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Under what circumstances can PTFE filter membrane become hydrophilic without surface modification?

Issuing time:2023-10-23 09:20

Polytetrafluoroethylene (PTFE) is hydrophobic in nature, meaning it repels water. This property is attributed to the structure of PTFE, which is composed of carbon atoms completely surrounded by fluorine atoms. The strong bond creates a protective barrier that prevents other substances, including water, from interacting with the material.

Hydrophilicity of PTFE filter membrane.jpg

Therefore, in actual applications, it is necessary to use a modification process to treat the PTFE membrane in order to make it hydrophilic or partially hydrophilic. In this process, the surface of PTFE has been chemically modified to produce PTFE membranes on its surface. New functional groups or chains are usually accomplished through a process of graft polymerization, in which monomers are chemically bonded to the surface of PTFE to form graft chains. With the goal of making PTFE hydrophilic, polymers can be added that can interact with water. Polar functional groups in molecules that form hydrogen bonds.

surface modification of membrane.png

Similarly, in processes such as plasma treatment and radiation grafting, plasma treatment uses ionized gas (plasma) to modify the PTFE surface. The high-energy particles in the plasma can destroy some carbon-fluorine bonds on the surface and form new functional groups. , can react with other substances such as water (when made hydrophilic). The main function of this type of process is to destroy the original molecular structure of polytetrafluoroethylene and use chemical reactions and other processes to break the barrier between carbon atoms and fluorine atoms to make it hydrophilic. In these methods, PTFE is used on the surface. Modifications have occurred at the molecular level, but most of the bulk materials remain unchanged, retaining many of their original properties, such as chemical inertness and thermal stability.

molecular structure of PTFE membrane.jpg

From the above analysis, it can be seen that in order to change the hydrophilicity of the PTFE membrane, we must start by changing its internal molecular structure, and changing the structure requires chemical or special modification methods to achieve the hydrophilic effect. That is, PTFE does not naturally become hydrophilic without any form of surface modification, at least under existing process conditions, so in order to make PTFE hydrophilic (water absorbent), it must be changed its surface properties.

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