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 t o modify pitch properties for composite preparation. Two commercial co al-tar pitches, an impregnating pitch and a binder pitch, were air-blo wn at temperatures between 250-300 degrees C, for 18 and 14 h, respect ively, to produce pitches of similar softening point ranging from 148 to 223 degrees C. Parent and treated pitches were characterized by ele mental analysis, FTIR, thermal analysis (TMA, TGA, and DTA), solubilit y in toluene and quinoline, XPS, X-ray diffraction, and optical micros copy. Additionally, parent pitches were also characterized by extrogra phy. Pyrolysis products of parent and treated pitches, obtained at 450 degrees C, were characterized by optical microscopy to monitor the in fluence 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 impreg nation. During air-blowing, the reactions of dehydrogenative polymeriz ation and crossing-linking of oligomers occur.