Analytical Testing Requirements for Food Contact Packaging Barrier Coatings
Aqueous barrier coatings on food contact paperboard require accredited migration, extraction, and permeation testing matching real food simulants and shelf temperatures.
Substrate Edge Wicking
Liquid Migration
Capillary action describes the uncontrolled absorption of fluid into the porous structure of a paper sheet through an exposed boundary. Substrate edge wicking occurs when an aqueous ink, adhesive, or coating agent travels laterally along the internal cellulose network of a cut stack. This phenomenon relies on the tension within the fibre matrix and the size of the interstitial gaps between individual fibres.
Pressure Interaction
High speed printing lines create hydraulic forces that drive moisture into the non-sealed sides of a trimmed roll or sheet. Substrate edge wicking creates visible discoloration or structural weakness at the perimeter of the material. Such distortion limits the usable surface area for high precision graphic applications or specialized converting tasks.
Operators manage this liability by applying edge sealing agents or by adjusting the tension during the drying phase of the manufacturing process.
Material Tolerance
Strict humidity control prevents the internal fibre network from drawing excess moisture into the dry edges of the stock. Substrate edge wicking demonstrates a negative correlation with the degree of internal sizing applied at the wet end of the paper machine. Increased sizing creates a hydrophobic barrier that restricts the movement of fluids away from the application zone.
Proper drying cycles during the production of coated grades further reduce the potential for this lateral fluid transfer by densifying the surface structure. Effective process management ensures that the porous nature of the paper remains contained within the intended print area.