The effect of the substrate on pitch wetting behaviour

The wetting behaviour of a petroleum pitch (modified with a surfactant) and a binder coal-tar pitch was studied using different substrates. The results show that both the pitch and the substrate have a significant influence on wetting behaviour, and consequently, on their mutual interactions during the mixing stage. Low values of surface tension and viscosity in the pitches lead to lower wetting temperatures. It was found that with petroleum coke and magnesia as substrates, the wetting occurs at lower temperatures than with graphite and carbon black for all pitches. Moreover, experiments carried out with amorphous and crystalline alumina revealed that the crystalline order affects the wetting behaviour considerably. Thus, whereas the pitch wets the corundum (crystallized alumina), it does not wet the amorphous alumina (basic, acid and neutral alumina)