Choose Lab Microporous Filter Membranes From Several Aspects
The main function of the microporous filter membrane is to trap particles, bacteria, and other impurities from the gas or liquid phase to achieve the purpose of separation, purification, and purification. Therefore, the following factors should be considered when choosing a filter membrane:
1. The material of the filter membrane (chemical compatibility): When choosing a filter membrane, first consider the chemical compatibility. Whether the filter is resistant to acid, alkali, organic solvent, etc.
(1) Cellulose esters such as CA; CTA; CN; EC; CN-CA, etc. Among them, the filter membrane made of mixed cellulose is a standard and common filter membrane. Due to its good pore-forming performance, good hydrophilicity, easy-to-obtain materials, and low cost, the pore size of the filter membrane are graded more, from 0.05 to 8um, there are about ten pore sizes. The membrane has a wide temperature range. Can withstand dilute acid. Not suitable for the filtration of liquids such as ketones, esters, strong acids, and alkalis.
(2) Polyamides such as nylon 6 and nylon microporous filter membranes. This species also has hydrophilic properties. More alkali-resistant but not acid-resistant. It is not easy to be corroded in ketones, phenols, ethers, and high molecular weight alcohols. There are also many aperture models. It is suitable for the purification of photoresist and developer in the electronics industry.
(3) Polysulfones such as polysulfone (PS) and polyethersulfone (PES) microfiltration filter membranes. This type of film has good chemical and thermal stability, radiation resistance, high mechanical strength, and a wide range of applications.
(4) Fluorine-containing materials such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene membrane (PTFE). This type of microfiltration membrane has excellent chemical stability and is suitable for use at high temperatures. Especially the PTFE filter membrane, its use temperature is -40～260℃, it can withstand strong acid, strong alkali, and various organic solvents. Due to its hydrophobicity, it can be used to filter the vapor and various corrosive liquids.
(5) Polycarbonate and polyester are mainly used to make nuclear porous membranes. The pore diameter of the nuclear pore filter membrane is very uniform, and the thickness is generally 5～15um. The porosity of this filter membrane is only ten percent. Because the membrane is thin, the fluid filtration speed is equivalent to that of the previous membranes. However, the production process is more complicated, the film price is high, and the application is limited. At present, the nuclear membrane can be made into various pore sizes.
(6) Polyolefins such as polypropylene (PP) stretched microporous filter membranes and polypropylene (PP) fiber deep filtration membranes. This type of microporous membrane has good chemical stability and is resistant to acids, alkalis, and various organic solvents. cheap price. However, this type of membrane has a wide pore size distribution. The current commercial membranes have a variety of configurations of flat type and hollow brazing type. And has a variety of aperture specifications.
(7) Inorganic materials such as ceramic microporous filter membranes, glass microporous filter membranes, and various metal microporous membranes. This is a new family of microporous membranes that have received much attention in recent years.
The inorganic film has the advantages of high temperature resistance, organic solvent resistance, and biodegradation resistance. Especially in high temperature gas separation, filter membrane catalytic reactor, and food processing industries, it has good application prospects.
2. The pore size of the filter membrane: determine the correct range of filter membrane pore size according to the size of the molecules or particles that need to be filtered.
3. The characteristics of the sample:
1) Hydrophilic samples: use hydrophilic membranes. It has an affinity for water and is suitable for filtering water-based solutions. Available filter membranes are mixed cellulose membrane, polyethersulfone (PES), Nylon, etc.
2) Strongly corrosive organic solvents: generally use hydrophobic membranes. Such as PTFE, polypropylene (PP), and other materials filter membranes.
3) Protein solution: Choose a filter membrane with low protein adsorption, such as PVDF filter membrane.
4) Ion chromatography: PES filter membrane is generally considered to be more suitable for filtering solutions with low inorganic ions.