Polyacrylonitrile Precursor Fibers for Conversion to High-Modulus, High-Strength Fibers. Volume II. Mass Thermal Analysis.

Mass thermal analysis is employed to identify the dominant chemical reactions that are involved in the transformation of a polyacrylanitrile PAN precursor to a graphitizable carbon fiber. The results of this study indicate that, despite its popular acceptance for many years, the mechanism that postulates intramolecular cyclization to yield a linear ladder polymer has no basis in fact. An interpretation consistent with the present results involves a series of elimination reactions, followed by intermolecular crosslinking and cyclization induced by dipole interactions between pendant nitrile groups. The chemistry of oxidative stabilization of PAN AT MODERATE TEMPERATURES PROCEEDS VIA EXTENSIVE FRAGMENTATION AND CARBOXYLATION AT SUSCEPTIBLE END GROUPS. Additional reactions that have been identified are amide formation and hydroperoxide formation as a mechanism for crosslinking through ether and carbonyl structures. Author, modified-PL