What Is Polyester Film?
Polyester film is known for several characteristics which are unique and incomparable among many components in today's industries. This type of component is made from polyethylene terephthalate or PET. Polyester film is popular for its high tensile strength. It also has dimensional and chemical stability ideal for many industrial functions. Its reflectivity along with aroma and gas barrier makes it an even more versatile component. Polyester film is also good for electrical insulation.
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History
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PET (polyethylene terephthalate) is patented under the names of James Tennant Dickson and John Rex Whinfield in 1941. Tennant and Whinfield are both British chemists who previously worked under Calico Printer's Association of Manchester. Their discovery of PET is the product of their continued research started by Wallace Carothers. As many people today know, PET is the base component from which polyester film is made from. Both researchers found that the research conducted by Carother had not examined the formation of polyester from terephthalic acid and ethylene glycol.
Manufacturing
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Polyester film goes through different manufacturing processes before it can be used as such. The production procedure starts with a film of molten polyethylene terephthalate. This firm is extruded on top of a chill roll. In turn, this roll presses it until it reaches an amorphous state. Drawing is used to give the film a biaxial orientation. Commonly this is done through is through a sequential process wherein the film gets initially dram into the machine. It goes through heated rollers and further processed in the transverse direction.
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Crystallization
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After drawing, the film is subjected to crystallization or "heat set." That is, the film is put under tension and placed inside the oven. The ideal oven temperature should be more than 200 °C. Heat setting is very important in the production of polyester film because it helps prevent the film from going back or shrinking to its initial "crumpled" shape. Crystallization or heat setting also helps secure the molecular orientation. The molecular orientation of the polymers gives the film its stiff and strong quality. Lastly, the heat setting procedure is also responsible for the clear nature of the film although it has a semi-crystalline structure.
Additional Processes
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Given that the polyester film is manufactured without the use of additives, the film's surface will definitely be smooth and the layers would go strongly with one another. Similarly, the polyester films will mimic just how clean glass plates appear when stacked together. For more convenient handling, microscopic inert inorganic particles are often inserted in the PET. This, in turn, makes the film's surface rougher. The resulting film can be used in many different ways and in many different industries.
Application
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Polyester film has many different applications. It can be used for food packaging as well as food contact applications. When food products are stored inside packaging setups made from polyester film, they tend to have longer shelf life. Polyester film is also used as additional covering for different types of documents. Some of these include maps and other duplicated materials. Other applications include: as insulating material, for solar and marine applications and even graphic arts.
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