Mylar Bag Material Explained: PET, AL, PE and High Barrier Film Structure

What Is a Mylar Bag Made Of?

A mylar bag is usually made from laminated film, which means several material layers are combined together to create one flexible packaging structure.

A common structure is:

PET / AL / PE

Each layer has a different function:

• PET: outer layer for printing, strength, and durability
• AL: aluminum layer for barrier protection
• PE: inner layer for heat sealing and product contact

This multi-layer design helps mylar bags provide better protection than simple plastic bags. It can improve resistance against moisture, oxygen, light, odor, and external contamination.

For retail brands, choosing the right mylar bag material is important because it affects packaging appearance, shelf life, sealing performance, and customer experience.

PET Layer: Printing, Strength and Durability

PET, also known as polyethylene terephthalate, is commonly used as the outer layer of mylar bags.

The PET layer plays an important role in packaging appearance and structure. It provides a smooth surface for printing and helps the bag maintain better strength during production, filling, shipping, and retail display.

Main functions of PET:

• Provides a printable outer surface
• Improves bag strength and stiffness
• Helps maintain packaging shape
• Supports matte or glossy surface finish
• Protects the printed artwork
• Improves durability during handling

For custom printed mylar bags, the PET layer is very important because it affects how sharp and stable the artwork looks.

If your packaging requires full-color printing, custom logo design, matte finish, glossy finish, spot UV, or holographic effect, the PET layer helps support the final visual result.

AL Layer: Light, Oxygen and Moisture Barrier

AL refers to aluminum foil or aluminum-based barrier material. This layer is usually placed in the middle of the mylar bag structure.

The AL layer is one of the most important reasons why many brands choose mylar bags. It helps block light, oxygen, moisture, and odor transfer, making the bag suitable for products that need stronger freshness protection.

Main functions of AL:

• Blocks light transmission
• Improves oxygen barrier
• Helps reduce moisture exposure
• Supports smell-proof performance
• Protects product freshness
• Improves long-term storage performance

For products that are sensitive to light, air, humidity, or aroma loss, the AL layer can significantly improve packaging protection.

This is why many smell proof mylar bags and high-barrier flexible packaging designs use aluminum-based laminated structures.

PE Layer: Heat Sealing and Inner Contact Layer

PE, or polyethylene, is commonly used as the inner layer of mylar bags.

The PE layer is responsible for sealing performance. During production, the bag edges are heat sealed, and the PE layer melts and bonds together to create a secure seal.

Main functions of PE:

• Provides heat sealing performance
• Forms the inner product contact layer
• Supports flexibility
• Helps create strong sealed edges
• Works with zipper closure systems
• Improves bag durability during use

A good PE layer helps the bag stay sealed during storage, shipping, and repeated handling. It is also important for resealable zipper bags, stand-up pouches, flat pouches, and child-resistant mylar bags.

If the PE layer is not suitable for the bag structure, the packaging may have weak sealing, poor flexibility, or unstable edge strength.