Levelling of coating suspensions

Surface tension driven levelling of coating suspensions is studied using a mathematical model based on traditional computational fluid dynamics and dy namic simulation of particle motion. Microscopic mechanisms and parameters that control the levelling of suspensions are investigated. High particle c oncentrations 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 structure s and promote levelling, whereas attractive forces create flocs that reduce the levelling. The reduction of levelling caused by various microstructure s can lead to a nonuniform coating distribution along the coated substrate.