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Should I choose a mechanical biaxially stretched membrane or a chemical phase separation membrane?

Issuing time:2023-05-16 14:06

The biaxial mechanical stretching process involves stretching polymer membranes in both the CD and MD directions. This process can produce membranes with a well-defined pore structure and good mechanical strength, however, the precision of the pore size distribution may be limited by the stretching process, since the precision of mechanically stretched membranes is usually measured in terms of pore size and pore size distribution. Pore sizes can vary from a few microns to tens of nanometers, depending on the material and stretching process, and achieving very small and uniform pore sizes can be challenging.


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The filter membrane produced by mechanical stretching, the more commonly used materials are:
1. Polypropylene (PP), a popular choice due to its excellent chemical resistance, hydrophobicity and mechanical strength. Widely used in water treatment, food and beverage, pharmaceutical and other industries.
2. Polyethylene (PE), another commonly used material for mechanically stretched membranes. It has good chemical resistance, hydrophobicity and flexibility. It is commonly used in gas separation and water treatment applications.
3. Polytetrafluoroethylene (PTFE), which is known for its excellent chemical resistance, hydrophobicity and temperature stability. It is commonly used in applications requiring high chemical resistance and temperature stability, such as chemical processing and gas filtration.
4. Polyvinylidene fluoride (PVDF), is a multifunctional material with good chemical resistance, hydrophobicity and mechanical strength. It is used in a variety of industries including water treatment, pharmaceuticals and biotechnology.

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The chemical phase separation process involves the formation of porous structures by controlled precipitation of polymer solutions. Depending on the choice of polymer, solvent, and precipitation conditions, this process can produce membranes with various pore sizes and morphologies. Chemical phase separation processes generally offer better precision in pore size control and distribution, as well as the ability to achieve smaller pore sizes. Filtration membranes produced by phase separation processes generally have higher precision than mechanically stretched membranes. This is because the phase separation process allows better control over pore size and pore size distribution.
Filtration membranes produced by phase separation processes are typically made from a variety of materials, depending on the desired properties and application requirements. Some common materials include:
1. Polyethersulfone (PES): PES is known for its excellent mechanical strength, chemical resistance and hydrophilicity. It is widely used in biotechnology, pharmaceutical and water treatment applications.
2. Polysulfone (PS): Polysulfone has good mechanical strength, chemical resistance and thermal stability. Commonly used in water treatment, food and beverage, pharmaceutical and other industries.
3. Polyvinylidene Fluoride (PVDF): PVDF is a multifunctional material with good chemical resistance, hydrophobicity and mechanical strength. It is used in a variety of industries including water treatment, pharmaceuticals and biotechnology.
4. Cellulose acetate (CA): Cellulose acetate is a biodegradable and renewable material with good hydrophilicity and chemical resistance. It is commonly used in water treatment, especially reverse osmosis and nanofiltration applications.
5. Polyamide (PA): Polyamide membranes are commonly used in reverse osmosis and nanofiltration processes due to their excellent chemical resistance, hydrophilicity and selectivity.

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In a word, in the direction of filter membrane selection, if precision and pore size control are your most concerned issues, then the chemical phase separation process may be a better choice. On the contrary, if you put aside the precision and pore size and just focus on mechanical strength, production cost and scalability, then the filter membrane produced by mechanical biaxial stretching is your best choice. However, for membrane products at the present stage, in order to not only ensure the accuracy of the product, but also use the membrane product to have a certain strength, it is relatively common to combine the two processes, but this factor requires you to put aside the cost. The selection of filter membrane must be combined with specific application requirements, comprehensive analysis and testing, close cooperation between engineering and R&D teams, and professionalism and cooperation of suppliers. This is a relatively long process.


Citation

1.Mulder, M. (1996).Basic Principles of Membrane Technology (2nd ed.). Springer.https://doi.org/10.1007/978-94-009-1766-8

2.Baker, R. W.(2012). Membrane Technology and Applications (3rd ed.). John Wiley & Sons.https://doi.org/10.1002/9781118359686

3.Loeb, S., &Sourirajan, S. (1963). Sea Water Demineralization by Means of an OsmoticMembrane. Advances in Chemistry, 38, 117-132.https://doi.org/10.1021/ba-1963-0038.ch011

4.Strathmann, H.(2011). The Formation Mechanism of Phase Inversion Membranes. Desalination,277(1-3), 3-20. https://doi.org/10.1016/j.desal.2011.04.068

5.Van der Bruggen,B., & Vandecasteele, C. (2003). Distillation vs. Membrane Filtration:Overview of Process Evolutions in Seawater Desalination. Desalination, 143(3),207-218. https://doi.org/10.1016/S0011-9164(02)00259-X


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