Membrane refers to different substances with different permeation rate of the film-like material. As a polyimide membrane material has the following characteristics:
1. It has a high thermal stability, so that the material can be obtained by separation at higher temperatures. Because the rate of material through the membrane increases with increasing temperature, but the selectivity also decreases with increasing temperature. Film having a high TG and high selectivity can be maintained at a higher temperature. Secondly, higher separation temperature is also beneficial substance.
2. With high mechanical properties, and then the film manufacturing operation of the device, the device also makes the film stand the higher operating pressure.
3. Effects of high solvent and other chemicals, to avoid working medium or other chemical impurities caused by damage to the structure of the film is reduced separation membrane, or even damage the membrane device.
4. Having a good film, you can select the casting solution and the coagulation bath composition over a wide range, to achieve excellent performance separation membrane.
5. Due to the diversity of the polyimide structure for different separation object from a large number of the existing structure, choose to give or design, synthesis of novel both a high selectivity coefficient, but also has a high coefficient of permeable membrane material .
Therefore, the polyimide has become a good candidate material for the separation membrane, particularly gas separation membranes. Recently polyimides are increasingly being used as a liquid membrane separation medium.