Plastic film

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Film strip

6 mil Polyethylene plastic sheet as vapor barrier in construction

Confectionery packaging made of PLA-blend bio-flex bioplastic

Shrink wrapped OH-58 Kiowa helicopters to be shipped.

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:

Polyethylene – The most common plastic film is made of one of the varieties of polyethylene; Low-density polyethylene, Medium-density polyethylene, High-density polyethylene, and Linear low-density polyethylene.
Polypropylene – Polypropylene can be made a cast film, biaxially oriented film (BOPP), or as a uniaxially oriented film.
Polyester – BoPET is a biaxially oriented polyester film
Nylon
Polyvinyl chloride – film can be with or without a Plasticizer
A variety of bioplastics and biodegradable plastics are available.
Semiembossed film – Semiembossed film can be used as a liner to the calendared rubber to retain the properties of rubber and also to prevent dust and other foreign matters from sticking to the rubber while calendaring and during storage

Processes

A tube of extruded film being blown to expand

Plastic films are usually thermoplastics and are formed by melting for forming the film.

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 lines stretch the extruded film before annealing.
Calender rolls can be used to form film from hot polymers
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
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 can have release agents applied as needed.

References

Standards by ASTM International

D882 – Standard Test Method for Tensile Properties of Thin Plastic Sheeting

D1004 – Standard Test Method for Tear Resistance (Graves Tear) of Plastic Film and Sheeting

D1204 – Standard Test Method for Linear Dimensional Changes of Nonrigid Thermoplastic Sheeting or Film at Elevated Temperature

D1593 – Standard Specification for Nonrigid Vinyl Chloride Plastic Film and Sheeting

D1709 – Standard Test Methods for Impact Resistance of Plastic Film by the Free Falling Dart Method

D1894 – Standard Test Method for Static and Kinetic Coefficients of Friction of Plastic Film and Sheeting

D1922 – Standard Test Method for Propagation Tear Resistance of Plastic Film and Thin Sheeting by Pendulum Method

D1938 – Standard Test Method for Tear Propagation Resistance of Plastic Film and Thin Sheeting by a Single Tear Method

D2103 – Standard Specification for Polyethylene Film and Sheeting

D2582 – Standard Test Method for Puncture Propagation Tear Resistance of Plastic Film and Thin Sheeting

D2673 – Standard Specification for Oriented Polypropylene Film

D2732 – Standard Test Method for Unrestrained Linear Thermal Shrinkage of Plastic Film and Sheeting

D2838 -Standard Test Method for Shrink Tension and Orientation Release Stress of Plastic Film and Thin Sheeting

D2923 – Standard Test Method for Rigidity of Polyolefin Film and Sheeting

D3420 – Standard Test Method for Pendulum Impact Resistance of Plastic Film

D3595 – Standard Specification for Polychlorotrifluoroethylene (PCTFE) Extruded Plastic Sheet and Film

D3664 – Standard Specification for Biaxially Oriented Polymeric Resin Film for Capacitors in Electrical Equipment

D3985 – Standard Test Method for Oxygen Gas Transmission Rate Through Plastic Film and Sheeting Using a Coulometric Sensor

D4321 – Standard Test Method for Package Yield of Plastic Film

D5047 – Standard Specification for Polyethylene Terephthalate Film and Sheeting

D6287 – Standard Practice for Cutting Film and Sheeting Test Specimens

D6988 – Standard Guide for Determination of Thickness of Plastic Film Test Specimens

E1870 – Standard Test Method for Odor and Taste Transfer from Polymeric Packaging Film

F2029- Standard Practices for Making Heatseals for Determination of Heatsealability of Flexible Webs as Measured by Seal Strength

F2622 – Standard Test Method for Oxygen Gas Transmission Rate Through Plastic Film and Sheeting Using Various Sensors

Books and general references

Hawkins, William E, The Plastic Film and Foil Web Handling Guide CRC Press 2003
Jenkins, W. A., and Osborn, K. R. Plastic Films: Technology and Packaging Applications, CRC Press 1992
Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, ISBN 978-0-470-08704-6

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