Quantifying Matting Agent Displacement in Package Printing Overprint Coatings
Quantifying matting agent displacement requires z-axis Raman depth profiling and strict viscosity recovery control to stop gloss drift and scuff failure.
Marangoni Convection
Gradient Fluidity
Surface tension differences drive the lateral flow of liquids within thin films during drying processes. Marangoni convection occurs when thermal or solute gradients create variations in surface tension across a liquid interface. Fluids migrate from areas of low surface tension to regions of high surface tension until equilibrium or total evaporation halts the movement.
Drying Mechanics
Coating formulations rely on uniform spread rates to ensure consistent thickness across a web. When a wet film dries, solvents evaporate unevenly and create temperature shifts that trigger marangoni convection in localized pockets. These movements generate surface defects such as orange peel or craters if the flow intensity exceeds the stabilization threshold of the binder system.
Adjusting solvent volatility or adding surfactants dampens these internal currents to maintain a smooth deposit.
Performance Consequences
Defects induced by these interfacial currents permanently alter the barrier properties and printability of treated substrates. Paper mills and coating facilities monitor the drying zone environment to prevent uncontrolled shifts in surfactant concentration that feed such currents. High speed coating lines require precise control over heat transfer rates because rapid drying accelerates the onset of instabilities.
Excessive internal flow patterns reduce the final gloss level of the dried film and disrupt the homogenous distribution of functional pigments.