Extrusion coating is the coating of a molten web of synthetic resin

Synthetic resin

Synthetic resins are materials with a property of interest that is similar to natural plant resins: they are viscous liquids that are capable of hardening permanently. Otherwise, chemically they are very different from the various resinous compounds secreted by plants .The synthetics are of several...

 on to a substrate material. It is a versatile coating technique used for the economic application of various plastics, notably polyethylene

Polyethylene

Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...

, onto paperboard

Paperboard

Paperboard is a thick paper based material. While there is no rigid differentiation between paper and paperboard, paperboard is generally thicker than paper. According to ISO standards, paperboard is a paper with a basis weight above 224 g/m2, but there are exceptions. Paperboard can be single...

, corrugated fiberboard, paper

Paper

Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....

, aluminium foil

Aluminium foil

Aluminium foil is aluminium prepared in thin metal leaves, with a thickness less than , thinner gauges down to are also commonly used. In the USA, foils are commonly gauged in mils. Standard household foil is typically thick and heavy duty household foil is typically .The foil is pliable, and...

s, cellulose

Cellulose

Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

 or plastic films

Plastic wrap

Plastic wrap, cling film , cling wrap or food wrap, is a thin plastic film typically used for sealing food items in containers to keep them fresh over a longer period of time...

.

Coating

The actual process of extrusion coating involves extruding resin from a slit die

Die (manufacturing)

A die is a specialized tool used in manufacturing industries to cut or shape material using a press. Like molds, dies are generally customized to the item they are used to create...

 at temperatures up to 320°C directly onto the moving web which is then passed through a nip consisting of a rubber

Elastomer

An elastomer is a polymer with the property of viscoelasticity , generally having notably low Young's modulus and high yield strain compared with other materials. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber, although the latter is preferred...

 covered pressure roller and a chrome plated

Chrome plating

Chrome plating, often referred to simply as chrome, is a technique of electroplating a thin layer of chromium onto a metal object. The chromed layer can be decorative, provide corrosion resistance, ease cleaning procedures, or increase surface hardness.-Process:A component to be chrome plated will...

 cooling roll. The latter 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

Adhesive

An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials...

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).