Characterizing the kinetics of volume recovery in glasses by instantaneous temperature‐jump experiments

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Abstract
This article proposes a temperature‐jump (T‐jump) approach for characterizing the kinetics of volume recovery in glassy materials. The kinetic characterization is based on the Kovacs‐Aklonis model. This incorporates a retardation‐time spectrum which shifts according to both the temperature and the instantaneous volume. The proposed experiments involve measuring the change in recovery rate caused by an abrupt temperature jump. Although an analogous procedure has been used to determine the activation energy for linear viscoelastic creep, the analysis for volume recovery is complicated by its inherent nonlinearity. Nevertheless, accounting for the nonlinearity by a reduction of the time scale permits the T‐jump results to be analyzed. In particular, the T‐jump approach can be used to: (i) test a particular functional form for the shift factor and (ii) determine the previously unmeasurable parameter x, which defines the relative importance of the temperature dependence and the volume dependence in this function. In addition, numerical simulations indicate that the proposed method can be implemented in the laboratory.