Misting of non-Newtonian liquids in forward roll coating

Misting of liquids in forward roll coating is a problem under certain conditions. The relaxation time is known to influence misting but the fundamental mechanisms are not clear. A new mechanism for misting of dilute non-Newtonian liquids was proposed based on visualizations with a high-speed camera. With these liquids, filaments were created which sometimes transformed into beads-on-string structures and the beads were ejected as mist droplets when the structures broke. Misting was quantified by measuring sizes of the generated droplets, their count and mass concentration. The measurements were related to elasticity of the solutions through their relaxation times. Small levels of elasticity reduce the amount of misting, but higher levels lead to an increase.

► A mechanism for misting with dilute polymer solutions in forward roll coating is visualized with a high-speed camera.
► Misting has been related to elasticity of the solutions through their relaxation times.
► Misting was quantified by measuring drop size, count and mass concentration.
► As relaxation times rise: larger and fewer drops are produced; mass concentration of mist falls to a minimum and then rises.
► Slight elasticity suppresses misting whereas more of it aggravates.