Polyester Films

Properties

Polyester or polyethylene terephthalate (PET) is a high-performance, crystal clear thermoplastic made from ethylene glycol and dimethyl terephthalate (DMT). In comparison with other common plastic films, PET film has higher tensile strength, excellent dimensional stability, low moisture absorption, and good retention of physical properties over a fairly wide temperature range. It also has superior UV resistance, excellent electrical properties, good optical clarity, high gloss, and good gas barrier but only moderate moisture barrier properties. It is the ideal film for quality printing and lamination and a good choice for a high performance plastic films and sheets. It has a relative high melting point, which makes it suitable for applications that require sterilization at high temperatures.

Because of its higher price relative to PVC, PE, and PP film, it is generally considered a specialty film.

PET can be metallized which results in improved gas barrier properties for demanding applications where long product shelf life is important. PET film is well suited for a broad range of industrial, electronic, and automotive applications. It is fully recyclable and can be easily reprocessed into many other products for many different applications. However, unlike paper and other cellulose products, PET does not readily decompose. However, biodegradable additives are available that enhance the biodegradation of this plastic without affecting the physical properties.

The most important polyester film is biaxially oriented PET or BOPET.¹ In comparison to other common plastic films, it has better retention of physical properties over a fairly 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 drawback of BOPET is the higher manufacturing costs and higher capital investment in equipment.

Applications

PET film is often an excellent choice for more demanding applications in food and nonfood-film applications. Major uses include microwave, and medical packaging, plastic wrap, tape backing, printed films, plastic cards, protective coatings such as solar and safety window films, release films, transformer insulation films and flexible printed circuits. PET is also used as an aroma barrier film (e.g. coffee and tobacco packaging). This type of film is sometimes metallized by vapor deposition of metals, which further improves the barrier against oxygen, water vapor and aroma loss. 

Due to the low odor, high chemical resistance and inertness, many PET grades are suitable for packaging applications under FDA regulations.

Polyester film is sold in various types, thicknesses, widths with properties tailored to meet specific requirements of particular end uses.

¹”Biaxially oriented" means that the PET film is stretched in two different directions to increase strength and modulus (lower elongation and higher stiffness).