Laminating Process
High-performance adhesive bonding allows the combination of divergent material webs into a single multi-functional structure. In flexible packaging, polyurethane adhesive lamination joins barrier films or metal foils to paperboard substrates to create composite packaging. Applying the reactive adhesive involves coating one web before bringing both webs together in a nip roller.
The adhesive must wet both the porous paper and the non-porous polymer film to ensure an unbroken bond. This technique is used for demanding applications like pet food pouches and liquid cartons. By combining the rigidity of board with the gas-barrier properties of foils, the process produces lightweight containers that extend the shelf life of food products.
Bond Strength
Adhesion durability ensures that the multi-layer sheet does not separate under mechanical stress. During subsequent creasing and folding, polyurethane adhesive lamination provides the shear resistance needed to prevent delamination along the material interfaces. The adhesive must remain flexible after curing to withstand the sharp bends of the box corners.
If the bond fails, the protective barrier is compromised, which can lead to spoilage of the contents.
Chemical Cure
Cross-linking reactions dictate the post-lamination handling times of the rolls. Storing the rolls in a temperature-controlled room ensures that the chemical reaction reaches completion before the material is converted. The reaction can take several days to complete.
Inadequate curing times can lead to adhesive transfer and solvent retention in the finished roll.
