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.
Vane Geometry
Spindle Design
Spindle design configurations featuring multiple blades radiating from a central shaft are used to test highly structured or particulate-heavy fluids. Incorporating vane geometry consists of four or more thin blades arranged symmetrically around a central pin to measure the viscosity and yield stress of complex suspensions. This design is used to evaluate paper coatings, starch pastes and high-solids mineral slurries that are prone to wall slip when tested with smooth-surfaced spindles.
Slip Prevention
When a smooth spindle is rotated in a highly structured fluid, a thin layer of low-viscosity liquid often forms next to the spindle surface, causing the spindle to slip rather than shear the bulk material. The blades of this specialized design trap a portion of the sample between them, forcing the material to shear along a cylindrical boundary defined by the vane dimensions. This action provides an accurate measurement of the sample’s true yield stress and flow behavior.
The result is a more reliable analysis of structured fluids that are stored in mill supply tanks.
Slurry Testing
Highly concentrated clay and calcium carbonate slurries are tested with this tool to monitor their behavior during long storage periods. This testing prevents problems with material settling and pump blockages in the mill’s distribution system.