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Suppression of Capillary Instability of a Polymeric Thread Via Parallel Plate Confinement.


pdf icon Suppression of Capillary Instability of a Polymeric Thread Via Parallel Plate Confinement. (232 K)
Son, Y.; Martys, N. S.; Hagedorn, J. G.; Migler, K. B.

Journal of Macromolecules, Vol. 35, No. 15, 5825-5833, 2003.

Keywords:

confined geometry; capillary instability; polymamide-6; polystyrene; interfacial tension; Lattice Bohemann

Abstract:

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.