Effect of Extensional Properties of Polymer Solutions on the Droplet Formation via Ultrasonic Atomization

Ultrasonic atomization was conducted using 2.4 MHz ultrasound generator to produce polymeric particles from the solutions of water-soluble polymers like poly (ethylene oxide) (PEO), poly(vinyl alcohol) (PVA), and poly(vinyl pyrrolidone) (PVP). In the series of solutions containing these polymers of various molecular weights, the shear viscosity and surface tension were varied; such differences, however, could not account for the observed trends in the atomization behavior. It was found that the availability of droplet formation and size of the droplets depend strongly on the extensional characteristics of polymer solutions along with the apparent extensional viscosities and the longest relaxation times. The extensional properties of polymer solutions were effectively measured by capillary breakup extensional rheometry (CaBER) and provided a rational basis to understand the essential role of fluid viscoelasticity in ultrasonic atomization. POLYM. ENG. SCI., 51:2446-2452, 2011. (C) 2011 Society of Plastics Engineers