Grade Substitution Shipped under an Unchanged Product Name
Unannounced paper grade substitution alters structural fiber bonding and surface chemistry, demanding dockside physical and chemical testing before press loading.
Sheet Delamination
Structural Separation
Failure of the structural bonds within the thickness of a paper or board substrate leads to the splitting of the material into two or more layers. The sheet delamination occurs when the forces applied during printing or converting exceed the internal bond strength of the fibre network. It is most common in multi-ply boards where the interfaces between different layers are the weakest points.
Bond Rupture
Fibres are held together by hydrogen bonding and mechanical entanglement which must resist the pull of high tack inks. During the offset printing process, the tacky ink on the blanket can pull the surface of the paper with enough force to rupture these internal connections. The resulting bubble or tear ruins the print and can contaminate the ink rollers with debris.
Converting Stress
Processing steps such as creasing and folding place intense local pressure on the substrate which can also trigger a separation. If the internal bond strength is too low, the board will split along the fold line rather than bending cleanly. Mills measure this resistance using a Scott Bond tester to ensure the product can handle the mechanical demands of the packaging line.
Maintaining a high level of sheet delamination resistance is essential for high speed production where any failure causes immediate downtime and waste.