What are plastic films?
Plastic film is a thin sheet of material with a thickness less than 2.5mm/10 mils/1000 gauge, averaging between 0.7 mils to 1.5 mils. It is (usually plastic and transparent) used as a packaging medium to cover or wrap things. A mil is 0.00l inch.
Plastic film also can be clear or colored, printed or plain, single- or multilayered and combined with other materials such as aluminium and paper.
How it is made?
- Extrusion - hot, melted plastic resin is forced through a circular die, forming a thin tube. Air is introduced, expanding the size of the cooling tube which is then flattened as it passes through converging slats and rollers.
- Extrusion coating - resin is melted and forced through a long, slit-shaped die. The sheet of plastic falls evenly onto a continually moving roll of material, such as paper, cardboard, aluminium foil or fabric. The plastic cools and sets on the material.
- Coextrusion - this involves complex die design and multiple extruders, allowing two or more melt streams to be combined. Increasingly, up to five or seven layers are now being used.
- Calendering - this process follows the principle of squeezing laundry out in an old mangle. Hot plastic is poured and evenly squeezed between rollers.
The benefits of plastic film
The use of plastic film has grown steadily over time. According to data compiled by SPI, only 8,690 million pounds of plastic were used to manufacture film in 1990; by 1994, that number had increased nearly 20 percent, to 10,375 million pounds. A brief discussion of some of the benefits of using plastic film, all of which have contributed to its recent growth in packaging applications, follows.
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