Structural Fracture
Polymer coating separation during high speed folding operations occurs when an applied barrier film or extruded polyethylene layer loses adhesion to the underlying paperboard substrate. Surface skin delamination compromises moisture and grease resistance by creating micro channels through which liquids migrate into the cellulose fibers. Converters measure this defect under standardized peel tests where force is recorded in Newtons per meter of width.
Lamination failure stops appearing once bond strength exceeds the internal cohesion limit of the base paperboard stock.
Adhesion Mechanics
Corona discharge treatments applied prior to extrusion coating increase surface energy levels measured in dynes per centimeter to promote mechanical and chemical bonding between dissimilar materials. Extrusion temperatures exceeding specific thresholds degrade polymer chains and weaken the interface before nip rollers apply pressure. Primer applications mitigate bond failure by anchoring the aqueous dispersion coating directly onto smooth clay coated paperboard surfaces.
Barrier Failure
Liquid packaging cartons experience structural compromise along crease lines when internal ply separation allows fluid penetration under hydrostatic pressure. Seal integrity testing reveals pinhole leakage paths originating from localized areas where the polyethylene skin detaches from the board during creasing die compression. Substrate moisture content exceeding specific tolerances vaporizes rapidly inside heat sealing stations and generates internal steam pressure that forces the barrier film away from the paperboard.
