2 research outputs found
Rheological characterization of commercial highly viscous alginate solutions in shear and extensional flows
The rheological properties of sodium alginate in salt-free solutions were studied by steady shear, dynamic
oscillatory and extensional measurements. This biopolymer
consists of mannuronic and guluronic acid residues that give
a polyelectrolyte character. We applied the scaling theories
and checked their accordance with polyelectrolyte behaviour
for low concentrations with a shift to neutral polymer behaviour
at larger concentrations. This nature was supported by
the effect of the concentration on the specific viscosity, the
relaxation times from steady shear and the longest relaxation
times from small amplitude oscillatory shear (SAOS) measurements.
To analyze the extensional behaviour of the samples,
we conducted a study of dimensionless numbers and
time scales where filament thinning driven by viscous, capillary
or elastic forces is at play. We conclude that an exponential
filament thinning followed by breakup results in the
best regimes that describe the experimental data. Besides, the
data pointed out that alginate in salt-free concentrated solutions
shows strain thinning of the extensional viscosity and
chain rigidity, behaviours that cannot be inferred from the
shear rheometry.This research was supported by funds from the European Research Council (ERC). Project MYCAP (258984) STAR TING GRANTS 2010