What are the properties of polyester film?
Polyester or polyethylene terephthalate (PET) is a high-performance, crystal-clear thermoplastic made from ethylene glycol and dimethyl terephthalate (DMT). Compared to other common plastic films, PET film has higher tensile strength, excellent dimensional stability, low moisture absorption and good retention of physical properties over a wide temperature range.
It also has excellent UV resistance, excellent electrical properties, good optical clarity, high gloss and good gas barrier properties, but only moderate moisture resistance.
It is an ideal film for high quality printing and laminating processes, as well as for high performance plastic films and sheets. It has a high melting point, making it suitable for applications that require autoclaving.
What are the applications of polyester film?
PET film can be metallized for improved gas barrier properties for demanding applications where long product shelf life is required. PET film is suitable for a variety of industrial, electronic and automotive applications. It is fully recyclable and can be easily converted into many other products for various applications.
Unlike paper and other cellulosic products, however, PET does not break down easily. However, there are biodegradable additives that can improve the biodegradability of this plastic without affecting its physical properties.
The most important polyester films are biaxially oriented PET or BOPET. Compared to other common plastic films, it retains its physical properties over a relatively wide temperature range of about -70 °C to 100 °C.
Despite its higher price, BOPET has found many high-volume applications that require this stronger and dimensionally stable film.
A major disadvantage of BOPET is its higher manufacturing cost and equipment investment.
PET film in use
PET film is often an excellent choice for more demanding food and non-food applications. The main applications of polyester film include:
- Microwave and medical packaging,
- Plastic film,
- printed film,
- plastic cards,
- Protective coatings such as solar and safety window films,
- Release films,
- Transformer insulation film u
- Flexible printed circuit boards.
PET is also used as a flavor barrier film (e.g., in coffee and tobacco packaging). Films of this type are sometimes metallized by vapor deposition of metals, which further improves the barrier to oxygen, water vapor and flavor loss.
Low odor, high chemical resistance and inertness make many PET grades suitable for packaging applications subject to FDA regulations.
Mylar films come in many types, thicknesses and widths with properties tailored to the specific requirements of specific end-uses.
For information on the different brands of polyester films, see our article "Mylar Brands: Mylar, Hostaphan, Melinex, Lumirror and Garware."
PEN (polyethylene naphthalate)
What are the properties of PEN films?
Polyethylene naphthalate (PEN) is a semi-aromatic transparent polyester synthesized from naphthalene-2,6-dicarboxylic acid and ethylene glycol. Compared to PET, it has lower oxygen permeability, better hydrolysis resistance, higher tensile strength and service temperature due to its higher glass transition temperature (120 °C versus 75 °C) and lower elongation and shrinkage. PEN generally outperforms PET in high-end applications in terms of requirements and is generally a good and lower cost alternative to polyimide, with properties between polyester and high-performance polyimide.
What are the applications of PEN film?
PEN is commonly used in film applications. Some examples are
- Flexible printed circuits,
- Insulating films in transformers,
- Laminate u
- Optical display.
Due to its low oxygen permeability, it is especially suitable for oxidation-sensitive products. PEN is also used as a high performance fiber, it has a very high modulus and better dimensional stability than other polyester or nylon fibers.
The best known brand for PEN membranes is the "Teonex" brand. The previous brand name was "Kaladex".
How do PEN and PET films differ in terms of processing?
Both technical films can be cut, punched, formed and coated very well. Spring strips for transformer construction can also be made from both sheets.
What is the main difference between PEN and PET?
PEN differs from PET in more airtightness and dimensional stability, as well as mechanical values (Young's modulus, strength) and increased resistance to chemicals, UV and pyrolysis. On the other hand, the bending life is lower and the cost is higher than polyester film. The
PEN membrane has many outstanding properties such as strength, heat resistance, hydrolysis resistance, dimensional stability and low oligomer extraction. Because of these performance characteristics, PEN film has the potential to be substituted for other technical films such as polyimide films, with additional cost benefits. PEN film also has good machinability properties (similar to polyester film).