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.
Flexographic Rheology
Ink Hydraulics
Liquid resistance inside the printing deck governs how efficiently color transfers from the engraved cylinder to the porous substrate. Flexographic rheology defines the relationship between applied force and fluid deformation within these high speed systems. Measuring the viscosity and yield stress of the ink ensures the pump maintains constant circulation without cavitation.
High shear rates during the transfer process cause the ink to thin temporarily, allowing precise deposition within the micro cells of the plate.
Flow Stability
Stationary storage tanks require lower stress values to prevent pigment settling and ensure uniform suspension of solids before the pump initiates movement. Flexographic rheology maintains the necessary viscosity profiles to facilitate rapid transition from a static state to a turbulent flowing state. Chemical additives within the ink formulation influence this transition point, preventing structural breakdown during long runs on the press.
Printers adjust the thermal controls of the ink deck to compensate for environmental temperature variations, keeping the flow characteristics within strict operational limits.
Print Tolerance
Consistent coating performance relies upon the ability of the fluid to recover structure immediately after passing through the nip point where pressure drops suddenly. Flexographic rheology dictates the dot gain and edge sharpness achieved on the final product, as fluids with incorrect viscoelastic properties fail to remain within the intended boundaries of the design. Insufficient structural recovery leads to unwanted ink migration across the surface of the board, reducing the clarity of fine line work and text.
Controlled elastic recovery in the ink film prevents common defects like splattering or poor ink laydown on fast running converting equipment.