Rheological properties of mesophase pitch investigated by the Giseeler fluidity method

The Giseeler fluidity method was used to investigate the rheological properties of pitch with and without heat treatment from room temperature to 520 °C. Results show that the fluidity has a good repeatability at different temperatures under different heating rates. The fluidity of the raw pitch slowly increases from 253 to 282 °C, then increases exponentially from 282 to 311 °C near the softening temperature, and finally remains unchanged from 311 to 498 °C. This changing pattern of fluidity with temperature has also been found for heat-treated mesophase pitch and can be formulated by the Arrhenius equation, from which the viscous flow activation energy can be obtained. The toluene-insoluble fraction increases from 67.3 to 88.7% with heat-treatment time and the flow activation energy of the treated mesophase pitch in the Newtonian fluid region at low temperature range is between 203.6 and 294 kJ/mol.