Prediction of the Shift Factors for Viscoelastic Liquids

The shift factors are usually obtained by empirical methods that involve the horizontal translation of the isotherm representing the reduced viscoelastic functions in the time or frequency domains, in double logarithmic plots with respect to the reference isotherm. However, analysis of the components of the complex relaxation moduli in the terminal region ( 0) permits 

These equations lead to the following expression for the horizontal shift factor (2,3)  

Therefore, whenever the temperature dependence of the steady-state compliance and the zero shear rate are known, the shift factors for viscoelastic liquids can be obtained directly from Eqs. (8.25) and (8.26). 

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