PET Film
Tape Data Recovery - PET Film
Biaxially-oriented polyethylene terephthalate (boPET) is a polyester film originally developed by DuPont and Imperial Chemical Industries. Several companies now manufacture boPET and other polyester films under different brand names. The most popular brands in the Western markets are Mylar and Melinex.
BoPET films have high tensile strength, as well as chemical and dimensional stability. They have a typical Young’s modulus of about 4 Gpa. The orientation of the polymer chains is responsible for their high tensile strength and stiffness. Their molecular orientation induces the formation of many crystal nuclei. These crystallites reach the boundary of the neighboring crystallites and remain smaller than the wavelength of visible light. As a result, biaxially oriented PET film has excellent clarity, despite its semicrystalline structure.
Manufacturing Process
A film of molten polyethylene terephthalate (PET) is extruded on to a chill roll, which changes it into an amorphous state. This is then biaxially oriented by drawing. After the completion of this process, the film is ‘heat set’ in the oven at temperatures typically above 200oC. This method prevents the film from shrinking back to its unstretched shape.
Uses
BoPET are used in a variety of applications including scientific, acoustic and electronic industries. For example, NASA used boPET film in their Echo satellites which were launched in 1960 and 1964. In electronics, they are used as carrier for flexible printed circuits and as diaphragm material in electrostatic loudspeakers and microphones. It is also used as substrate magnetic recording tapes and floppy disks. boPETs are also used in flexible packaging and as electrical insulations.
