3. Coextruded films

This process allows resins to be used to produce, in a single operation, The finished product then only needs to be printed for final identification. It meets the fundamental requirements of any material, i.e., it is machinable, mechanically strong, provides an appropriate barrier to H ₂ O and gases, and allows for leak-proof sealing to ensure proper preservation of the packaged product.

The principle itself is simple, as it involves superimposing different polymers after heating them to their melting point and passing them through a die with only two lips. Throughout the melting phase, the polymers travel through channels without mixing; it is only at the end of the process that they superimpose to create a multilayer film.

Interlayer adhesion, which is the most difficult aspect to control, is...