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Production of Polyacrylonitrile (PAN) Precursor for Carbon Fibers: Measurement of Solvent Concentration ((Dimethyl Sulfoxide (DMSO), Dimethyl Formamide (DMF) And Dimethyl Acetate (DMAC))

PAN-based carbon fiber is widely used in many industries such as automotive, aviation, aerospace, sporting goods, and construction applications, as carbon fibers have several advantages including high stiffness, high tensile strength, low weight, high chemical resistance, high temperature tolerance and low thermal expansion. The demand has prompted as industries are looking for solutions that save energy, make more durable products and are environmentally friendly.

Carbon fiber is a long, thin strand of material that contains over 90 % of carbon by weight. Carbon fibers are obtained by pyrolysis of an appropriate precursor fiber. 
Polyacrylonitrile (PAN) is the predominant precursor for carbon fiber due to a superior strength and stability, and higher carbon yield. About 90 % of the carbon fiber produced is made from PAN and the remaining 10 % is made from rayon or petroleum pitch.

The first step in the production of PAN-based carbon fibers is spinning the PAN co-polymer to form the fibers. Because PAN decomposes before melting, it is necessary to make a spinning solution or dope solution with a solvent to be able to spin the material into a fiber. Common solvents are dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), dimethyl acetate (DMAc) and sodium thiocyanate. The concentration of the dope solution is usually 15-25 wt-% and should be carefully controlled to ensure its ability to form filaments of high mechanical strength. 

The K-Patents Process Refractometer PR-43-GP is installed in-line to monitor the concentration of solvent at different stages of the process. The K-Patents Process Refractometer provides real-time information to keep the concentration at its optimum level. Many carbon fiber companies have vertically integrated manufacturing and make each product in their supply chain, starting from PAN precursors to final composite and finished parts. These are e.g. Toray, Mitsubishi Rayon, Formosa Plastics, SGL, Hexcel, Cytec, Dow, Hyosung, RIL and Taekwang.

Application Note ref. 10.02.04 Production of Polyacrylonitrile (PAN) Precursor for Carbon Fibers (PDF)

Learn more about the K-Patents refractometers in Fiber and textiles production on the application page