An insight into pitch/substrate wetting behaviour. The effect of the substrate processing temperature on pitch wetting capacity

Pitch/substrate interactions at the mixing stage (<200 °C) were studied by means of a drop spreading wetting test. The substrates were obtained from a petroleum pitch by thermal treatment in the temperature range of 300–1900 °C. The results show that thermal treatment has a significant influence on the physical and chemical properties of the substrates, and consequently, on pitch/substrate wetting behaviour. Substrates with plastic properties (softening point below 350 °C) deform and/or agglomerate during the wetting experiment and thereby stop pitch penetrating. Moreover, the presence of aliphatic hydrogen in these substrates facilitates oxidative stabilization, which in turn facilitates pitch/substrate wetting behaviour. Substrates obtained above 400 °C are wetted by the pitch. However, the pre-graphitic order obtained on carbonization does not seem to have a significant effect on pitch wetting capability under the conditions used in this study. The oxidative stabilization of the substrates does not exert a significant influence on unfused substrates. However, in the case of plastic substrates, pitch wetting capacity is greatly affected by oxidation.