Contact
    Start Publications Dip coating of cylinders with Newtonian fluids
    ←  Publication Finder
    KSV NIMA

    Dip coating of cylinders with Newtonian fluids

    Year: 2022

    Journal: J. Colloid Interface Sci., Volume 607, FEB, page 502–513

    Authors: Zhang, Zhao; Salamatin, Arthur; Peng, Fei; Kornev, Konstantin G.

    Organizations: NIH [P20GM121342]; Ministry of Science and Higher Education of the Russian Federation [075-15-2020-931]; National Science Foundation [IOS-2042937]; SC EPSCoR/IDeA Program under NSF [OIA-1655740]

    Keywords: Dip coating; Lubrication flow; Landau-Levich-Derjaguin (LLD) theory; Capillarity

    Hypothesis: The Landau-Levich-Derjaguin (LLD) theory is widely applied to predict the film thickness in the dip-coating process. However, the theory was designed only for flat plates and thin fibers. Fifty years ago, White and Tallmadge attempted to generalize the LLD theory to thick rods using a numerical solution for a static meniscus and the LLD theory to forcedly match their numeric solution with the LLD asymptotics. The White-Talmadge solution has been criticized for not being rigorous yet widely used in engineering applications mostly owing to the lack of alternative solutions. A new set of experiments significantly expanding the range of White-Tallmadge conditions showed that their theory cannot explain the experimental results. We then hypothesized that the results of LLD theory can be improved by restoring the non-linear meniscus curvature in the equation. With this modification, the obtained equation should be able to describe static menisci on any cylindrical rods and the film profiles observed at non-zero rod velocity. Experiment: To test the hypothesis, we distinguished capillary forces from viscous forces by running experiments with different rods and at different withdrawal velocities and video tracking the menisci profiles and measuring the weight of deposited films. The values of film thickness were then fitted with a mathematical model based on the modified LLD equation. We also fitted the meniscus profiles. Findings: The results show that the derived equation allows one to reproduce the results of the LLD theory and go far beyond those to include rods of different radii. A new set of experimental data together with the White-Tallmadge experimental data are explained with the modified LLD theory. A set of simple formulas approximating numeric results have been derived. These formulas can be used in engineering applications for the prediction of the coating thickness. (c) 2021 Elsevier Inc. All rights reserved.
    View publication