Linear rheology of multi-cation polyphosphate glasses

The viscoelasticity of the liquid state of two multi-cation polyphosphate g lasses were studied under oscillatory shear flows in a parallel plate-plate rheometer to determine if organic polymers could be incorporated into the liquids and to provide insights into selection of optimum processing condit ions. The viscosity was time-independent near the glass transition temperat ure and it increased monotonically with time at higher temperatures. The vi scosity increase was exponential at times >84 min and the transition time t o the exponential dependence was dependent on the shear strain. The results were consistent with the Hookean dumbbell model and an average molecular w eight of the liquid structural species was estimated from a modified Rouse theory, making it possible to quantitatively assess melt processability of the multi-cation polyphosphate glasses. (C) 2000 Elsevier Science B.V. All rights reserved.