Requirements for a PAN Precursor

Acrylic precursors for the carbon fiber industry originated from companies that were established commercial scale producers of textile grade acrylic fibers. Hence, the manufacturers that could most readily adapt their existing technology to create a precursor grade material have been most successful (Table 4.2). However, some aspects such as dyeability and a tendency to yellow are not important parameters for a carbon fiber precursor but, because that particular polymer formulation was initially used for other textile end uses, the polymer composition could not be changed. As carbon fibers have developed, the market requirement for suitable precursors has increased and new polymers have been developed specifically for the manufacture of carbon fibers. 

To have a better understanding of the requirements for a PAN precursor, it is necessary to consider what properties the PAN polymer should have and what the resultant properties of the spun fiber should be. Some of the more important parameters required to produce an acceptable PAN precursor are  

A pol5mer with an acrylonitrile content less than 85%, or a homopol5mer, will not make a satisfactory PAN precursor. The choice of comonomer(s) does have a most important role in the preoxidation stage of the carbon fiber manufacturing process. 

The molecular weight and molecular weight distribution of the pol5mer have to be carefully 

The polydispersity index is of the order of 1.5-3.0 and is best determined directly, using size exclusion chromatography. 

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