XPS studies on the chemical structure of the stabilized polyacrylonitrile fiber in the carbon fiber production process

Abstract In the carbon fiber production process from polyacrylonitrile (PAN), PAN precursor is heated first in air to secure stabilization in the succeeding carbonization process at higher temperature. The mechanism of the stabilization reaction and chemical structure of the stabilized PAN have been examined by x‐ray photoelectron spectroscopy and elemental analysis. The stabilized PAN was determined to have a ladderlike structure consisting of 40% acridone ring, 30% naphtyridine ring, 20% hydronaphtyridine ring, and others. This structure well explains the stability of the polymer in the succeeding carbonization process on carbon fiber production with conjugated π‐electron systems over the whole polymer chain and intermolecular hydrogen bonds. A comonomer addition to the precursor was found to accelerate the dehydrogenation reaction in the stabilization process.