1997 John Wiley & Sons, Inc.