Detailed Introduction of Microporous Membrane Filter

Made of polymer chemical materials, adding pore-forming additives on the support layer after special treatment, the microporous filter membrane is one of the most widely used membranes. It is simple and fast to use and is widely used in scientific research, food inspection, chemical engineering, nanotechnology, energy and environmental protection, and many other fields.

Features of membrane filter

The microporous filter membrane is flammable, and it should be sealed, moisture-proof, and fire-proof during storage. With high porosity and low resistance, its main purpose is to filter out the particles and bacteria of liquid medicine, gas, oil, beverages, wine, electronic instruments, etc., so, it is also suitable for particles and bacteria detection. Microporous membranes are divided into the hydrophilic and hydrophobic membrane. Among the many microporous membranes currently available, PVDF materials are the most widely used and the most effective.

Classifications of membrane filter

1. Based on pore size and separation efficiency

According to the difference in pore size and separation efficiency, the filter membrane can be roughly classified as (from the largest pore to the smallest pore): gas separation membrane, dialysis/hemodialysis membrane, reverse osmosis membrane, ultrafiltration membrane, microporous membrane, and microporous membrane.
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At present, in addition to the large-scale application of desalination of seawater and brackish water and the production of pure water and ultra-pure water, due to the high efficiency and environmental protection of the separation, adsorption, diffusion, and other aspects of the filter membrane, it has also been widely used in pharmaceutical manufacturing processes, chemical engineering, beverage processing, semiconductor electronic washing, water purification, biochemical inspection and other fields, which have become one of the most important high-tech in the biochemical sciences of this century in the application of filtration, separation, inspection, and analysis.

Generally speaking, users of filter membranes use different types of membranes according to the different requirements of their application (filtration separation or inspection analysis). For example, the concentration of small molecules usually uses NF or RO membranes, while the clarification of large molecules uses UF or MF membranes. Due to their different characteristics and performance, each filter membrane plays an indispensable and important role in today’s diverse scientific and industrial applications.

2. Based on structural analysis

From the structural analysis of the microporous membrane, it is a very thin membrane with a porous sponge-like structure inside. Nowadays, manufacturers of microporous membranes classify them as follows according to their morphological differences: flat sheet membrane, hollow fiber membrane, and tubular membrane. Among them, the flat sheet membrane can be subdivided into “Unsupported” and “Supported” according to its structural differences. The unsupported production process is more sophisticated and than the supported ones.

Microporous filtration is a sieving process and belongs to precision filtration. To filter out 0.1 μm to 10 μm particles is what we called microporous precision filtration.

In general, there are two types of filtration mechanism, surface type, and deep layer type. The filtration mechanism of the MF membrane manufactured by technology is surface filtration. Because the filter aperture is fixed, the accuracy and reliability of the filter can be ensured. Deep filtration is divided into non-fixed irregular pore size and fixed irregular pore size. The former, such as a chemical fiber wound filter element, is generally only used as a rougher pre-filter.
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Following points to be noted when applying

①The bubble point should be determined: the bubble point pressure can reflect the pore size of the microporous membrane, which is closely related to the quality of the filtered liquid. The microporous membrane used should be soaked in water for injection at about 70℃ for 1h in advance. Pour out the water and soak it with warm water for injection for later use. Take it out just before use, rinse it with water for injection, then put it into the filter for use. When installation, prevent the filter membrane from crooked and leaking.

②In order to protect and extend the service life of the filter membrane, filter paper or silk cloth of the same size can be used (Take 30 min to boil the silk cloth with a mass concentration of 20 g·L-1 sodium sulfonate solution, and take several min to wash it with water for injection). Put it on the filter membrane to prevent the filter membrane from rupturing.

③The pore size of the microporous filter membrane is cone-shaped, and the smooth side has a small pore size as the front side; the rough side has a large pore size as the backside. When installing, the front side should be facing down and the backside up, otherwise it is easy to be blocked by impurities and affect the filtration rate. Soaking the treated filter membrane in water for injection, if the temperature is low and soaking the drug solution for 5 to 10 minutes at the same temperature to avoid rupture caused by the drop in tensile strength of the filter membrane due to the temperature difference.

④Do not sterilize the filter holder together with the filter membrane, otherwise, the filter membrane may become brittle and crease due to thermal expansion and contraction.

⑤After use, put the microporous filter membrane in water for injection to prevent it from drying, but do not soak for too long. The microporous filter membrane that has been dehydrated and dried cannot be used.

⑥According to the concentration and viscosity of the liquid medicine, microporous membranes with different pore diameters should be selected.

⑦If you find that the microporous filter membrane has small holes or small cracks, you can rinse it with the original broken filter membrane and dry it, then tear it up and place it in a small cup with a small amount of acetone. Stir it into a paste-like mucus. On the small holes or cracks of the flat filter membrane, drop it, but never too much. Cover the mucus a little larger. You can continue to use it without affecting the use effect after it dries.