Adhesive Boundary
Interlayer separation force represents the specific peel resistance required to sever the mechanical and chemical bonds holding a converted paperboard structure together. This delamination threshold governs the structural integrity of multi-ply laminates during aggressive converting operations such as die cutting and high-speed folding. Engineers calculate this boundary by measuring the peak load per unit width needed to propagate a forced separation between adjacent plies.
Low interfacial energy creates premature failure during downstream creasing, while excessive adhesion leads to substrate tearing rather than clean ply release. Testing protocols subject conditioned samples to standardized T-peel angles until the adhesive matrix yields completely.
Ply Stress
Multi-layer paperboard constructions experience severe internal shear forces as webs traverse tight roller radii and high-tension drying zones. The delamination threshold dictates how much mechanical fatigue a paperboard structure withstands before internal plies detach under bending loads. Converters measure this internal bonding strength using Scott-type internal bond testers that apply a pendulum impact perpendicular to the sheet surface.
Higher basis weight cartons demand elevated internal bond values to prevent spontaneous layer separation along glued corners and structural crease lines.
Converting Tolerance
Packaging production lines require predictable ply separation behavior to ensure reliable glue penetration and edge sealing during carton erection. Operating windows depend entirely on the delamination threshold staying well above the mechanical stresses imparted by high-speed gluing heads and vacuum pick-up arms. Variations in refining intensity and wet-end chemistry alter the internal bonding plane, shifting the breaking point unexpectedly across a commercial print run.
Quality control laboratories track these interfacial variations continuously to prevent structural failures in finished packaging goods.
