Plastic film
Plastic film , also known colloquially as plastic film or polymer film , is a thin sheet of plastic (typically 2 µm to 0.5 mm wall thickness) . It is first made in endless strips, rolled up and later cut into suitable pieces. Thinner material is called a membrane, thicker material cannot be rolled up and is called a board .
Base material
Plastic films often consist of polyolefins such as high and low density polyethylene (PE) or polypropylene (PP). In addition, polyvinyl chloride (PVC), polystyrene (PS), various polyesters and polycarbonate (PC) are also suitable . On the other hand, cellophane is made from cellulose (process analogous to viscose , but from slot nozzles), but can be coated with plastic film. Other bio-based plastics such as polylactide (PLA), cellulose acetate and starch blends can also be processed into films and are used accordingly. Polyethylene terephthalate (PET) is used for high-quality films.
Multi-layer composites are often made from a combination of different plastics. This allows certain properties, such as the permeation behavior , to be improved.
The production of polycarbonate film was discontinued in 2000 because the small production volume with the plastic film capacitor as the sole application became uneconomical.
properties
The main characteristic of plastic films is their ability to be wrapped on or around objects and to adapt to their shape. Typical film thicknesses are in the range below 0.1 millimeters. As electrical insulation foils, they can sometimes be only 0.002 millimeters thick. The tear strength is between 20 and 300 N / mm², depending on the material, but is often different along and across the extrusion direction. The elongation at break can easily reach several hundred percent.
Plastic films can be colored in many colors, but with some materials they can also be made completely transparent . In this case one also speaks of cling film .
They are mostly electrically insulating , but are made conductive by modifiers, especially for the packaging of statically sensitive electronic components.
The mechanical resilience can be increased by reinforcing with glass fibers or adding a braid . Certain polymers or additives also increase the thermal load capacity, for example in films for photocopiers or laser printers .
Manufacturing
Plastic films are mostly produced by extrusion (see also coex film ). In addition, they can also be manufactured by casting , calendering or blow molding .
use
Plastic films are often used as packaging , the covering of building materials and the (mostly temporary) lining of openings. Other construction foils are used to isolate different layers. In geotechnical engineering , so-called geotextiles are used, with which subterranean layers are isolated from one another or - for example in landfills - are also used to collect the landfill gases .
Adhesive-coated PVC films are used for digital printing and as cutting film. They are sold in rolls and in advertising technology for the production of signs, labels outdoors , vehicle wraps used and surface protection.
Special, breathable, self-adhesive films are used as wound dressings in the context of moist wound treatment .
Transparent foils ( cling foils ) serve as carrier material for writable overhead foils for overhead projectors or for the light-sensitive layer of films .
Films are also used in agriculture ( film culture ).
Plastic film products
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Web links
Individual evidence
- ^ Nentwig, Joachim: Plastic films: production, properties, application . 3. Edition. Carl Hanser Verlag, Munich 2006, ISBN 978-3-446-40390-1 , p. 33 ( hanser.de [PDF]).