Fiber Production using a Cellulosic based Precursor

CARBON FIBER PRODUCTION USING A CELLULOSIC BASED PRECURSOR... 

The precursor fiber type for reinforcing the carbon matrix can be an oxidized PAN fiber (opf), or either a PAN or pitch based carbon fiber. In some instances, for special applications, such as the Shuttle, a cellulose based carbon fiber is used. The reinforcements can be unidirectional have a random chopped fiber presentation as in a felt format a woven product from continuous fiber presented in a 2D, 3D, or in a Multi-D format (Section 21.1), or a non-woven carbon fiber. The chosen fiber architecture is most important for a given application and Lei et al [4] describe how, for example, 3-D braiding can be applied to carbon-carbon composites. One of the early forms of near net shape reinforcement used for carbon-carbon aircraft brakes was based on a weft knitted 3-D fabric made by the Pressure Foot process (Figure 14.1). 

Union Carbide, Danbury, CT, USA—pioneered the use of cellulosic precursors to make Thornel carbon fibers and entered the market in 1965 but, unfortunately, had to resort to hot stretching to obtain properties to be able to compete with PAN based products. In 1973, started the manufacture of carbon fibers from a pitch base. Entered into a technical licensing agreement with Toray in 1978 to produce carbon fiber in the USA based on Toray s PAN technology. The carbon fiber facility was acquired by Amoco and the carbon fibers are distributed by EMI Composites in the UK. 

Much less ordered than PAN-based high-strength CFs are the isotropic CFs. They are produced by the carbonization of isotropic pitch fibers (or other fibrous precursors such as phenolic resins or cellulose, including rayon), without any attempt to obtain a preferred orientation of the polyaromatic molecules in the fiber direction. Consequently, they have a random nanotexture and belong to the low modulus class of CFs [16]. Rather than being used for high-performance reinforcement purposes, they find their application as thermal insulators for furnaces or as reinforcements for cement [1]. Another important use of isotropic CFs is as a feedstock for the production of activated carbon fibers, a material dealt with in Section 2.4.4. 

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