The final stages of capillary break-up of polymer solutions

Abstract

The capillary break-up of a polymer solution evolves via a series of stages. After the initial instability a long-lived cylindrical filament is formed, which thins exponentially in time, while the flow is purely extensional. During the final stages of the thinning process, at which the polymers are stretched sufficiently for the filament to become unstable to a Rayleigh-Plateau-like instability, a complex flow pattern develops, which we describe here. Achieving a high spatial resolution well below the optical Rayleigh limit, we describe both the formation of individual droplets as well as that of periodic patterns. Following the periodic instability, a blistering pattern appears, with different generations of smaller droplets. At sufficiently high polymer concentrations, the filament does not break at all, but a solid polymeric fiber with a thickness well below a micron remains. The experiments were performed for various polymer and solvent systems, all of which showed the same qualitative behavior for most of the observed features.

Study of polycaprolactone wet electrospinning process

“…The formation of a 'skin' of coagulated polymer occurs on first contact between a polymer jet filament and the coagulation bath [13]. The 'skin' clearly prevents the fiber from breaking up into spherical drops due to PlateauRayleigh instability [14]. This instability usually appears in the electrospinning of extremely dilute polymer solutions, where the resultant droplet formations are described as a 'pearl effect' on the fibers, 'beads-on-a-string', or simply as 'polymer beads' [15].…”

Wide band Fresnel super-resolution applied to capillary breakup of viscoelastic fluids

“…Its physical properties under elongation are reported in several publications [13,15]. Figure 3 shows the evolution of the fluid capillary bridge.…”

“…[13,14,15] some of the authors of the present studies have shown that in extensional rheometry experiments one can resolve the amplitude of the sinusoidal deformation of the cylindrical liquid filament down to a resolution of 80 nm. This could be achieved by fitting the interface profile that was determined by a simple threshold algorithm with a sinus function, i.e.…”

“…The physical mechanism of the capillary break-up of this solution is described in detail in ref. [13,15] while here we concentrate on the application of this edge-detection technique. Our algorithm evaluates the Fresnel diffraction pattern in the near field as described above.…”

Extensional rheometry of cellulose ether solutions: flow instability

“…Also, several criteria have been suggested for the possibility of such flow instability, including extensibility parameters for polymer chains and dimensionless numbers. This phenomenon has been reported experimentally for a flexible polymer such as PEO (Arnolds et al 2010;Oliveira and McKinley 2005;Oliveira et al 2006;Sattler et al 2008), emulsions (Erni et al 2009), human saliva (Sattler et al 2012), and for the systems with rigid polymers such as xanthan gum solution drop falling under gravity (Smolka and Belmonte 2006) and DNA suspensions (Juarez and Arratia 2011).…”