Plastic packaging - Polymers used

The various polymers used in packaging must fulfil three main functions:

• presentation ;

• conservation ;

• machinability.

This is why, in many cases, several are combined either – by complexing, extrusion-lamination, extrusion-coating, tandem extrusion and increasingly by coextrusion (see "Plastic packaging. Converting processes and applications" [AM 3 576] ), or by adding paper and/or aluminum foil.

The presentation is designed to appeal to the potential buyer, through graphics and colors, and quickly synthesizes the segment in which the customer traditionally shops (festive product, promotional launch or batch).

Shelf-life ranges from a few days to 24 months, with or without a cold chain, which implies different levels of barrier (O ₂ , H ₂ O, UV) (see "Barrier properties of polymers used in packaging" [AM 3 160] ) but also seals of relative or, on the contrary, absolute tightness.

Machinability is the material's suitability for use on one of the available technologies: prefabricated bags, vertical machine, horizontal machine, thermoforming machine, tray and pot sealing machine, folding machine (see "Packaging machinery. Dry products and small items" [AG 6 601] ).

The R&D team must respond to all these constraints in order to satisfy the specifications provided by the marketing department. Knowledge of the properties of polymers and the possibilities of their processing guides the team in its choice.