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What is the silanization process for surface modification of filter membranes?

Issuing time:2023-11-10 15:43

Silanization method is a commonly used surface modification technology for filter membranes. It is a chemical reaction between the surface substance of the filter membrane and the silylating agent. The silyl groups after the reaction are attached to the membrane surface, thereby imparting the filter membrane with Special properties, such as chemical stability, hydrophobicity, hydrophilicity, etc. The silylating agent mentioned here is a compound that usually contains one or more silyl groups. The silicon atoms (Si) bonded to the organic substituent (R group) form a functional group that can interact with the membrane surface. Specific functional groups, such as the most common hydroxyl (-OH) functional group and amino (-NH2) functional group, react, and the silyl group replaces the active hydrogen atoms in the functional group, forming a covalent bond between the silylating agent and the membrane surface. bond, this silanization reaction will form a single layer of silyl groups on the membrane surface, thereby changing the properties of the membrane surface.

Membrane silanization, silanization membrane filter, microporous membrane modification principle.jpg

Most commonly used silylating agents are organosilanes. Depending on the application, different functional groups can be selected based on the requirements of the film properties, such as trimethylchlorosilane (TMCS), which can react with hydroxyl groups (-OH) on the surface. reaction, replacing it with methyl group (-CH3); hexamethyldisilazane (HMDS), which can react with the hydroxyl group on the surface, replacing it with trimethylsilyl group (-Si(CH3)3 ); Octadecyltrichlorosilane (OTS), used to introduce long hydrocarbon chains on the membrane surface to react with hydroxyl groups, replacing them with octadecyl (-C18H37); Aminopropyltriethoxysilane (APTES) , which can react with the amino group (-NH2) of various functional groups on the membrane surface (including hydroxyl and carboxyl groups).

The main process steps include:

1. Cleaning and activation. Before surface modification, first clean the filter membrane surface to remove impurities and activate all possible reactive groups on the surface. Usually some solvents, strong chemicals (such as acids, alkalis or oxidants), or plasma are used. Processing etc.

2. Silanization reaction, and then add silane to the cleaned and activated membrane surface. Silane is usually dissolved in alcohol, water, hydrochloric acid or amine and other solvents, and reacts with the filter membrane surface to achieve silanization.

3. Post-treatment, after the silanization reaction, perform a cleaning and drying step, clean the surface to remove any residual silane or reactants and dry it.

The silanization method provides multiple advantages for surface modification of filter membranes. It can enhance the hydrophobicity or hydrophilicity of the membrane surface, chemical resistance, reduce fouling, or provide specific functions for the target application. However, due to its process The technical requirements for precise control are relatively high, and the production cost is also expensive compared to other processes.

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