A TFC membrane can be considered a molecular sieve constructed in the form of a film from two or more layered materials.
The polyamide top layer is responsible for the high rejection and is chosen primarily for its permeability to water and relative impermeability to various dissolved impurities including salt ions and other small, unfilterable molecules.
[1] Although not fully commercialized yet, TFC's are also used in other water treatment technologies, including Forward osmosis,[2] membrane distillation,[3] and electrodialysis.
In 1972, John Cadotte of North Star Technologies (later FilmTec Corporation) developed the first interfacial polyamide (IP) thin-film-composite (TFC) membrane.
Today, most such membranes for reverse osmosis and nanofiltration use a Polyamide active layer.
As the water pressure increases, the polymers are slightly reorganized into a tighter fitting structure that results in a lower porosity, ultimately limiting the efficiency of the system designed to use them.
In applications other than filtration, parameters such as mechanical strength, temperature stability, and electrical conductivity may dominate.