Cellulosic Microfibril Moisture Binding Mechanisms in Packaging
Microfibril moisture binding follows GAB sorption kinetics where mesopore condensation above M0 plasticizes fiber networks, requiring crosslinking to preserve barriers.
Z Directional Delamination
Separation Mode
Structural failure mode occurs when the internal layers of a paperboard sheet separate along a plane parallel to the surface. Z directional delamination is typically caused by insufficient bonding between the fibre plies or by excessive shear stress during the printing process. It results in a complete loss of stiffness and can cause the outer surface of the board to peel away.
High-Speed Printing
Printing presses use inks with high tack that pull on the surface of the paper as it leaves the blanket. If the internal strength of the board is lower than the tack of the ink, the plies will pull apart. This often happens at the interface between different types of pulp, such as a white top liner and a recycled middle layer.
Starch application at the wet end of the paper machine is the primary method for preventing this separation.
Production Stability
Packaging that has delaminated is unusable for retail display and cannot protect its contents effectively. It also causes downtime in the print shop as the separated layers can wrap around the rollers and damage the equipment. Quality control checks using the Scott Bond test are used to monitor this property during production.
Ensuring a robust internal bond is a requirement for any premium packaging board. The use of long-fibre kraft pulp in the core layers can increase the resistance to this failure mode.