Filament Dissolution
Spontaneous surface tension driven necking drives a liquid cylinder to destabilize and split into discrete droplets. In paper converting and adhesive application, capillary breakup governs the physical mechanism by which fluid bridges between transferring surfaces fracture into separate drops. The process originates from axial diameter perturbations that grow once the perturbation wavelength exceeds the liquid column circumference.
Surface Tension
Interfacial forces act to minimize total surface area, drawing fluid away from narrow regions of the liquid bridge toward thicker sections. Viscous resistance within the liquid column slows fluid displacement, while liquid elasticity counteracts the driving capillary pressure. In high-speed coating processes, capillary breakup dictates whether liquid filaments snap cleanly at the nip exit or stretch into elongated structures that collapse unevenly.
The balance between capillary pressure and fluid inertia dictates the characteristic timescale of bridge collapse. Formulations with high surface tension accelerate filament thinning, forcing rapid filament cleavage before mechanical equipment moves beyond the transfer zone.
Pinch Threshold
Physical limits occur when extensional viscosity dominates surface tension forces. Suppression of capillary breakup causes liquid filaments to remain intact across wide gap distances, leading to web contamination on high-speed folder-gluers. Clean filament pinch disappears when high molecular weight polymers enter the formulation.
