Rheological Properties of Modified Coal Tar Pitches

Abstract

Different modifiers composed of polyethylene glycol, paraformaldehyde, polystyrene, and polyphosphoric acid at different ratios (designated CD-0, CD-1, CD-2. CD-3, and CD-4) were added to coal tar pitch. The resulting modified pitches were prepared and designated control D-0 and D-1, D-2, D-3, and D-4, correspondingly. The objective of this study was to evaluate the properties of the control and modified coal tar pitches by the dynamic shear rheometer (DSR) test and microscopic imaging technology. The complex shear modulus G* and phase angle δ of the modified coal tar pitches decreased with increased temperature, which indicated a decline in the gradual capacity for resistance to permanent deformation at high temperatures. There was good correlation between the Christensen-Andersen-Marasteanu (CAM) model and the complex modulus master curve of the modified coal tar pitches. The test results showed that D-4 had a higher complex viscosity η* than that of the control D-0 and the other modified coal tar pitches (D-1, D-2, and D-3), along with a higher glassy complex modulus Gg*, cross frequency fc, rheological parameter r, and better resistance to rheological deformation. Control D-4 also had a strong capability to resist high-temperature permanent deformation. In addition, the homogeneity of D-4 was better than that of the control D-0 and the other modified pitches, as observed in microscopic images. Therefore, it could be concluded that D-4 had better properties compared with the others.