Phase Inversion and Flat Membrane Production
Phase inversion stands for a process where we intentionally trigger a phase separation in an originally homogeneous solution.
The phase separation can be induced by two different processes:
1. Change in temperature (TIPS – thermally induced phase inversion) or 2. Change of solvent – which is in this case a non-solvent for the respective polymer. In scenario 1 (TIPS) an organic compound operates as the solvent for the respective polymer at high temperatures and as a non-solvent at low temperatures. The isothermal process to exchange a solvent by a non-solvent is more commonly used.
Flat membrane production
In the context of the flat membrane production the homogeneous polymeric solution is being spread thinly onto a porous non-woven material. The non-woven serves as supporting structure for the membrane being produced. The non-woven with the polymeric solution is immersed into a precipitation bath filled with a non-solvent. Caused by diffusion, solvent and non-solvent exchange in the precipitation bath: the membrane precipitates (so called phase separation). The phase rich in polymers forms the porous matrix – the phase poor in polymers forms the pores of the membrane.