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Filtration, separation and purification

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Filtration Solutions for Carbon Fiber Production

Carbon fibers consist of carbon atoms held together to form a long chain, which is very hard, strong and lightweight, while it can be used in many processes to make excellent building materials. The raw materials used to make carbon fibers are called precursors. About 90% of carbon fiber is made of polyacrylonitrile (PAN). The remaining 10% is made of rayon or petroleum pitch. In the manufacturing process, a variety of gases and liquids are used, designed to react with the fibers to achieve specific effects.

002 lattice fringe images of nanofibers with different nanotexture.Figure.1 002 lattice fringe images of nanofibers with different nanotexture. (Inagaki M, et al. 2013)

Generally, the manufacture of PAN-based carbon fibers is carried out in three main steps. The first step is to spin the PAN polymer solution to make PAN precursor fibers. The second step is to stabilize (cyclize and oxidize) PAN precursor fibers by heat treatment (<300 ℃). The final step carbonizes the fiber (up to 1500 ℃), removes all non-carbon atoms, and produces the final product, which is carbon fiber.

Alfa Chemistry provides customers with excellent filtration solutions for the purification of PAN precursors and carbon fiber production. Our advanced carbon fiber production process filtration solutions can effectively trap impurities, providing the highest quality PAN precursors and spun fibers for small and large carbon fiber tows.

Raw Material Filtration

The particulate matter present in the PAN precursor has a direct effect on weakening the carbon fiber. All monomers, comonomers, softened water, initiators, additives, and other streams need to be filtered to the sub-micron level before entering the reactor. This ultra-fine filtration usually requires multiple stages of filtration to effectively manage the particle load to extend the life of the final critical filter.

Alfa Chemistry offers the largest product portfolio and numerous options to effectively optimize the filtration of each feed stream, such as depth filters made of polyphenylene sulfide (PPS) media. It has an absolute rated downstream part and a proprietary depth structure of the upstream part of the continuous profile aperture. Simultaneously, the PPS medium is chemically inert and can be used in corrosive environments.

Solvent Filtration

Proper solvent filtration is essential to avoid pollution during the carbon fiber production process. Our solvent filter is an ideal choice for DMSO or DMAc solvent filtration. It uses different pore sizes and ultra-fine fiber diameters to effectively remove contaminants in the solvent with a very low-pressure drop. By using more pores, the filter system extends the life of the filter and reduces the frequency of expensive maintenance interventions.

Solvent Filtration

Dope Filtration

Elimination of gels from dope prior to spinning is essential to obtain carbon fibers with the highest quality and tensile strength. The coating filtration solution uses a continuous polymer filtration (CPF) system. The metal discs and candles are made of hard sintered true random fiber media with tapered hole geometry to maximize the capture of gels and particles.

In addition, CPF technology with a diverter valve facilitates smooth filter replacement without pressure peaks, thereby ensuring continuous operation and minimizing downtime. The superior pollutant capture of this filter system uses smaller diameter precursors, which increases the chances of stability and promotes optimal process efficiency.

If you are looking for innovative carbon fiber production filtration solutions, you have come to the right place. Our knowledgeable subject matter experts are at your service. Contact us for more information, we look forward to assisting you soon.


  1. Inagaki M, et al. (2013). "Chapter 2.1 - Advanced Carbon Materials." Handbook of Advanced Ceramics (Second Edition). Materials, Applications, Processing, and Properties: 25-60.

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