Modelling of the Plastisol Knife Over Roll Coating Process

Abstract : The knife-over-roll coating process of plastisol formulations for flooring applications has been investigated. The coexistence of smooth spherical PVC particles and rough calcium carbonate aggregates in a Newtonian plasticizer makes this suspension a more complex system than those encountered in the literature. The shear viscosity has been measured with Couette and capillary devices in the wide range of shear rates encountered in the process, resulting in a non-monotonous viscosity curve. A numerical model based on the lubrication approximation theory allows accounting for this non-monotonous behavior. It predicts the deposited thickness, the pressure field between roll and knife and the separating force as a function of the plastisol rheology and the coating parameters.