Structural Integrity
Internal adhesion failure describes the physical separation of individual plies or functional segments within a paperboard or multi-laminated substrate. Layer delamination represents the total breakdown of the chemical or mechanical bonds holding these components together under external stress. This separation reduces the rigidity of the stock and ruins the protective barrier properties of the final package.
Converting equipment often triggers this condition when excessive tension exceeds the internal bond strength of the paper structure.
Bonding Mechanics
Aqueous adhesive distribution determines the threshold at which the composite remains stable during high speed folding or creasing operations. Microscopic pockets of air or uneven moisture content within the sheet disrupt the interface between plies. Low sizing levels or poor fibre orientation in the base board exacerbate these weaknesses.
Production settings rely on pull tests to quantify the force required to force the sheets apart. Moisture migration through a coating layer often softens these internal bonds before the converting phase begins.
Failure Consequences
Print quality degrades rapidly when the surface plies lift away from the supporting body during impression or drying. Excessive separation creates debris that accumulates on rollers and blankets, forcing frequent machine stops. Vacuum fed systems fail to maintain pick up when the top ply detaches from the supporting sheet.
Increased scrap rates arise whenever the mechanical load of the process exceeds the internal tenacity of the material. A material with insufficient cross direction strength faces high risk of rupture under standard bending forces.
