We all know that solvent (in the membrane film)/water (in the bath) replace in the coagulation bath because of the high miscibility between them. Can any researcher explain this phenomena deeper, please? Thanks.
Phase Separation (PS) or Phase Inversion (PI) is among the principal techniques for membrane preparation. The membrane matrix and the membrane pores are formed, respectively, from the polymer-rich and the polymer-lean phases originated by the phase separation of an initially homogeneous polymeric dope. Immersion of a cast (or spun) polymeric dope in a coagulation bath is normally used in nonsolvent (or diffusion)-induced phase separation (NIPS or DIPS), also called immersion precipitation (IP), to achieve such separation, often referred to as demixing or precipitation as well. Upon immersion in the coagulation bath, the initial composition of the dope changes as the solvent diffuses in the bath and is gradually replaced by the nonsolvent. Polymer precipitation due to solvent/nonsolvent (S/NS) exchange is exploited both in flat sheet and hollow fiber preparation via NIPS. However, for flat sheet membranes, the cast polymer film is immersed in the coagulation bath and phase inversion.
Immediately upon immersion of the polymer gel in the coagulation bath, the fast solvent-coagulant exchange across the interface combined with the large repulsive forces between polymer and coagulant cause an immediate precipitation at the interface. This process is too fast for any segregation of the Nomex particles.
The choice of the appropriate coagulation medium represents a significant aspect in membrane preparation. The miscibility between solvent (in which the polymer is dissolved) and non-solvent can affect, in fact, the final structure of the membrane.
Dear Emmanuel,
Thanks for your reply and information. But I need to know more.
Regards
- Badges
- Science topic
- Similar topics
- Philosophy
- Philosophy Of Science
- Reasoning