Precursors for Carbon Fiber Manufacture

Since the early work of Edison, many types of precursors have been used to produce carbon fibers, of which polyacrylonitrile (PAN) has proved to be the most popular. 

The ideal requirements for a precursor are that it should be easily converted to carbon fiber, give a high carbon yield and allow to be processed economically. The attraction of PAN is that the polymer has a continuous carbon backbone and the nitrile groups are ideally placed for cyclization reaction to occur, producing a ladder polymer, believed to be the first stage towards the carbon structure of the final fiber. 

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The homopolymer PAN is not an easy product to process into carbon fiber, since the initial oxidation stage of the carbon fiber process is a difficult reaction to control due to the sudden and rapid evolution of heat, coupled with a relatively high initiation temperature. This rapid surge of heat can cause chain scission with resultant poor carbon fiber properties. As far as is known, homopolymer PAN has never been exploited as a precursor for carbon fiber manufacture. The exothermic reaction can, however, be adequately controlled by suitable comonomers such as itaconic acid. 

PRECURSORS FOR CARBON FIBER MANUFACTURE AN comonomers + water... 

A copolymer must have acrylonitrile content greater than 85%, preferably 90-95%. To the author s knowledge, no commercial exploitation has been made of homopolymer PAN as a precursor for carbon fiber manufacture. 

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