Predicting physical and chemical properties of bioactive glasses from chemical composition. Part 1: Viscosity characteristics

Viscosities of a series of glasses of interest for their bioactivity were determined in the range from 10(10) dPas up to about 10 dPas. At low temperatures the viscosities were measured by hot stage microscopy and at high temperatures With a rotational viscometer. Experimental glass compositions within the system Na(2)O-K(2)O-MgO-CaO-B(2)O(3)-P(2)O(5)-SiO(2) were chosen statistically to enable statistical analysis of the viscosity data and the development of equations describing the viscosity as a function of glass composition and melting temperature. Temperatures at specified viscosity levels close to glass transition or glass melting could be calculated With good accuracy from the oxide composition. In the medium viscosity range, crystallisation of glasses disturbed the viscosity prediction and only approximate models for the whole viscosity range were obtained.