Mylar® or BoPET: Manufacturing, Properties, Uses

Mylar®, also referred to as BoPET (biaxially-oriented polyethylene terephthalate), is a type of polyester film that is commonly used due to its superior mechanical and chemical qualities. It is so widespread that it is almost synonymous with all plastic films. It is a polyester film composed of stretched polyethylene terephthalate (PET), which is advantageous because of its exceptional strength, chemical and structural stability, transparency, reflectivity, gas and scent barrier qualities, and electrical insulation. 

Mylar® or BoPET Manufacturing, Properties, Uses
Mylar® or BoPET Manufacturing, Properties, Uses

The brand Mylar is used to recognize a specific kind of stretchable polyester film. The legally registered trademark Mylar®, which also denotes a certain line of plastic sheet goods, is made of polyethylene terephthalate (PET) and is owned by Dupont Teijin Films. The best general terms for this stuff are plastic sheets, polyester sheets, and polyester film. 

Interesting Science Videos

Discovery and Development of BoPET (Mylar®)

  • Midway through the 1950s, DuPont, Hoechst A.G., and Imperial Chemical Industries (ICI) started producing BoPET films.
  • The geodesic dome was created in 1953 by Buckminster Fuller with a group of University of Oregon students using Mylar to construct its exterior.
  • Mylar was originally used by Eastman Kodak in 1955 as an “ESTAR Base” support for photographic films.
  • The Echo II balloon was launched by NASA in 1964. The 40-meter-diameter Echo balloon was made of layers of 4.5-micrometer-thick aluminum foil in between 9-micrometer-thick Mylar film.

Manufacturing Process of Mylar

Let’s have a brief look at how the Mylar is manufactured. During the production or fabrication of mylar, the following processes are carried out:.

  • At the beginning of this process, polyethylene terephthalate (PET), a type of polymer, is heated and melted, allowing it to be poured into the rolling drum. This rolling drum is chilled so that it can harden the melted PET to form a film.
  • Secondly, the film goes into the stretching process to arrange the PET molecules so that the mechanical properties of the film are enhanced. During this process, the film undergoes stretching twice: once in the transversal (width) direction and once in the machine’s (or feed) direction. This is accomplished by running the film through a sequence of rollers and into a stenter frame, where it is transversely stretched.
  • Following the process, to maintain its structural integrity and prevent shrinkage at temperatures lower than the initial thermal threshold, the film is exposed to heat at around 200°C (392°F).
  • In the next stage of manufacturing, silicon dioxide (SiO2) coatings are commonly applied to Mylar materials to lessen stickiness. This is done to avoid the sticking of film layers because, after the completion of the above-mentioned steps, films get smoother and have the tendency to stick to themselves.
  • Moreover, Mylar can be physically vapor-deposited with evaporated gold (Au), aluminum (Al), or another metal to decrease transparency, raise reflectivity, and decrease gas permeability.

Properties of Mylar

In this section we will look at the different properties including physical, thermal, and electrical properties of Mylar®.

Physical Properties of Mylar®

PropertiesValue Test Method
Tensile Strength (MD)28000 psiASTM-D882
Tensile Strength (TD)34000 psiASTM-D882
Strength Elongation (MD)15000 psiASTM-D882
Strength F-5 TD14000 psiASTM-D882
Modulus (MD)710000 psiASTM-D882
Modulus (TD)740000 psiASTM-D882
Elongation (MD)115%ASTM-D882
Elongation (TD)92%ASTM-D882
Surface Roughness38 n/mOptical Profilometer
Density1.39 g/cm3ASTM-D1505
Viscosity0.56 dL/gASTM-D4603
Yield21000 lb/in2N/A

Different Chemical, Physical and Thermal Properties

  • Dimensional stability across a broad temperature range.
  • It is resistant to grease, oils, solvents, and moisture; it is also chemically inert.
  • It has a low permeability, which makes it useful as a barrier to most gases and liquids.
  • It is also a good electrical insulator with a high resistance to electricity of 1018 Ω⋅cm.
  • Its reflectivity improves both heat endurance and visual appeal when coated with metallic particles.
  • Mylar is transparent and may transmit 80–90% of radiation in the visible and infrared range when it is not coated with metallic particles.

