The use of adhesives for flexible packaging depends on the polarity of the polymer molecular state, the environment at which the lamination process will be conducted, and the available system to process the adhesive.
In many cases, bonding can be achieved through a single component; however, to ensure enough cohesion and adhesion, two component adhesive systems are used due to their excellent physical properties. In this regard, a two component PU adhesive was selected to drive a solvent-free lamination of PE and PA film.
The two-component isocyanate(OH) based PU adhesive consisted of hardener and resins, which were mixed at a specified ratio during processing. Ideally, to enhance adhesion in any flexible packaging environment, polymer molecular structures are activated and re-arranged by applications such as plasma, and corona treatment. However, corona treatment was applied to the web films to activate the molecules of the web substrates. The adhesive system was required to possess the thermal stability since processing is conducted beyond ambient temperatures.
