MYLAR - Polyester film (PET)
MYLAR A® is a transparent, flexible polyester film based on polyethylene terephthalate, which becomes milky and less transparent with increasing thickness (over 190 μm). The Mylar film is obtained by condensation between ethylene glycol and terephthalic acid.
Mylar film - applications
What distinguishes Mylar film is its excellent electrical, chemical and physical properties. Thanks to them, Mylar film is widely accepted in all markets, industry and other applications where polyester film is required. Its excellent dielectric properties make it particularly suitable for electrical insulation applications in machinery up to Class B (130°C), as internal protection for cables, and as a component for adhesive tapes and electrical insulation laminates. In transformers, Mylar film is used as core, layer and surface insulation.
Mylar film is not only used in electrical engineering - it is used as an industrial laminate and is also used in the woodworking industry (e.g. in joinery presses).
Mylar film - properties
A uniquely advantageous feature of Mylar films is the very slight decrease in dielectric strength with increasing temperature and its small decrease with increasing humidity. In addition, on average, this material has a strength of 210 MPa and a density of 1.39 g/cm3.
PET films have excellent resistance to moisture and commonly used solvents. They come in thicknesses of [μm]: 19, 23, 36, 50, 75, 100, 125, 190, 250, 300, 350, 420, 500. The performance of Mylar film largely depends on the thickness - among other things, its dielectric strength increases with thickness, being 13.5 kV for 125 μm thick Mylar film and 20 kV for 500 μm thick Mylar film, respectively.
Below, we have summarised the most important mechanical and electrical properties of Mylar films for thicknesses of 125 and 500 μm (values marked according to ASTM standards):
|Parameter||Mylar 125 μm||Mylar 500 μm|
|tensile strength [MPa]||220||170|
|modulus of elasticity [GPa]||3,7||2,8|
|shrinkage at 150°C for 30 min. [%]||1,3||0,9|
|minimum dielectric strength [kV]||13,5||20|
Mylar® Melinex is a registered trademark of DuPont®.