Standard Bench Viscometry Methods for Aqueous Paper Coating Emulsions
Bench viscometry of paper coating emulsions requires standardized temperature control, verified spindle geometry, and multi-shear profiling to ensure runnability.
Cone and Plate Viscometry
Rheological Characterization
The laboratory testing method measures the dynamic viscosity of fluid mixtures under a uniform shear rate across the entire sample gap. In paper coating analysis, cone and plate viscometry allows technicians to characterize the behavior of complex formulations at controlled temperatures. The instrument achieves this by placing a thin film of liquid between a flat surface and a rotating cone with a very shallow angle.
The method is unsuitable for suspensions containing large pigment agglomerates that exceed the dimensions of the narrow gap.
Blade Application
High shear conditions during blade coating require precise simulation before the mixture is loaded into the production machine. Because cone and plate viscometry maintains a constant shear rate throughout the sample, it provides more accurate flow curves than coaxial cylinder systems. Technicians run these tests to identify shear thinning or shear thickening behaviors that could cause application defects on the paper.
The data generated helps engineers optimize the amount of rheology modifiers used in the slurry.
Shear Control
Angle and rotation speed of the cone dictate the precise shear rate applied to the fluid during the run. This precise control ensures that the test conditions mimic the intense forces experienced at the coating blade.