Flexographic Barrier Coating Viscosity Measurements for Aqueous Latex Formulations
Aqueous latex barrier performance depends on controlling dynamic high-shear viscosity to ensure complete anilox cell release and eliminate film pinholing.
Foam Control Additives
Surface Tension Management
Chemical agents composed of siloxanes or hydrophobic particles prevent air entrainment in paper coatings and aqueous inks by lowering liquid tension. Foam control additives function through rapid migration to the air liquid interface where they rupture existing bubbles and inhibit the formation of new gas pockets. Proper dosage prevents pinholes and streaks on the substrate surface during high speed application.
Coating Stability
These compounds destabilize the lamella of a bubble by providing a non polar pathway for air escape. Dispersed particles adsorb to the bubble surface, changing the surface energy until the bubble wall collapses under atmospheric pressure. Operators balance the concentration of these substances against the binder chemistry to ensure that viscosity and gloss levels remain stable across the entire production run.
Excess usage leads to cratering or fish eyes when the chemical prevents the coating from wetting the paper stock uniformly.
Application Parameters
Converting lines require specific anti foam performance depending on the shear rate of the coating head. Low viscosity systems demand fast acting components to address instantaneous bubble formation at the applicator roll, while high solids coatings necessitate long term persistence to survive the circulation system. The choice of additive depends on the compatibility with latex resins and natural binders found in the specific coating formulation.
Efficiency in this area dictates the physical integrity of the print surface and the final optical density of the finished product.