Rigid and flexible multiply packaging materials - Lamination and coextrusion

Packaging materials must combine a number of qualities, both in terms of enhancing and protecting packaged products, and in terms of their actual use: firstly on packaging machines, then when the product is opened by the user. In addition to these fundamental functions - presentation, preservation and machinability - there are now environmental, regulatory and public pressure constraints, as well as economic constraints.

Since there's no such thing as an ideal material with all the required qualities, the need to combine them quickly arose in this industry. This led to the development of laminates that first assembled materials such as cellulose film, paper, aluminum foil and thin plastic films of all kinds.

The first packaging converters tended to be small companies organized in a pyramidal structure around large producers of basic materials. With the advent of plastics and the emergence of increasingly high-performance polymers, this industry has now evolved considerably. It requires ever greater technical skills and increasingly sophisticated production resources. As a result, the sector is undergoing a transformation, and is now most frequently organized around large international groups.

This article provides an overview of a wide variety of these complex packaging materials in terms of :

• function (preservation and protection of packaged products) ;

• use (packaging techniques) ;

• production methods.

The reader will first learn about the different types of laminates, with numerous examples of the structures, applications and markets in which they are used.

This is followed by a description of the processes used to manufacture these materials, from the lamination (or complexing) processes originally used and now modernized, to the most advanced coextrusion processes which now make it possible to manufacture even thinner, higher-performance complex films or sheets in a single step from polymer resins.

The various techniques for packaging and preserving food products are then described in detail, to show the many ways in which they can be used and their impact on the products they package.

The article concludes with a reflection on the challenges facing producers of these materials.

Finally, a glossary closes the article. The reader will find a non-exhaustive but broadly representative list of the profession's technical vocabulary.