Newtonian coating liquids in slot coating bead flows
In a recently published study, scientists investigated the influence of the upstream meniscus shape on the dynamic wetting and operating limits of Newtonian coating liquids in slot coating bead flows.
The coating bead flow and operability window for Newtonian coating liquids are theoretically and experimentally investigated in the slot coating process, with a focus on the shape of the upstream meniscus and contact angles. From the flow visualisation in the coating bead region, the contact angles of the upstream meniscus were measured by changing the flow rate and web speed under uniform operating conditions.
Accurate prediction with Navier-Stokes models
It was confirmed that the dynamic contact angle is closely related to the capillary number in this process, based on the Hoffman–Voinov–Tanner model. The viscocapillary and two-dimensional Navier–Stokes models using the experimentally observed contact angles accurately predicted the coating bead dynamics and operability windows for two Newtonian liquids.
The study is published in: Journal of Coatings Technology and Research September 2018, Volume 15, Issue 5, pp 1067–1076.
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