Linear rheology of multi-cation polyphosphate glasses

The viscoelasticity of the liquid state of two multi-cation polyphosphate glasses 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 conditions. The viscosity was time-independent near the glass transition temperature and it increased monotonically with time at higher temperatures. The viscosity increase was exponential at times >84 min and the transition time to the exponential dependence was dependent on the shear strain. The results were consistent with the Hookean dumbbell model and an average molecular weight 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.