In Situ Rheological Measurement of an Aqueous Polyester Dispersion during Emulsification
2015
Goger, A. | Thompson, M. R. | Pawlak, J. L. | Lawton, D. J. W.
Rheological analysis of a complex fluid system like an aqueous polymer dispersion can be challenging but can reveal mechanistic information as the viscous melt is emulsified. A pressurized vessel was used as a rheometer, based on the Metzner–Otto approach, to evaluate formulation variables where the developed morphology of a polyester/water mixture was shear-dependent. The parameters of the study were resin-to-water ratio (R/W), surfactant (type and concentration), and process variables of impeller speed and temperature. Transient in situ information on the system during the mixing of water into the molten polymer showed that a rapid, near-instantaneous decrease in the torque on the impeller occurred consistently around 2% water addition, related to the onset of the developed morphological state. It was observed to only demonstrate a drop in the torque for high shear rates and only with the appropriate content of surface-active species, revealing the chemical and physical parameters necessary to emulsify the polyester melt.
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