High and Medium Range Viscometers and Their Test with Some Alkali Silicate Glasses

Viscometers capable of measuring a wide range of viscosity covering 1-1012Pa·s were developped and tested for some alkali silicate glasses. For the range of 103-108Pa·s, a conventional viscometer was used with a 5mm wide and 10mm long penetration tip of alumina tube, which lowered the measurable viscosity range maintaining the precision. For the range of 108-1012Pa·s, the beam-bending principle was utilized. By applying load to a sheet glass specimen with an alumina tube, and by heating at 3°C/min, viscosities in the range of 108-1012Pa·s were measured in a single run. It was shown that these viscometers can be applied to Li2O-Na2O-2SiO2 glasses. It was demonstrated that glass transition temperature Tg agrees well with the temperature at which a viscosity of 1012Pa·s was attained. It was also found that the viscosity vs. temperature relationship can be described by the Fulcher's type equation over the wide range temperature with good accuracy.