Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Slot Die Coating of Thixotropic Liquids
Submission Author:
Marcio CARVALHO , RJ , Brazil
Co-Authors:
Carlos Eduardo Sanchez Perez, Danmer Maza, Paulo Roberto de Souza Mendes, Marcio CARVALHO
Presenter: Danmer Maza
doi://10.26678/ABCM.COBEM2023.COB2023-1566
Abstract
Many particle suspensions behave as thixotropic-viscous materials and are present in different industrial processes, including coating applications. Specifically, the production of battery electrodes includes slot coating of thixotropic liquids. In most cases, the flow of slurries and other particle suspensions is described using a generalized Newtonian model that assumes the viscosity to be solely a function of the local deformation rate. However, the viscosity of thixotropic fluids is associated with their microstructuring level. The viscosity does not change instantaneously with the stress (or deformation rate). In the case of imposing constant stress (or shear rate), the microstructure evolves until reaching an equilibrium state, but this process takes time. In the particular case of slot coating, the liquid flows through regions where there are significant changes in the levels of stress. Assuming that the viscosity at each point of the flow is the steady-state viscosity described by a generalized Newtonian model may lead to an inaccurate flow description and predictions of the stable operating conditions. The flow of a thixotropic-viscous liquid through a slot coater is analyzed here using two rheological models: the generalized Newtonian model (GNM) and a thixotropic model that considers the liquid's time-dependent response. The resulting set of fully coupled, non-linear equations is solved by the Galerkin and SUPG Finite Element Method. The results show that the use of a simple generalized Newtonian model to describe thixotropic viscous materials, such as some particle suspensions, can lead to very large errors in the predicted flow behavior. Furthermore, generalized Newtonian models are not able to predict flow phenomena like hysteresis, which could provoke unstable flows. These inaccuracies highlight the need for a more complete model that considers the time-dependency of the flowing liquid within a certain range of flow parameters.
Keywords
Slot coating, Particle suspensions, Thixotropy, Finite Element Method
