Abstract
A final coating of uniform thickness implies good leveling and the avoidance of defects during film formation. Though generally desired, this objective is often unmet. The outcome of a coating process depends on the nonlinear interaction of the rheology, process variables, and substrate geometry. Understanding the role of rheology is complicated by difficulties in linking fundamental rheological properties with coating performance. During a coating process, forces of varying type, magnitude and duration act on the fluid film. For non-Newtonian coatings the viscosity varies with both time and position within the coating layer, making predictions of flow behavior quite difficult. One answer is computer simulation, using numerical techniques to solve a set of nonlinear differential equations governing the flow. The rheological and other physical properties are parameter values for the program.
We present results of mathematical modeling and numerical simulation of a coating imperfection known as a “dripmark.” The model includes non-Newtonian rheology, substrate shape, surface tension, and gravity. We compare theoretical prediction with experimental observation in a study of two architectural paints. We also describe a new method of quantitatively measuring the surface profile of a coating defect.
Similar content being viewed by others
References
Strivens, T.A., “The Rheology of Paints,” inPaint and Surface Coatings: Theory and Practice, Lambourne, R. and Strivens, T.A. (Eds.), 2nd ed., Woodhead Pub. Ltd., 1999.
Schoff, C.K., “Surface Defects: Diagnosis and Cure,”Journal of Coatings Technology,71, No. 888, 56 (1999).
Pierce, P.E. and Schoff, C.K., “Coating Film Defects,” 2nd Edition,Federation Series on Coatings Technology, Blue Bell, PA, 1994.
Kornum, L.O. and Raaschou-Nielsen, H.K., “Surface Defects in Drying Paint Films,”Prog. Org. Coat., 8, 275 (1980).
Bierwagen, G.P., “Surface Defects and Surface Flows in Coatings,”Prog. Org. Coat., 19 (1), 59 (1991).
Weidner, D.E., Schwartz, L.W., and Eley, R.R., “Role of Surface Tension Gradients in Correcting Coating Defects in Corners,”J. Coll. & Interf. Sci., 179, 66–75 (1996).
Overdiep, W.S., “The Leveling of Paints,”Prog. Org. Coat., 14, 159 (1986).
Wilson, S.K., “The Derivation and Analysis of a Model of the Drying Process of a Paint Film,”Surf. Coat. Int., 4, 162 (1997).
Schwartz, L.W., Roy, R.V., Eley, R.R., and Petrash, S., “Dewetting Patterns in a Drying Liquid Film,”J. Coll. Interf. Sci., 234, 363–374 (2001).
Hoeflaak, M., “Edge Coverage and Rheological Behaviour of Coating Materials During Film Formation,”Surf. Coatings Australia, 6, July 1987.
Bierwagen, G.P., “Surface Energetics,” Chap. 5.4 inASTM Paint and Coatings Testing Manual, 14th ed., Koleske, J. (Ed.), American Society for Testing and Materials (ASTM), West Conshohocken, PA, pp. 369–382, 1995.
Klarskov, M., Jakobsen, J., and Saarnak, A., “Verification of the Orchard Leveling Analysis,”Rheology, 92, 30, March (1992).
Kim, J.S., Kim, S., and Ma, F.,J. Appl. Phys., 73, 422–428 (1993).
Bird, R.B., Armstrong, R.C., and Hassager, O.,Dynamics of Polymeric Liquids, Wiley, New York, 1977.
Schwartz, L.W., Moussalli, P., Campbell, P., and Eley, R.R.,Trans. Inst. Chem. Engrs., 76, 22–29 (1998).
Weidner, D.E. and Schwartz, L.W., “Contact Line Motion of Shear-Thinning Fluids,”Phys. Fluids, 6 (11), 3535–3538 (1994).
Schwartz, L.W. “Unsteady Simulation of Viscous Thin-Layer Flows,” inFree-Surface Flows with Viscosity, Tyvand, P. (Ed.), pp. 203–233, Computational Mech. Publ., Southampton, 1997.
Orchard, S.E.,Applied Scientific Research, Section A, Vol. 11, 451, 1962.
Peaceman, D.Fundamentals of Numerical Reservoir Simulation, Elsevier, Amsterdam, 1977.
Schwartz, L.W. and Eley, R.R., “Flow of Architectural Coatings on Complex Surfaces; Theory and Experiment,”J. Eng. Math. (2002), in press.
Eley, R.R., “Rheology and Viscometry,” Chap. 33,ASTM Paint and Coatings Testing Manual, 14th ed., ASTM, Philadelphia, 333–368, 1995.
Eley, R.R., “Principles and Methods of Rheology in Coatings,” inEncyclopedia of Analytical Chemistry: Instrumentation and Applications, Meyers, R.A. (Ed.), J. Wiley & Sons, Ltd., 2001.
Author information
Authors and Affiliations
Additional information
Strongsville Research Center, 16651 Sprague Rd., Strongsville, OH 44136.
Dept. of Mechanical Engineering, University of Delaware, Newark, DE 19716.
Rights and permissions
About this article
Cite this article
Eley, R.R., Schwartz, L.W. Interaction of rheology, geometry, and process in coating flow. Journal of Coatings Technology 74, 43–53 (2002). https://doi.org/10.1007/BF02697974
Issue Date:
DOI: https://doi.org/10.1007/BF02697974