Mylar vs Foil vs Poly Bags: Which Barrier Wins?

Three materials, three jobs

“Mylar”, “foil” and “poly” get used interchangeably, but they are different barriers. BoPET Mylar film is a strong, clear polyester film — usually metalized for light and oxygen resistance. Foil laminates add a true aluminum layer for the strongest barrier. Poly bags (PE or PP) are cheap, flexible, and protect against moisture and dirt but almost nothing else.

The barrier comparison

• Foil laminate — best oxygen, moisture and light barrier; the choice for coffee, herbs and long shelf life
• Metalized Mylar — near-foil barrier at lower cost; the standard for supplements and food samples
• Poly bags — moisture and dust protection only; fine for apparel and non-perishables
• Foil and Mylar are not resealable without a zipper or heat seal — plan the closure with the material

Where boxes fit

Flexible pouches protect contents but present poorly on a shelf and crush in a parcel. The combination most brands land on is a sealed pouch inside a printed folding carton or mailer: the pouch carries the barrier, the box carries the brand, the compliance panel and the shelf presence. We print the box; specify the pouch alongside it so the two are sized to fit.