Surfactant Migration Impact on Dynamic Surface Tension in Hardwood Stock
Residual surfactant migration in hardwood stock depresses dynamic surface tension below forty millinewtons per meter, triggering jetting print defects.
Defoamer Carryover
Chemical Residual
Chemical residues from the papermaking process sometimes persist in the finished sheet and interfere with subsequent surface treatments or printing. This defoamer carryover occurs when silicone based or fatty acid surfactants used to control foam in the wet end are not fully washed out or neutralized. Their presence on the substrate creates low energy spots that repel aqueous inks and coatings.
Visual Identification
Visual evidence of this contamination typically appears as small voids or fish eyes in the printed image. When printers encounter defoamer carryover, the ink fails to wet the surface properly and instead pulls back into droplets. Testing for surface tension variation across the web helps identify whether the issue stems from the paper supply or the ink formulation.
Process Impact
Adhesion failures in laminating processes frequently trace back to these persistent surface contaminants. If defoamer carryover exceeds a certain threshold, the bonding strength of films or foils applied to the board decreases greatly. Mills manage this risk by optimizing the dosage of foam control agents and monitoring the filtration systems in the pulp mill to ensure that excess chemicals are removed before the sheet reaches the drying section.
Maintaining high washing standards in the fibre line prevents these residues from reaching the finished product.