Determination of viscoelastic properties of pitches by torsional creep

✍ Scribed by Mototsugu Sakai; Michio Inagaki

• Publisher: Elsevier Science
• Year: 1981
• Tongue: English
• Weight: 715 KB
• Volume: 19
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(81)90102-0

✦ Synopsis

Creep behavior of a petroleum pitch and of two kinds of coal tar pitch, as they are and as mixed in various portions, were studied by measuring the torsional creep at temperatures of 3040°C. The pitches used were viscoelastic, and viscous and elastic terms were separately evaluated from the steady state viscosity 11 and the steady state creep compliance Jz. The viscosity shows a negative temperature dependence, from which the activation energy for steady state flow is found as 63 kcal/mol for all pitches used. The compliance Ji increases with increase in temperature. This indicates the importance of inter-and intra-molecular potential energy in the elasticity of pitch. A time-temperature superposition rule was found to be satisfactorily applicable to the creep data observed. A rheological meaning of the softening point of pitch is discussed, and the importance of differences in steady state creep compliance is emphasized. Viscoelastic analysis was found to be useful in giving important parameters for the characterization of pitch-like materials.