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What are the main differences between composite microporous membranes and pure membranes in terms of

Issuing time:2024-05-14 14:57

Composite membranes and pure membranes both belong to the membrane category, but they also have essential differences. A composite membrane is a membrane composed of multiple layers or materials with different functions. These layers are combined to form a membrane with enhanced properties or special requirements. Characteristics, such as hydrophilic, hydrophobic, anti-corrosion, etc., with a porous support layer that provides mechanical strength and a selective layer with specific separation, filtration or permeability properties. The structural advantage of composites is that it allows the individual properties to be optimized by using different materials in different layers. A pure membrane, also known as a homogeneous membrane, is a membrane made of a single material. It has no additional layers or additives. Its manufacturing method is also formed by a single-step process, which has the ability to form a porous structure. The pure membrane has a unique structure throughout the membrane structure. Material compositions are homogeneous and they exhibit specific properties inherent to the material used, such as chemical resistance, selectivity or permeability, etc.

Composite membrane and pure membrane

The manufacturing methods of composite membranes and pure membranes are different due to different properties.

The production method of composite microporous membrane includes:

1. Interfacial polymerization method, which is to dissolve two or more monomers or polymers in separate solvents. The solutions contact at the interface and a chemical reaction occurs, thereby forming a thin selective film layer on the support layer.

2. The method of coating or solution casting mainly involves coating or impregnating the preformed porous support layer with a solution containing the desired selective material, and then drying or solidifying the solution, which will form a thin selection on the carrier. sexual membrane layer.

3. Layer-by-layer assembly method, which deposits alternating layers of different materials onto the support layer. The material used as the support layer can be made using methods such as dip coating, spray coating or spin coating. The advantage of the layer-by-layer assembly method is that it can be accurately Control membrane structure and properties.

4. Electrospinning method, which is a method of electrostatically drawing a polymer solution or melt into thin fibers to form a film layer of a non-woven mat. The electrospun fibers can be layered or combined with other materials to form Composite membranes with specific properties.

composite membrane production process

Pure membrane production methods include:

1. Phase inversion method. Phase inversion is a common method for producing pure membranes, which is to dissolve the polymer in a solvent, and then form the polymer through controlled cooling, immersion in a non-solvent or evaporation, causing phase separation of the solvent, thereby Form a membrane with a porous structure.

2. Mechanical stretching or orientation, a method of producing polymer films or sheets by stretching or orienting them. This process aligns the polymer chains to form a porous structure with specific properties. Of course, the stretching method can be customized according to needs. Uniaxial or biaxial stretching can be performed to effectively control the pore size and structure according to actual needs.

3. Track etching method. Track etching is a technology that uses high-energy particles to impact the surface of a polymer film to form tracks or channels. This method can selectively etch tracks to form holes. This production method can It is a very precise membrane production technology that precisely controls the pore size and has uniform pore size and optional shapes.

4. Solvent casting method. Solvent casting is to dissolve the polymer in a solvent to form a solution or dispersion, and then cast the solution onto a substrate or support and dry it to form a solid film with a porous structure.

process characteristics of pure membrane

In production applications, composite membranes and pure membranes are often used in applications requiring different combinations of properties. They can be used in fields such as water treatment, gas separation, biotechnology and pharmaceuticals. For example, they can be used in nanofiltration or reverse osmosis processes to achieve high selectivity and retention of specific solutes; pure membranes are usually used where specific performance is required. , PVDF or PES (polyethersulfone) membranes, etc., pure polymer membranes are used in microfiltration or ultrafiltration processes for effective separation of particles or biomolecules without the need for additional functionality.

The specific choice between composite microporous membranes and pure membranes depends on the desired performance and application requirements, as both types of membranes have their advantages and can be customized with different production methods or processes to meet specific filtration requirements. and separation needs.

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