Characterization of Air Blown Pitches with ESR

Abstract

Reactions of coal tar and petroleum pitches with air blowing process for carbon fiber precursorswere investigated. Air and nitrogen blown pitches were divided into several fractionswith solvent extraction. The fractions were characterized with electron spin resonance (ESR).Structural features of the pitches were well represented by the ESR parameters, such as spinconcentration (Ns), shapes of spectra, and peak-to-peak linewidth (ΔHpp) which had good relationshipswith molecular weight, the size of condensed aromatic ring, and hydrogen contents.It is supposed that coal tar pitch was much sensitive to air blowing process rather than that ofpetroleum pitch. Development of polycondenced structure at the stage of mesophase transformationwas restricted in the air blowing process.