Graphite carbon fibers rayon precursor processing

The overwhelming success of PAN-based carbon fibers over rayon and pitch can be attributed to several key aspects.f Structurally, PAN has a faster rate of pyrolysis without much disturbance to its basic structure and to the preferred orientation of the molecular chains along the fiber axis present in the original fiber. By contrast, carbon fibers from rayon suffer from extremely low carbon yield (20-25%) due to chain fragmentation, which eliminates the orientation of the precursor fiber. While improved properties can be achieved by stretch graphitization, this process is expensive and does not compensate for the low yields. 

Several books and reviews have been published which detail the conversion of viscose rayon to carbon fibers [1-7], Chapter 3 has described how carbon fiber first came onto the scene, way back in 1880, with the introduction of Thomas Edison s electric lamp filaments made from cellulosic precursors. Almost 80 years later, in 1959, the National Carbon Company (a division of Union Carbide) introduced a carbon cloth from a rayon precursor, to be followed by a carbon yarn in 1961. These products are described by Cranch [8]. The best grade on offer was WYB cloth, which was processed at 2200°C and although called graphite, was a form of carbon that was non-graphitizing. 

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