The effect of non-linearity contribution on the volume and enthalpy relaxation in amorphous materials

The effect of non-linearity contribution to the relaxation behavior of amorphous materials is analyzed with the Tool–Narayanaswamy–Moynihan (TNM) model. It is shown that the rate of relaxation response to a temperature jump can conveniently be characterized on the basis of the stabilization period and the fictive relaxation rate. A simple equation relating these quantities and parameters of the TNM model is derived. This equation separates the contribution of non-exponentiality and non-linearity. It has been tested for PVA and As ₂S ₃ relaxation data. Within the limits of experimental error it seems that volume and enthalpy relaxation in these materials exhibit a similar response that can be well correlated with previously published TNM parameters.