Metallised film


Metallised film
Metallised films used for food packaging

Metallised films (or metallized films) are polymer films coated with a thin layer of metal, usually aluminium. They offer the glossy metallic appearance of an aluminium foil at a reduced weight and cost. Metallised films are widely used for decorative purposes and food packaging, and also for speciality applications including insulation and electronics.

Contents

Manufacture

Metallisation is performed using a physical vapour deposition process. Aluminium is the most common metal used for deposition, but other metals such as nickel or chromium are also used. The metal is heated and evaporated under vacuum. This condenses on the cold polymer film, which is unwound near the metal vapour source. This coating is much thinner than a metal foil could be made, in the range of 0.5 micrometres [1]. This coating will not fade or discolour over time. While oriented polypropylene and PET are the most common films used for metallisation, nylon, polyethylene and cast polypropylene are also used [2].

Properties

Metallised films have a reflective silver surface similar to aluminium foil. The coating also reduces the permeability of the film to light, water and oxygen. The properties of the film remain, such as higher toughness, the ability to be heat sealed, and a lower density at a lower cost than an aluminium foil. This gives metallised films some advantages over aluminium foil and aluminium foil laminates. It was thought that metallised films would become a replacement for aluminium foil laminates, but current films still cannot match the barrier properties of foil. Some very high barrier metallised films are available using EVOH, but are not yet cost effective against foil laminates [3].

Table 1. Comparison of Metallised PET and aluminium foil

Moisture (g/m2.day) Oxygen (mL/m2.day) UV light (%transmittance)
PET film, 12.7μm [1] 31 465 91
Metallised PET [1] 0.8 1.2 5
Aluminium foil 6μm [4]. 0 0 0

Uses

Decoration

Metallised films used for balloons

Metallised films were first used for decorative purposes as Christmas tinsel [1], and continue to be used for items such as wrappers and ribbons. The metallic helium filled novelty balloons given as gifts are made of metallised PET.

Packaging

Both metallised PET and PP have replaced foil laminates for products such as snack foods, coffee and candy, which do not require the superior barrier of aluminium foil. Metallised nylon and polyethylene are used in the meat export market. The controlled permeation extends shelf life.

Metallised films are used as a susceptor for cooking in microwave ovens. An example is a microwave popcorn bag.

Many food items are also packaged using metallised films for appearance only, as these produce a package with greater sparkle when compared to competing products that use printed paper or polymer films.

Insulation

Metallised PET films are used in NASA's spacesuits to make them radiation resistant and keep astronauts warm, and in proximity (aluminized) suits are used by AR-FF fire fighters for protection from the high amount of heat released from fuel fires. Silvered emergency blankets are also used to conserve a shock victim's body heat. These reflective materials might also be used as part of industrial and commercial insulation (for example, insulated shipping containers.)

Insulating blankets made with Metallised PET were also used as insulation in aircraft until safety concerns resulted in their deprecation.[5] In particular, it was found to be a major cause of the in-flight fire of Swissair Flight 111 on September 2, 1998.[6]

Electronics

Metallised films are used as a dielectric in the manufacture of a type of capacitor used in electronic circuits.

See also

References

  1. ^ a b c d Hanlon, J. (1992). 1st ed. Handbook of Package Engineering, Lancaster, PA, Technomic Publishing: ISBN 0-87762-924-2. Chapter 4 Coatings and Laminations
  2. ^ Mount, E. (2004) Metallized Films for Food Packaging, Converting Magazine vol 3
  3. ^ Mount, E. (2002) Metallized Film Barriers: Where to Next? Converting Magazine vol 3
  4. ^ European Aluminium Foil Association
  5. ^ "Airworthiness Directive". FAA. http://www1.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/7157a2905d2a3e7286256a0800694ea9!OpenDocument&ExpandSection=-2. 
  6. ^ "Swissair to replace controversial Mylar insulation". CBC. 1999-11-09. http://www.cbc.ca/world/story/1999/11/09/swissair991109.html. Retrieved 2009-06-19. 

Further reading


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Plastics extrusion — Cross section of a plastic extruder to show the screw Plastics extrusion is a high volume manufacturing process in which raw plastic material is melted and formed into a continuous profile. Extrusion produces items such as pipe/tubing, weather… …   Wikipedia

  • Susceptor — A susceptor is a material used for its ability to absorb electromagnetic energy. This energy is typically radiofrequency or microwave radiation used in industrial heating processes, and also occasionally in microwave cooking. The name is derived… …   Wikipedia

  • Bag-In-Box — In packaging, a Bag In Box or BIB is a type of container for the storage and transportation of liquids. It consists of a strong (or plastic bag), usually made of metallised film or other plastics, seated inside a corrugated fiberboard box. The… …   Wikipedia

  • Overwrap — An Overwrap or wrap is applied over an item in a package or is applied over another form of packaging. It is often made of plastic film (sometimes called Polywrapping) or paper.[1] Contents 1 Functions 2 Types of Overwraps 2.1 …   Wikipedia

  • Vacuum deposition — Not to be confused with Vacuum coating. Vacuum deposition is a family of processes used to deposit layers atom by atom or molecule by molecule at sub atmospheric pressure (vacuum) on a solid surface. The layers may be as thin as one atom to… …   Wikipedia

  • Cutting stock problem — The cutting stock problem is an optimization problem, or more specifically, an integer linear programming problem. It arises from many applications in industry. Imagine that you work in a paper mill and you have a number of rolls of paper of… …   Wikipedia

  • Package testing — Military shipping container being drop tested Testing …   Wikipedia

  • Orbital stretch wrapping — An orbital stretch wrapper with motorized conveyor. Orbital stretch wrapping is a means of applying stretch film to a load consisting of a roll of stretch wrap supported on a vertical rotating ring and a means of passing a load through the ring s …   Wikipedia

  • Corrugated fiberboard — is a paper based material consisting of a fluted corrugated sheet and one or two flat linerboards. It is widely used in the manufacture of corrugated boxes and shipping containers. The corrugated medium and linerboard are made of containerboard,… …   Wikipedia

  • Shelf life — This pack of diced pork says display until 7 May and use by 8 May …   Wikipedia