Viscoelastic Creep Compliance and Interfacial Fracture Energy in Paperboard Laminates
Creep compliance dictates long-term carton deformation, while interfacial fracture energy governs delamination under score bending and pallet loads.
Corona Discharge Pretreatment
Surface Modification
Surface treatment methods modify the chemical structure of polymer and paperboard substrates to increase their receptivity to adhesives and inks. In many converting facilities, corona discharge pretreatment applies a high voltage electrical field across the substrate to generate a localized plasma that introduces polar functional groups. This modification raises the surface energy of the material to ensure uniform wetting during subsequent printing operations.
Adhesion Enhancement
Electrical ionization occurs when a high frequency voltage discharges across a narrow gap between an electrode and a grounded roller. This event breaks the molecular bonds on the surface of the paperboard or polymer film, generating free radicals that react with atmospheric oxygen. The resulting carbonyl, carboxyl, and hydroxyl groups increase the chemical affinity for polar adhesives and inks.
Operators regularly monitor the treatment level using dyne test fluids to confirm that the substrate has achieved the required energy level. This step prevents expensive delamination or ink flaking during high-speed folding operations.
Process Limitation
Gradual decay of the treatment effect occurs as the surface molecules reorganize over time. This regression means that the treated substrate must be printed or laminated within a specified time window to maintain its adhesion qualities. Failure to do so requires a secondary treatment on the production line.