How is Mylar made

Mylar is a brand name of the DuPont company for a polyethylene terephthalate polyester film (BOPET: biaxially-oriented polyethylene terephthalate).

Mylar is characterized above all by its high tensile strength, chemical, mechanical and thermal stability and transparency. Mylar is a good electrical insulator, it has a low water absorption (0.3%) and an electrical dielectric strength of about 133 V / µm [1]. Mylar is the lightest and highest strength film that can be made. It weighs 10 to 11 g / m², depending on the coating.

Several companies manufacture BOPET and other polyester films under different brand names, but Mylar is often used as a generic term.

History and manufacturing process

Mylar was developed by DuPont in the mid-1950s. The "Echo" satellite launched by NASA in 1961 was a balloon made of 0.127 mm (5 mil) thick, metal-coated Mylar foil with a diameter of around 30 m.

Mylar is made by applying a thin layer of molten PET to a roller and then stretching it orthogonally to the direction of rotation of the roller. One side is now smooth, the other is rough, and can be printed or coated.

Mylar can be coated with aluminum by sputtering. The product has a significantly lower gas permeability (important for food packaging) and reflects up to 99% of the light including a large part of the infrared spectrum. Like aluminum foil, aluminized Mylar also has a matt and a glossy side. Mylar is very tear-resistant, in contrast to tinfoil and aluminum foil. Due to its reflective properties, it can be used for thermal insulation and, for example, also for solar observation: it is used in those glasses that are used for observing solar eclipses. The aluminum layer is a good reflector, especially for the infrared radiation from the sun, but allows fractions of a percentage of the visible light to pass through. Caution is advised, however, because hairline cracks in the aluminum layer that cannot be seen with the naked eye can reduce the effectiveness of these films over time.



  • Electrical insulating material
  • Thermal insulation material (e.g. in rescue blankets or tents)
  • Covering food containers (including microwave and oven-safe)
  • as a reflective ornament on books, cards or art prints
  • for document envelopes (e.g. for archiving purposes)
  • as a cover sheet for non-destructive use and labeling of maps
  • Dielectric in film capacitors and as a base material for flexible printed circuit boards
  • Sun sail (e.g. Cosmos 1)
  • Balloons; especially when coated with metal, it has a significantly lower helium permeability than rubber
  • Base substrate for magnetic tapes (e.g. VHS or audio cassettes)
  • as membranes for electrostatic loudspeakers, condenser and electret microphones
  • 5 Mylar layers are incorporated into NASA spacesuits to provide thermal insulation and gas tightness
  • For the manufacture of drum heads, see

Category: Plastic