Effect of the K/Na ratio in mixed-alkali lime silicate glasses on the rheological and physical properties

Ion exchanged glass surfaces usually have significantly different compositions from the bulk glass. It is, therefore, important to study the composition dependence of stress relaxation in glasses below the glass transition temperature, in order to accurately predict residual stress profiles in glass. In the current study, rheological and physical properties of a commercial soda-lime silicate glass and four custom melted glasses were experimentally determined. To simulate the composition changes in an ion-exchanged layer, the K/Na ratio was varied while keeping the alkali content constant. A weak mixed-alkali effect was found for the viscosity of mixed-alkali lime silicate glass. The thermal expansion coefficients and Young’s moduli of the glasses were also studied.