The Main Classification of Microporous Filter Membrane
(1) Cellulose esters
This system includes cellulose diacetate (CA), cellulose triacetate (CTA), nitrocellulose (CN), ethyl cellulose (EC), mixed cellulose (CN-CA), etc. Among them, the standard and common filter membrane is the mixed cellulose membrane. Due to its good pore-forming performance, good hydrophilicity, easy-to-obtain materials, and low cost, the pore size of the membrane are ranging from 0.05 to 8um, and there are about ten pore sizes. The membrane has a wide temperature range, which can withstand dilute acid. It is not suitable for filtering liquids such as ketones, esters, strong acids, and alkalis.
It includes nylon 6 (PA-6) and nylon (PA-66) microporous membranes. This species also has hydrophilic properties, alkali-resistant but not acid-resistant. In ketones, phenols, ethers, and high molecular weight alcohols, it is not easy to be corroded. There are also many aperture models. The polyamides microporous membranes are frequently used in the electronics industry for the purification of photoresists and developers.
Polysulfones include polysulfone (PS) and polyethersulfone (PES) microfiltration membranes. This type of membrane has good chemical and thermal stability, radiation resistance, high mechanical strength, and a wide range of applications.
(4) Fluorine-containing materials
Fluorine-containing materials include polyvinylidene fluoride (PVDF) and polytetrafluoroethylene membrane (PTFE). With excellent chemical stability, it is more suitable for high temperatures applications, up to 260℃, which is resistant to strong acid, alkali, and organic solvents. Due to its hydrophobicity, it can be used to filter vapor and various corrosive liquids. Please click here to know PVDF vs PTFE.
(5) Polycarbonate and polyester
They are mainly used to make nuclear porous membranes. The diameter of the pores of the nuclear membrane is very uniform, and the thickness is generally 5-15um. The porosity of this membrane is only ten percent. Because the membrane is thin, the fluid filtration speed is equivalent to that of the previous filter membranes. But, due to the more complicated production process and high cost, it has limited applications. For now, various pore sizes of the nuclear membranes are available.
Polyolefins include polypropylene (PP) stretched microporous membranes and polypropylene (PP) fiber deep filtration membranes. It features excellent chemical stability, resistance to acids, alkalis, and various organic solvents, which is much more cost-effective. However, this type of filter membrane has a wide pore size distribution. For the current commercial membranes, many different types are available, such as the flat one and hollow brazing type, which have many aperture specifications.
(7) Inorganic materials
Inorganic materials include ceramic microporous membranes, glass microporous membranes, and various metal microporous membranes. This is a new family of microporous membranes that have received much attention in recent years, with features of resistance to high temperature, organic solvent resistance, and biodegradation. Especially in high-temperature gas separation, membrane catalytic reactor, and food processing industries, it has good application prospects.