Suppression of Capillary Instability of a Polymeric Thread Via Parallel Plate Confinement.
Suppression of Capillary Instability of a Polymeric
Thread Via Parallel Plate Confinement.
Son, Y.; Martys, N. S.; Hagedorn, J. G.; Migler, K. B.
Journal of Macromolecules, Vol. 35, No. 15, 5825-5833,
confined geometry; capillary instability; polymamide-6;
polystyrene; interfacial tension; Lattice Bohemann
We investigate the stability of a polymer thread
imbedded in a matrix that is confined between two
parallel plates. Utilizing a combination of experiments,
numerical simulations (Lattice-Boltzmann) and surface
area calculations we find substantial deviations from
the classical results when the diameter of the thread
(Do) is comparable to the height (H) of the matrix. We
find three regimes as a function of H/Do; for H/Do > 3,
the thread breaks up into droplets through a finite
wavelenght axisymmetric capillary instability as
described by Rayleigh and Tomotika. For 1.3 > H/Do < 3,
the effects of the confinement are felt; the shape
becomes non-axisymmetric, the early- stage growth rate
decreases, and the wavelength increases. For
sufficiently low H/Do, we observe that the thread is
stable with respect to the capillary instability for
long times. the simulations qualitatively agree with the
experiments and reveal that the necks of the
fluctuations are circular. A simple surface area
consideration then shows that as the wall-induced
asymmetry of the fluctuation increases, the minimally
unstable wavelength increases, and eventually diverges.