Extrusion coating

Extrusion coating is the coating of a molten web of synthetic resin on to a substrate material. It is a versatile coating technique used for the economic application of various plastics, notably polyethylene, onto paperboard, corrugated fiberboard, paper, aluminium foils, cellulose or plastic films.

Process

Coating

The actual process of extrusion coating involves extruding resin from a slit die at temperatures up to 320°C directly onto the moving web which is then passed through a nip consisting of a rubber covered pressure roller and a chrome plated cooling roll. The later cools the molten film back into the solid state and also imparts the desired finish to the plastic surface.

Laminating

Extrusion laminating is a similar process except that the extruded hot molten resin acts as the bonding medium to a second web of material.

Co-extrusion

Co-extrusion is, again, a similar process but with two, or more, extruders coupled to a single die head in which the individually extruded melts are brought together and finally extruded as a multi-layer film.

Uses

The market for extrusion coating includes a variety of end-use applications such as: Liquid Packaging, Photographic, Flexible Packaging, and Commercial Applications (including among others: Mill and Industrial Wrappings, Transport Packaging, Sack Linings, Building, Envelopes, Medical/Hygiene and Release Base).

References

• Soroka, W, "Fundamentals of Packaging Technology", IoPP, 2002, ISBN 1-930268-25-4
• Gregory, B. H., "Extrusion Coating", Trafford, 2007, ISBN 978-1-4120-4072-3
• Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, ISBN 978-0-470-08704-6