Plastic packaging - Polymers used

The various polymers used in the packaging industry must fulfill three main functions:

• presentation;

• preservation;

• machinability.

This is why, in many cases, multiple materials are combined either with one another— – —through processes such as lamination, extrusion-lamination, extrusion-coating, tandem extrusion, and, increasingly, coextrusion (see “Plastic Packaging: Processing Methods and Applications” [AM 3 576] )—or by adding paper and/or aluminum foil.

The presentation is designed to attract potential buyers through its graphics and colors, and quickly highlights the category in which the customer typically makes purchases (holiday products, promotional launches, or bulk purchases).

Shelf life ranges from a few days to 24 months, with or without a cold chain, which involves different levels of barrier properties (O ₂ , H ₂ O, UV) (see “Barrier Properties of Polymers Used in Packaging” [AM 3 160] ) as well as seals that are either relatively or absolutely airtight.

Machinability refers to a material’s suitability for use with one of the available technologies: pre-made pouches, vertical form-fill-seal machines, horizontal form-fill-seal machines, thermoforming machines, tray and jar sealing machines, and folding machines (see “Packaging Machinery. Dry Goods and Small Items” [AG 6 601] ).

The R&D team must address all of these constraints in order to meet the specifications provided by the marketing department. Their knowledge of polymer properties and processing options guides their decisions.