(181bo) Extensional Rheology of Aqueous Polymer Solutions in Filament Thinning and Microfluidic Contraction Flows | AIChE

(181bo) Extensional Rheology of Aqueous Polymer Solutions in Filament Thinning and Microfluidic Contraction Flows

Authors 

Metaxas, A. E. - Presenter, University of Minnesota
Dutcher, C. S., University of Minnesota
Micklavzina, B., University of Minnesota
Methylcellulose (MC), a methoxy- substituted cellulose ether, is used in a variety of food, pharmaceutical, construction, and consumer applications due to its solubility in water at low temperatures. In addition to its solubility at low temperatures, MC reversibly transitions to a turbid hydrogel upon heating or upon the addition of NaCl to the solution. The gelation phenomenon in aqueous MC solutions is due to the formation of a fibrillar network. While the small amplitude oscillatory and large amplitude oscillatory shear rheological behavior has been characterized for MC solutions, the extensional flow behavior has not been reported. Capillary breakup extensional rheometry (CaBER) can be used to characterize larger molecular weight MC solutions. For MC solutions with lower molecular weights, and therefore lower viscosities, CaBER cannot successfully resolve extensional properties such as the extensional relaxation time and extensional viscosity. Filament stretching using a cross-slot microfluidic channel is a promising method to resolve extensional properties of MC solutions at varying NaCl concentrations. The elastocapillary regime, which determines the extensional relaxation time and viscosity, emerges with the presence of NaCl. This behavior is attributed to the presence of fibrils in the MC solutions containing NaCl annealed at room temperature. The study of the extensional behavior of this already commercially relevant polymer enables new ways to process MC, such as fiber spinning and extrusion.

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