Rheology and Phase Behavior of the System PBZT-Phosphoric Acid-Water.
BRISTOL UNIV (UNITED KINGDOM) H H WILLS PHYSICS LAB
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Our assignment was to map out the viscosity of PBZT in a suitable solvent as a function of temperature, concentration, and shear rate. The richness and associated complexity of the system, however, forced us to place the matter in a much broader framework. Which, thanks to our wide ranging and possibly unique experience into this system, we were in a position to do. As PBZT is difficult to dissolve the choice of solvent is very limited. The most common is polyphosphoric acid used also in synthesis, characterization and processing. This solvent, as our studies have shown, is itself a complex system of polyphosphoric acids of different degrees of polycondensation and water in equilibrium, itself affected by temperature. In fact, in the polycondensation degrees used in the processing of PBZT, it is a mixture of orthophosphoric acid OPA and diphosphoric acid DPA. This, with PBZT as a solute, gives rise to a complex phase diagram involving a variety of phases as previously investigated here. Any meaningful interpretation of measured viscosity values will need to refer to this phase diagram, the variation of viscosities with temperature and concentration and to a lesser extent with strain rate is strongly related to the phase behavior.
- Organic Chemistry
- Polymer Chemistry
- Fluid Mechanics