The composite membrane is a microporous membrane or ultrafiltration membrane as a branch layer, and the surface is covered with a separation membrane composed of a dense homogeneous membrane with a thickness of only 0.1-0.25 μm as a barrier layer. Makes the amount of substance permeated greatly increased.
The preparation methods are divided into four categories:
1. Laminating method, first prepare a very thin dense homogeneous film, and then laminate it on the microporous supporting film;
2. Dip coating method: Dip the polymer solution on the microporous membrane and then dry it. Alternatively, the reactive monomer or prepolymer solution can be dip coated on the microporous membrane and cured with heat or radiation;
3. The plasma vapor deposition method uses plasma glow to produce a dense homogeneous film on the surface of the microporous supporting film;
4. Interfacial polymerization method, on the surface of the microporous supporting membrane, interfacial polymerization with active monomers.