Yes, metallized Mylar can reflect infrared radiation because it has a thin aluminum coating. This reflective layer redirects radiant heat instead of absorbing it, which is why Mylar is often used in thermal blankets, insulation barriers, and reflective packaging materials.

Mylar has excellent reflective characteristics, which give it a multitude of applications for packing, insulating, and protecting against environmental agents. Many people ask if Mylar can block infrared radiation. 

Knowing more about how Mylar works can help explain the various uses of Mylar for items such as thermal blankets and protective packaging.

"The material is very efficient in reflecting infrared rays… which is why Mylar is commonly used in thermal blankets and spacecraft insulation." - Kemp USA

The Short Answer

Metallized Mylar can block or reflect infrared radiation. The thin aluminum layer on metallized Mylar reflects radiant heat instead of absorbing it, which helps reduce heat transfer. Plain Mylar (uncoated PET film) does not block infrared as effectively because it lacks the reflective metal layer.

Mylar Explanation

Mylar refers to biaxially oriented polyethylene terephthalate (PET) film and is a brand name of DuPont. This type of polyester film is made by stretching it in both directions while manufacturing to give it extra strength, stability, and barrier properties. Unless PET film is treated in some way, it will be transparent and will not strongly block infrared radiation. Most people associate Mylar's ability to resist infrared radiation with the use of metallized coated films. 

The majority of Mylar films are coated with an extremely thin layer of aluminum, which creates a reflective surface to reflect all types of radiant energy, including those associated with infrared waves. The reason for the heat-resistant nature of the reflectivity of the metallized layer is because radiant energy has the ability to transmit heat when it is emitted as infrared radiation.

What is Infrared Radiation?

Infrared radiation is found on the electromagnetic spectrum just beyond red visible light. It is not visible to the human eye but is felt as heat. When an object is heated, it produces infrared energy that can move through the atmosphere as radiant heat.

When infrared radiation strikes an object, it can do one of these three things:

1. Absorb or take in the infrared radiation
2. Penetrate through the object
3. Reflect away from the object

Because metallized mylar reflects back much of the infrared energy instead of absorbing it like other materials, they make great choices for use in thermal insulation and reflective barriers.

Why Metallized Mylar Reflects Heat

Metallized Mylar contains an aluminum layer which has reflective properties. Metals typically reflect radiant energy as opposed to allowing radiant energy to pass through. Thus, the aluminum coating, despite being extremely thin, will reflect a substantial portion of infrared radiation.

These reflective properties are why Mylar is utilized for items such as:

Thermal emergency blankets
Reflective insulation
Greenhouses that reflect light
Heat shielding products
Protective packaging

In all cases, reflected film redirects radiant heat rather than transmitting radiant heat through the surface.

Does All Mylar Block Infrared?

Not all Mylar behaves the same way. The infrared blocking ability depends on the structure of the film.

Plain polyester film without metal coating does not strongly reflect infrared radiation. It may allow a portion of infrared energy to pass through. Metallized Mylar, however, reflects a much larger percentage because of the aluminum layer.

Thickness, coating type, and layering also affect performance. Some multilayer barrier films combine metallized polyester with additional materials to improve heat reflection and insulation.

The use of Mylar in Packaging

Mylar has many advantages over other plastic films in that it has good barrier properties (to oxygen, moisture & light), but its primary purpose in most applications is not the use of IR-reflective films, rather they used as an added value to the product as a method of assisting in reducing heat during the product's life cycle.

For products that are sensitive to heat or light, reflective films can provide additional protection during storage and transportation. Many companies rely on custom packaging Mylar bags to help preserve freshness and reduce environmental exposure throughout the product’s lifecycle.

Conclusion