Liquid Viscosity Near Glass Transition Temperature
I. Derivation of Doolittle Equation for Liquid Viscosity and Its Relation to Andrade Equation
1962 Volume 19 Issue 204 Pages 191-196
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1962 Volume 19 Issue 204 Pages 191-196
The Doolittle equation for liquid viscosity, In η=A+B/f, is proved on the basis of a simple equation of state of liquids and of a molecular model for viscous flow process. The meanings of the constants A and B are elucidated. A is expected to be about -8.0 for normal liquids and B is a constant very near to unity and becomes abnormally small for molten metals.
A function C(T)=-(∂ In Pi/∂ In T) p (contraction function) is introduced to represent the temperature dependence of internal pressure. When C (T)=0, the Doolittle equation is reduced to Andrade equation, In η=AA+Evis/RT, where AA=A and B=Evis αι/R≈1 (αι the expansion coefficient).
