Experimental Study on Air Entrainment in Slot Die Coating of High-Viscosity, Shear-Thinning Fluids

► Two distinct mechanisms are identified by which air bubble breakup occurs in slot die coating of shear-thinning solutions. ► Mechanism I is assisted by the solution in coating gap, while Mechanism II is facilitated by solution exiting slot die. ► Slot gap has no impact on air entrainment velocity, but smaller slot gaps produce smaller air bubbles. ► Smaller coating gaps delay air entrainment and generate smaller air bubbles. ► Bubble break up shifts from a predominant Mechanism I to Mechanism II as the slot gap or coating gap increases.