Effect of variations in water content on sub-Tgaging of glass

Abstract
Sodium trisilicate glasses were heat treated for times up to 1000 h at 400 °C. The rate of structural relaxation that occurs under these conditions is controlled by the initial water content as well as by the changes in water content that occur during the heat treatment. The relaxation of the enthalpy is predicted by the Tool–Narayanaswamy model, providing that the initial differences in water content and the changes which occur during the aging process are included in the model via the activation energy for structural relaxation.