Carbon/carbon composites with heat-treated pitches: I. Effect of treatment in air on the physical characteristics of coal tar pitches and the carbon matrix derived therefrom

Abstract

Coal tar pitch has been heat treated at 350°C in the presence of air and nitrogen for different times. The treatment temperatures have been pre-estimated from the behaviour of pitch during heat treatment in the presence of air. The modified pitches so obtained have been characterised by FTIR, TGA, DTG, DSC, elemental analysis, etc. FTIR studies reveal that the aromaticity of the pitches increases with heat treatment in air at 350°C up to 5 h. TGA studies also exhibit characteristic differences in pyrolysis behaviour of these pitches. C/H ratio and the coke yield have been found to initially increase with treatment time but decrease with longer heat treatment. Comparison of thermal analysis data, C/H ratio and FTIR studies show that during heat treatment of pitch in air, polymerization dominates volatilization of low molecular weight compounds in the pitch.