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Viscosity/temperature equations for coal tar pitches and refined tars

1965; Wiley; Volume: 15; Issue: 9 Linguagem: Inglês

10.1002/jctb.5010150908

1934-998X

L. J. Wood, M. C. Downer,

Material Properties and Processing

Abstract The viscosities of eighteen tar products ranging from refined tar of 34° equiviscous temperature to electrode binder pitch of 102° softening point (Ring Ball) have been measured between wide temperature limits and within the viscosity range of 10 to 10 10 centipoises. The applicability of three equation forms to these results has been assessed. A simple logarithmic relationship in terms of Fahrenheit temperature is satisfactory for most products at viscosities greater than 10 4 centipoises, but does not apply at lower viscosities or to the harder pitches. A double logarithmic viscosity/temperature relationship fits the results well, except those relating to the hard pitches, but it is insensitive and unreliable at viscosities of about 10 9 centipoises and greater. A third equation relating the logarithm of viscosity to the fifth power of absolute temperature has been shown to apply over the full range of materials, temperatures and viscosities examined. The significance of the constants used in these equations is discussed with respect to their value in comparing the temperature susceptibility of tar products. It is shown that the correct order of viscosity of a tar product, within the range of materials and viscosities investigated, can be predicted from its softening point or equiviscous temperature and its toluene‐insoluble content.