Thin continuous polymeric material
6 mil polyethylene plastic sheet as vapor barrier in construction
Plastic film is a thin continuous polymeric material. Thicker plastic material is often called a "sheet". These thin plastic membranes are used to separate areas or volumes, to hold items, to act as barriers, or as printable surfaces.
Plastic films are used in a wide variety of applications. These include: packaging, plastic bags, labels, building construction, landscaping, electrical fabrication, photographic film, film stock for movies, video tape, etc.
Materials
Almost all plastics can be formed into a thin film. Some of the primary ones are:
Processes
A tube of extruded film being blown to expand
Plastic films are usually thermoplastics and are formed by melting for forming the film.[2]
- Cast – Plastics extrusion can cast film which is cooled or quenched then wound up on a roll.
- Extruded film can be stretched, thinned, or oriented in one or two directions. Blown or tubular process forces air into an extruded ring to expand the film. Flat tenter frames stretch the extruded film before annealing.[3]
- Calender rolls can be used to form film from hot polymers[4]
- Solution deposition is another film forming process.
- Skiving is used to scrape off a film from a solid core (sometimes used to make PTFE thread seal tape)
- Coextrusion involves extruding two or more layers of dissimilar polymers into a single film
- Lamination combines two or more films (or other materials) into a sandwich.[5]
- Extrusion coating is used to form a film onto another film or substrate
Further processing
Plastic films are typically formed into rolls by roll slitting. Often additional coating or printing operations are also used. Films can be modified by physical vapor deposition to make metallised films. Films can be subjected to corona treatment or plasma processing; films can have release agents applied as needed.
