MODIFICATION OF COAL-TAR PITCH BY AIR-BLOWING .2. INFLUENCE ON COKE STRUCTURE AND PROPERTIES

This study is concerned with the use of air-brewing to improve pitch p roperties as matrix precursor of carbon-carbon composites. Two commerc ial coal-tar pitches, an impregnating pitch and a binder pitch, and th eir air-blown products obtained at temperatures between 250 and 300 de grees C, were pyrolyzed in a horizontal tube furnace at 1000 degrees C . Cokes were characterized by light microscopy to monitor the influenc e of air-blowing on their optical texture. Density and porosity of cok es were determined by helium densimetry and mercury porosimetry, and t heir strength and reactivity by a microstrength test and thermogravime tric analysis, respectively. Results show that air-blowing of the impr egnating pitch produces a decrease of the optical texture of coke, whi le in the case of the binder pitch there is an improvement of the micr ocrystalline structure. Moreover, air-blowing brings about a substanti al increase in the density and strength of cokes, and a decrease in th eir porosity and reactivity.