Carbon fiber is used in many industries including aerospace, aircraft, automotive, sports and medical equipment due to its high modulus and strength. Common precursors for producing carbon fiber include polyacrylonitrile, petroleum pitch, and regenerated cellulose. In recent years, due to concerns about environmental issues and production costs, there has been increasing emphasis on using biomass resources to produce carbon fiber rather than petroleum-based resources. Among biomass resources, lignin raw materials can be obtained from agricultural waste and pulp industry waste, showing significant cost advantages.
Lignin, as the second largest natural polymer material after cellulose, contains a large number of aromatic ring structures and can be used as a precursor for the preparation of carbon fibers. Compared with polyacrylonitrile-based carbon fibers, lignin produces The cost is reduced by more than 50%.
Methods for preparing carbon fibers from lignin include melt spinning, dry spinning, wet spinning, dry jet wet spinning and electrospinning. Lignin can be processed into carbon fibers through multiple steps, including extraction, purification, Spun, stabilized and carbonized. However, the tensile strength of lignin-based carbon fibers is only one-third that of polyacrylonitrile-based carbon fibers. Due to the nonlinear molecular structure and wide molecular weight distribution of lignin, there are some problems in preparing carbon fibers from lignin, such as poor precursor fiber quality, uneven fiber diameter, large diameter, and spinneret clogging. To produce high-quality carbon fibers from lignin, several measures have been taken to improve the spinnability of lignin, including converting lignin into linear polymers. And mix it with other resins. However, these complex processing processes inevitably increase the production cost of lignin-based carbon fibers and are not conducive to their large-scale preparation.
Carbon nanotube (CNT) fiber is a special carbon fiber material composed of multiple carbon nanotubes and has high specific strength. Compared with traditional carbon fibers, carbon nanotube fibers have better flexibility, higher electrical and thermal conductivity. Preparation methods of carbon nanotube fibers include wet spinning, array rotation and floating catalyst chemical vapor deposition (FCCVD).
In addition, post-processing is often used to improve the mechanical, electrical, and thermal properties of carbon nanotube fibers, including solvent/mechanical densification, chemical doping, metal coating, acid treatment, and purification. Currently, the most commonly used method for continuously preparing carbon nanotube fibers is FCCVD. The carbon source used in this method mainly comes from petroleum fine chemicals, such as methane, ethylene, ethanol, toluene and xylene. In order to meet the requirements of low-carbon environmental protection, the preparation of carbon nanotubes using low-carbon footprint biomass as the carbon source has become a trend in this field. Research hotspots. However, there are still great challenges in the continuous preparation of carbon nanotube fibers from biomass via FCCVD method.
Based on the above challenges, the team of Academician Zhu Meifang of the School of Materials Science and Engineering of Donghua University achieved the continuous preparation of high-performance CNT fibers in lignin through the systematic integration of solvent dispersion, high-temperature pyrolysis, catalytic synthesis and assembly. The tensile strength of the lignin-based carbon nanotube fiber is 1.33 GPa and the electrical conductivity is 1.19×105 S/m. In addition, continuous production of CNT fibers at a speed of 120 m/h can be achieved. The excellent mechanical strength and electrical conductivity of lignin-based carbon nanotube fibers will greatly expand the application fields of lignin. The relevant results were published in Nature communications under the title “Continuously processing waste lignin into high-value carbon nanotube fibers”.
Keywords:
carbon fiber lignin
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