Application of the Dynamic Viscoelastic Measuring Method to Oxide Glasses

The viscoelastic properties of phosphate and borate glasses at and below the transition temperature (Tg) were investigated using the dynamic viscoelastic measuring method. The viscosity in these glasses was found to increase with decreasing temperature, from 1012 Pa•s at Tg to between 1015-1016 Pa•s at around 50°C. The free volume-viscosity relation in glass is discussed considering the free volume theory as applied to polymers. As a result, the free volume was found to be applicable to glass at below Tg. But in contrast to polymers, the free volume fraction was found to differ from one glass to another. Glass structure and bond strength are believed to affect the free volume fraction.