Abstract
Fibers can be coated by passing them through a solution. In this paper, the thickness of the entrained film on the fiber was experimentally measured for various solutions such as water, polyacrylamide (PAA), and polyethylene glycol (PEG) aqueous solutions, and the effect of rheological properties of the solutions on the film thickness was studied. For low viscosity materials, such as water, the film thickness followed the Landau-Levich-Derjaguin (LLD) equation at low capillary number but, due to the inertial effect, it deviated away from the equation as the withdrawal velocity of fiber increased. The 3-D direct numerical simulation was performed to confirm the inertial effect on the entrained film thickness. For polymeric solution, the film-thickening rate against the capillary number was estimated by the LLD equation at low capillary number. However, the absolute value of the film thickness was far larger than that from the equation even when the withdrawal velocity was low. It could be considered the elongational deformation of polymer around fiber, which can be observed in the tubeless siphon phenomenon, affected the thickness of the polymeric film.
