Levelling of coating suspensions

Surface tension driven levelling of coating suspensions is studied using a mathematical model based on traditional computational fluid dynamics and dynamic simulation of particle motion. Microscopic mechanisms and parameters that control the levelling of suspensions are investigated. High particle concentrations and flocculated state of the suspension reduce the levelling flow in thin films. Nonhydrodynamic forces determine the microstructure of the coating layer: repulsive interparticle forces lead to layered structures and promote levelling, whereas attractive forces create flocs that reduce the levelling. The reduction of levelling caused by various microstructures can lead to a nonuniform coating distribution along the coated substrate.