Delamination Threshold
Bond mechanics dictate how multi-ply cartonboard resists splitting under stress, and interfacial fracture energy quantifies the exact work required to propagate a crack between structural layers. Measuring this parameter involves peeling bonded plies at a controlled angle while recording the tensile force per unit width. Cylinder mould machines determine the initial ply bond during wet web formation through hydrodynamic shear and pressing pressure.
Starch chemistry and refining degrees inside the stock preparation plant dictate the baseline bonding force before the sheet reaches the drying section. Deficient refining yields low internal bond strength, causing corrugated board liners and folding boxboards to delase during high-speed printing operations.
Cure Kinetics
Resin crosslinking speed within laminated flexible packaging webs governs the final resistance against mechanical peel forces. Laminating adhesives undergo chemical reactions that transform liquid polymers into solid networks, establishing the permanent bond between aluminium foil and polymer films. Thermal tunnels and radiation curing units supply the activation energy needed to complete polymerization before the reel enters the slitting machine.
Solvent retention within the adhesive layer softens the polymer matrix, degrading the bond strength below the minimum tolerance required for retort pouches. Precise web tension control prevents residual stresses from accumulating inside the multilayer structure during the winding process.
Conversion Stress
Die-cutting plates and folding creasing bars exert high localized shear forces that test the internal cohesion of heavy substrates. Converter machinery demands a specific energy threshold to prevent ply separation when blanks undergo rapid bending around 180-degree angles in high-speed folding and gluing lines. Cartonboard must absorb this mechanical deformation without internal delamination or blister formation along the scored edges.
Laminating strength tolerances are specified in joules per square metre to ensure finished packaging withstands the hydraulic pressures generated during liquid carton filling. Mechanical failure occurs whenever the applied conversion stress exceeds the measured boundary limit of the material.
