Papers Submitted
Abstract:
We experimentally investigate pendant drops of non-Newtonian
fluid falling in a gravitational field, and report the
effects of semi-dilute concentrations of the polymer
xanthan gum mixed in 80:20 glycerol/water. Our
results demonstrate the macroscopic consequences of charge
screening in extensional flows of polyelectrolyte
polymer solutions. We find the addition of
xanthan gum and potassium chloride (KCl) to the
glycerol/water solution produces dramatic effects: when 780
ppm xanthan
gum is added the drop length just before
pinch-off increases by two orders of magnitude. This length
then is decreased by as much as an order of magnitude as KCl
is
added. We relate this to a known molecular
transition in xanthan gum driven by charge screening of its
self-repulsion.