Rheology of plastisol formulations for coating applications

A plastisol is a suspension of PVC particles and mineral fillers in a liquid phase composed of plasticizer and adjuvants. Plastisol formulations are commonly used in coating processes for flooring application. In the knife-over-roll process, they are subjected to a wide range of shear rates (0-10(5) s(-1)). They are adjusted in order to fulfil the target end-use properties but their processability depends on their rheology. Plastisol based on three PVC resins with or without mineral filler have been investigated using a Couette device and a capillary rheometer. Results show a high impact of PVC particle content, particle sizes and distribution on rheology: a polydisperse formulation displays a shear-thinning behavior in the whole shear rates range and exhibits yield stress; a monodisperse formulation shows a shear thinning behavior at low shear rate, followed by a Newtonian plateau, then a more or less pronounced dilatancy peak depending on plasticizer rate and finally another shear-thinning behavior; a bidisperse resin stands in between. Filler content also impacts the rheology: shear thickening effects at intermediate shear rates decrease or even disappear; however, the viscosity increase is important for low shear rates and depends on the filler particle size and particle size distribution. POLYM. ENG. SCI., 57:982-988, 2017. (c) 2016 Society of Plastics Engineers