PREPARATION OF ISOTROPIC PITCH PRECURSORS FOR GENERAL-PURPOSE CARBON-FIBERS (GPCF) BY AIR BLOWING .2. AIR BLOWING OF COAL-TAR, HYDROGENATEDCOAL-TAR, AND PETROLEUM PITCHES

Three representative isotropic pitches. coal tar pitch NP80. its hydro genated NHP, and petroleum pitch A60, were air blown at 330-degrees-C in order to study comparatively their oxidation reactivities in the pr eparation of isotropic pitch precursors with a high softening point. T hey showed different oxidation behaviors during air blowing. Coal tar pitch with a low softening point of 80-degrees-C showed the most rapid rise of softening point but suffered the smallest pitch yield. Air-bl own coal tar pitches, NP80-1 and NHP-1, exhibited a higher degree of a romatic condensation and larger QI content than the petroleum one even when their softening points were around 280-degrees-C. The structure characterization of the parent and air-blown pitches by FT-IR. FD-mass , and solution H-1-, C-13-NMR suggests the mechanism of air blowing to raise the softening point. Unexpectedly slow rises in softening point s of hydrogenated coal tar and petroleum pitches appear to be ascribed to their alkyl and naphthenic groups. which may terminate the chain r eaction of oxidation.