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Making more carbon fibers for less

| By Tetsuo Satoh

An efficient, energy-saving process for making carbon fibers (diagram) is being developed by a collaboration team of the University of Tokyo, the Institute of Industrial Science and Technology (AIST), Toray Industries, Inc., Teijin Ltd., Toho Tenax Co. and Mitsubishi Rayon Co. The team expects to enhance the production capacity to nearly 20,000 ton/yr in a single production line — ten times higher than existing production lines — while lowering production costs and cutting CO2 emissions in half. Started in 2014, the four-year project is being supported by the Japanese Ministry of Economy, Trade and Industry under a program of the New Energy and Industrial Technology Development Organization (NEDO, Kawasaki, Japan; www.nedo.go.jp), and is being coordinated by professor Kazuro Kageyama at the University of Tokyo.

carbon fibers

The key achievements thus far are: new precursor polymers have been developed by Toray that do not require an oxidization pretreatment to impart flame-retarding properties; a direct, microwave-based carbonization technology operating at atmospheric pressure has been developed by Teijin; and a dry, very fast plasma surface-treating process that enables control of the surface properties of the carbon fibers has been developed by Teijin.

The new precursor polymers enable the production of up to 24,000 filaments to be spun per “toe” to make carbon fibers with diameters of 9–17µm, which is two times thicker that fibers made by conventional polyacrylonitrile (PAN)-based polymers. The carbonization yield is also 1.5 times higher than PAN-based fibers, says NEDO. By the end of the project, the team plans to develop a commercial production line to make fibers with “excellent” mechanical properties (tensile elasticity in the range of 240 GPa, and a 1.5% elongation — equivalent to the existing PAN-based fibers).