MODIFICATION OF COAL-TAR PITCH BY AIR-BLOWING .1. VARIATION OF PITCH COMPOSITION AND PROPERTIES

Pitch oxidation by air-blowing has been studied as a possible method to modify pitch properties for composite preparation. Two commercial coal-tar pitches, an impregnating pitch and a binder pitch, were air-blown at temperatures between 250-300 degrees C, for 18 and 14 h, respectively, to produce pitches of similar softening point ranging from 148 to 223 degrees C. Parent and treated pitches were characterized by elemental analysis, FTIR, thermal analysis (TMA, TGA, and DTA), solubility in toluene and quinoline, XPS, X-ray diffraction, and optical microscopy. Additionally, parent pitches were also characterized by extrography. Pyrolysis products of parent and treated pitches, obtained at 450 degrees C, were characterized by optical microscopy to monitor the influence of air-blowing on mesophase formation. Results show that pitch modification by air-blowing produces a significant increase in carbon yield, without restricting the fluidity necessary to pitch for impregnation. During air-blowing, the reactions of dehydrogenative polymerization and crossing-linking of oligomers occur.