Rheological properties of coal tar pitches containing micronic graphite powders Original Research Article

The viscosity of coal-tar pitch (CTP) mixtures with pulverulent graphite was determined between 100 and 180 °C. The pitch precursor viscosity dependence on temperature obeys an equation proposed by Williams, Landel and Ferry (WLF equation), whose coefficients could be qualitatively related to the chemical composition. The addition of graphite particles in the pitch matrix leads to the apparition of a non-Newtonian behaviour and to an increase of the dispersion viscosity. Changes in rheological characteristics are mostly related to the graphite particle morphology; they are dependent, to a lower extent, on the chemical composition of the pitch matrix. By using the Einstein equation to describe the changes in viscosity with the graphite volumic fraction, adsorption of the heaviest pitch molecules at the surface of the graphite particles is postulated.