Splashing of Complex Fluids: Role of Particles and Polymers

The way complex fluids - whether water-soluble synthetic polymers, solid particles, or hydrocolloids - influence drop splashing, has had conflicting results in the literature. To understand the difference among the additive types on the influence and onset of drop splashing, the complex fluid drop impacts on Glaco-coated glass slides were experimentally studied utilizing side and bottom view high-speed imaging techniques. Various additive types, including kaolinite, laponite, sodium alginate, polyethylene glycol, and polystyrene (particles) were used to probe the splashing and spreading behaviors on horizontally-oriented substrates. The addition of polyethylene glycol (PEG) was shown to splash below the splash threshold of water above a critical concentration of PEG (i.e., c*), which cannot be explained with the conventional splash theories. PEG, glycerol-water and sodium alginate (SA) all splashed below the splash threshold of water whereas all other solutions splashed at the water threshold. These results show the need for alternative theories for describing the splash of complex fluid drop impacts, which have a variety of commercial applications.