Electrical Properties of Mylar®

PropertiesValueTest Method
Dielectric Strength AC (20º C, .00092″)7000 V/mASTM-D149-64
Dielectric Constant (25º C, 1kHz)3.2ASTM-D150-81
Dissipation Factor (25º C, 1kHz)0.005ASTM-D150-65
Volume Resistivity (25º C)1.00E+19 Ω·cmASTM-D257-78

Thermal Properties of Mylar®

PropertiesValueTest Method
Melting Point254 ºCN/A
Dimensional Stability at 105 ºC MD0.6%N/A
Dimensional Stability at 105 ºC TD0.3%N/A
Dimensional Stability at 150 ºC MD1.8%N/A
Dimensional Stability at 150 ºC TD1.0%N/A
Specific Heat0.28 cal/g °CN/A
Thermal Expansion1.7 x 10-5 °C-1ASTM-D696
UL-94 Flammability94 VTM-2slow to self extinguishing

Uses of Mylar®

Almost every application that needs a strong seal, resistant to heat and moisture, and tensile strength is compatible with Mylar® film. This product’s cost-effectiveness also makes it a top option across a wide range of sectors. Here’s our brief look at the important uses of this product.

Food Packaging Industries

  • The food packaging industry is one of the most Mylar-consuming sectors out there. 
  • Packaged products are shielded from impurities, moisture, and chemicals by the material’s strong adhesive and preservation properties, which prolong their shelf life.
  • Because it retains all of its original state and qualities even in extremely high temperatures, it is frequently used in frozen meals.
  • It is also used to lid the products which can be directly transferred from the fridge or freezer to the oven or microwave.

Glass Industry

  • Mylar® film possesses the ability to be laminated and coated with specific adhesives, resulting in window applications that are both scratch-resistant and protective.
  • Fitted window coatings made with polyester film are laminated and used in a range of industries.
  • Additionally, many window films are metalized for specific color and UV resistance qualities.

Electronic Displays

  • The majority of electronic displays in use today employ Mylar film.
  • Either diffusion coatings for the backlight mechanism or anti-glare or anti-reflection coatings are applied to the film.
  • The purpose of laminating this film to the display screen is to improve visibility in strong light.

Electronics Sector

  • Minor components for electronics capacitors are additionally produced from Mylar. These gadgets are used for collecting and storing electrical energy in an area of particular interest.
  • In these kinds of applications, Mylar is frequently utilized as an insulation between two metal components which carry electrical currents.
  • The material’s capacity to hold its shape despite the effects of heat and other environmental factors enables it to do this task very well.
  • Because this is a small component that only requires an insulating material, Mylar offers an affordable choice for this sort of application.

Insulation Materials

  • By sputtering a tiny layer of metal onto its surfaces, Mylar can be turned reflective or metalized. Mylar that reflects light has a bright side and a dull side, just like aluminum foil.
  • As it reflects up to 99 percent of light and is less prone to gas leakage, this particular variety of Mylar is frequently utilized in insulation.
  • Mylar should be placed inside a building in a cold environment with its shiny side facing inward to reflect heat that is escaping to warm the interior.
  • Mylar should be placed on the outside of a high-temperature area building with its shiny side facing outward to reflect heat from the sun and chill the interior.

Emergency Blankets

  • Mylar is used to regulate your body’s temperature in a similar way in which it is utilized to insulate buildings.
  • NASA pioneered the use of reflective emergency blankets, which retain a person’s body heat to their body.
  • These blankets are commonly employed for trauma victims as well as are often found inside wilderness emergency packs.
  • Using Mylar blankets to keep their body temperature from dropping too quickly afterward finishing the race has become more and more common among marathoners.

Musical Instruments

  • Drumheads, the thin material that covers one or both of a drum’s exposed sides, have been made from Mylar since the 1950s.
  • The Mylar material, when draped across the exterior of the drum, produces previously unachievable pitch, tone, and consistency.
  • Mylar drumheads are still widely used today and come in single- and double-ply varieties.


  • Mylar is a material commonly used in balloons. Mylar balloons often have a longer lifespan than latex balloons because they are made of plastic polyester, resulting in an airtight and impermeable setting that prevents helium from escaping.
  • Mylar holds its shape longer and may be molded into an infinite number of shapes, while latex balloons are more pliable and thinner after inflation.
  • The polyester film used in Mylar balloons can be coated with aluminum or another thin, bright metal. These reflecting balloons are also known as “foil balloons” due to their metal plating.

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Jyoti Bashyal

Jyoti Bashyal, a graduate of the Central Department of Chemistry, is an avid explorer of the molecular realm. Fueled by her fascination with chemical reactions and natural compounds, she navigates her field's complexities with precision and passion. Outside the lab, Jyoti is dedicated to making science accessible to all. She aspires to deepen audiences' understanding of the wonders of various scientific subjects and their impact on the world by sharing them with a wide range of readers through her writing.

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