Flexographic Aqueous Latex Barrier Coating Viscosity Measurement Fundamentals
Flexographic aqueous latex barrier coating viscosity requires multi-shear rotational measurement to ensure accurate anilox transfer and barrier film continuity.
Kinematic Viscosity
Fluid Dynamics
The ratio of dynamic viscosity to the density of a fluid represents its resistive flow behaviour under the influence of gravity. Paper mill operators track kinematic viscosity when using flow cups or capillary tubes to measure the pumpability and leveling of liquid coatings. It describes how fast a coating fluid will drain, spread, or fill voids on the paperboard substrate.
Measurement Mechanics
Calculated by dividing the dynamic shear viscosity by the mass density of the fluid, this property is expressed in square millimetres per second or centistokes. It is measured by timing the flow of a fixed volume of liquid through a calibrated glass capillary or a standardized orifice. When the fluid density is high, the gravitational force driving it through the opening is greater, which increases the speed of drainage for a given dynamic resistance.
This property is highly dependent on temperature, requiring precise thermal control during any testing procedure.
Process Application
Managing this flow property is essential for running consistent gravure and flexographic printing presses on paperboard. An incorrect ratio causes the applied ink to run too thin or accumulate in the cells of the printing cylinder, which leads to poor image reproduction or dot gain. Monitoring this gravity-driven flow allows converters to adjust solvent addition on the press to maintain the exact coating thickness required for a clean print.