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 properties as matrix precursor of carbon-carbon composites. Two commercial coal-tar pitches, an impregnating pitch and a binder pitch, and their air-blown products obtained at temperatures between 250 and 300 degrees C, were pyrolyzed in a horizontal tube furnace at 1000 degrees C. Cokes were characterized by light microscopy to monitor the influence of air-blowing on their optical texture. Density and porosity of cokes were determined by helium densimetry and mercury porosimetry, and their strength and reactivity by a microstrength test and thermogravimetric analysis, respectively. Results show that air-blowing of the impregnating pitch produces a decrease of the optical texture of coke, while in the case of the binder pitch there is an improvement of the microcrystalline structure. Moreover, air-blowing brings about a substantial increase in the density and strength of cokes, and a decrease in their porosity and reactivity.