The difference between the two membrane materials in definition and molecular structure Polyvinylidene fluoride (PVDF) is a highly non-reactive pure thermoplastic fluoropolymer. PVDF is a chain of carbon atoms with two fluorine atoms and two hydrogen atoms attached to each carbon. The molecular formula is -(- CF2-CH2-)-, due to the presence of fluorine atoms, gives PVDF chemical resistance and thermal stability, so it is often used in applications that require high purity, strength, and resistance to solvents, acids, alkalis, and heat. PAN (polyacrylonitrile) is a synthetic semi-crystalline organic polymer resin with a backbone of carbons, each carbon attached to a hydrogen atom, a nitrile group (-CN), and another carbon or hydrogen atom, with the molecular formula is -(-CH2-CH(CN)-)-, where the nitrile group makes PAN more polar and hydrophilic than PVDF.

The difference between PVDF membrane and PAN membrane in characteristics

1. In terms of chemical resistance, PVDF has excellent chemical resistance, which is mainly suitable for corrosive chemical environments, such as strong acid and strong alkali environments, sulfuric acid, hydrochloric acid and nitric acid, sodium hydroxide and potassium hydroxide, etc., many organic solvents such as alcohols, esters, ketones, and hydrocarbons, and can also withstand exposure to certain halogenated solvents. PAN, on the other hand, has good resistance to most inorganic chemicals, low organic solvents, and weak acids, and is generally resistant to water, alcohols, and certain hydrocarbons, but compared with PVDF membranes, it is less resistant to strong acids and alkalis. Poor, degrades or degrades when exposed to concentrated acids or bases.

2. In terms of thermal stability, PVDF can withstand higher operating temperatures. Generally speaking, PVDF films can withstand temperatures from -40°C to 150°C without significant loss of mechanical or electrical properties. Compared with PVDF, PAN has lower thermal stability, and PAN film can usually withstand temperatures from -30°C to 80°C (some can reach 100°C) without significant degradation, and beyond this range , deformation and shrinkage will occur.

3. Mechanical strength: PVDF has high mechanical strength and can provide good membrane support. Similarly, PAN also has high mechanical strength and can be used as a good substrate.

4. In terms of anti-biofouling, due to its hydrophobicity, PVDF helps to resist biofouling. PAN has advantages over PVDF in terms of hydrophilicity, which can enhance water permeability and resist protein contamination.

5. In terms of adaptability in the application industry, PVDF is often used as the substrate for nanofiltration and reverse osmosis membranes, especially when the feed stream has high organic content or a higher operating temperature is expected. The PAN membrane is more suitable for ultrafiltration membranes and some nanofiltration and reverse osmosis membrane substrates, especially when water permeability and antifouling properties are given priority, it is especially suitable.

The above summary of principles and characteristics, regarding the distinction between PVDF membrane and PAN membrane as reverse osmosis or ultrafiltration membrane substrate, I hope it can help the application partners, or add some references when making membrane selection.