When it comes to bonding paper, PE and aluminium, the latter is the most difficult to adhere. In fact, whilst the surfaces of aluminium sheeting may appear smooth, an examination with an electron microscope may reveal various imperfections. These are caused by the used laminating systems that leave traces of oil on the surfaces that, even in small quantities, penetrate the imperfections and thus inhibit adhesion.
In addition, the aluminium strips can be contaminated by contact with paper and ink printing. A system must thus be used to perfectly clean the surfaces and create the bonds necessary for adhesion, with the most effective being flame treatment that guarantees the superficial cleaning and necessary adhesion through to obtaining wettability with distilled water.