Study of the Isakovich—Chaban Theory in Viscoelastic Relaxation

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Abstract
The recently proposed Isakovich—Chaban phenomenological theory for highly viscous liquids is examined, as it relates to the complex shear modulus for viscoelastic liquids, in the light of experimentation over the sonic frequency regime of liquid relaxation. Two butanediols, glycerol, and two chlorinated biphenyls are studied experimentally at atmospheric pressure to compare shear‐relaxation spectra at various temperatures with the theoretical predictions. Similar comparison is made for one of the biphenyls at two temperatures but over a range of static pressure variation. Experimental spectra for polyisobutylene at atmospheric pressure are presented (reduced to a single temperature) to estimate applicability of the theory to polymeric materials. The findings generally indicate very good agreement between theory and experiment, except in a few instances for liquid shear rigidity over the upper frequency portion of the spectrum and for the maximum imaginary modulus component. Isakovich—Chaban theory does not appear to represent quite as well experimental results taken under static pressure variation at elevated temperature as it predicts relaxation spectra under temperature variation at ambient pressure. The theory may relate to certain polymers as well as to liquids, at least judging from the excellent comparison realized in the case of polyisobutylene at atmospheric pressure, where the analytical method even describes qualitatively the low‐frequency behavior observed by other investigators.