3. Coextruded films

This process uses resins to produce a finished product in a single operation. The finished product, which only needs to be printed for final identification. It meets the fundamental requirements of any material, i.e. to provide machinability, mechanical resistance, an appropriate barrier to H ₂ O and gases, and finally to enable tight seals to be obtained in order to obtain good preservation of the packaged product.

In itself, the principle is simple: different polymers are superimposed on one another, having reached their melting point, and passed through a die with only two lips. During the entire melting phase, the polymers pass through channels without mixing, and it's only at the end of the process that they superimpose to create a multilayer film.

Interlayer adhesion, the most difficult...