| Popis: |
The Vogel-Fulcher equation lnτ ∞ H/R(T-T2), and the WLF equation, lnτ a ∞ −C1(T-To)/ [C2 +(T-To)], can be expressed in the same form. They are known to fit well with relaxation data of liquids in equilibrium. Doolittle's free volume equation,lnτ∞1/f, and Adam-Gibbs's entropy equation,lnτ ∞ C/RTS, can be reduced to the Vogel-Fulcher equation with reasonable assumptions on the temperature dependence of the free volume fraction, f, and/or the configurational entropy, S. However, in predicting the relaxation behavior in the nonequilibrium state, the Adam-Gibbs equation can be shown to be a clearly better theory than the Doolittle equation. Moreover, with the Adam-Gibbs equation, it is shown that the kinetic parameters required to describe physical aging are the same as those necessary to describe dielectric relaxation behavior. |
