What Are Mylar Bags? The Complete Guide for 2026
What Is Mylar? Understanding the Material
Mylar is a brand name for BoPET (biaxially-oriented polyethylene terephthalate) film originally developed by DuPont in the 1950s. The term "mylar bag" now refers to any multi-layer barrier pouch using PET film as its structural base. According to Cubit Packaging, modern mylar bags use a tri-layer construction: PET exterior for strength and printability, aluminum foil middle layer for barrier performance, and PE (polyethylene) inner layer for heat-seal capability.
How Mylar Bags Work: The Barrier Science
The effectiveness of mylar bags comes from their multi-layer barrier construction. Each layer serves a specific purpose:
- PET (Polyethylene Terephthalate): The outer layer provides structural strength, puncture resistance, and a smooth surface for high-quality printing. BoPET film is stretched in two directions during manufacturing, creating exceptional tensile strength.
- Aluminum Foil: The middle layer is the key barrier element. Aluminum foil blocks 100% of light transmission and creates a near-perfect barrier against oxygen (OTR < 0.1 cc/m²/day) and moisture (WVTR < 0.01 g/m²/day).
- PE (Polyethylene): The inner layer provides food-safe contact surface and enables heat sealing. LLDPE (Linear Low-Density PE) is preferred for its superior seal strength.
Types of Mylar Bags
Mylar bags are available in several configurations, each designed for specific applications:
Stand-Up Pouches (Doypacks)
The most popular format, featuring a gusseted bottom that allows the bag to stand upright on retail shelves. Available with resealable zippers, clear windows, and child-resistant closures. Ideal for coffee, snacks, cannabis, and supplements.
Flat Mylar Bags
Three-side-sealed bags without a gusset. More compact and economical, these are ideal for, samples, sachets, and single-serve portions. Available with tear notches for easy opening.
Gusseted Bags
Side or bottom gussets expand to accommodate larger volumes. Popular for coffee (with degassing valve), pet food, and bulk products. Can include tin-tie closures.
Child-Resistant (CR) Bags
Specialized closure mechanisms (pinch-n-slide, press-to-close) certified to ASTM D3475 standards. Required for cannabis products in all legal US states and many pharmaceutical applications.
Mylar Bag Thickness Guide
Thickness is measured in mils (thousandths of an inch) or microns (µm). The right thickness depends on your product and storage duration:
| Thickness | Best For | Barrier Level |
|---|---|---|
| 2.5 mil (63 µm) | Sachets, samples, light snacks | Standard |
| 3.5 mil (89 µm) | Coffee, retail snacks, spices | Good |
| 5.0 mil (127 µm) | Cannabis, long-term food storage | High |
| 7.0 mil (178 µm) | Military MRE, industrial storage | Maximum |
Common Uses for Mylar Bags
Mylar bags serve a wide range of industries and applications:
- Long-term food storage: With oxygen absorbers, mylar bags preserve dry goods for 25-30 years
- Cannabis packaging: Child-resistant, smell-proof, and state-compliant options
- Coffee and tea: Degassing valve compatible with excellent aroma preservation
- Supplements and pharmaceuticals: GMP-ready packaging with moisture barriers
- Pet food and treats: Durable resealable pouches with heavy-duty construction
- Electronics: Anti-static and moisture protection for sensitive components
How to Choose the Right Mylar Bag
According to Cubit Packaging engineers, selecting the right mylar bag requires evaluating four key factors:
- Product type: Dry goods, liquids, or powders each require different barrier specifications
- Shelf life target: Short-term retail (3.5 mil) vs. long-term storage (5+ mil)
- Regulatory requirements: FDA compliance, child-resistant certification, state labeling
- Retail presentation: Stand-up for shelf display, flat for compact shipping, gusseted for volume
Mylar Bags vs. Other Packaging
Compared to standard plastic bags and paper packaging, mylar bags provide significantly superior barrier performance. Standard plastic bags offer no light protection and limited oxygen barriers, resulting in 1-2 year shelf life. Paper bags provide no moisture or oxygen barrier. Mylar bags with aluminum lamination block 100% of light and provide near-perfect gas barriers, extending shelf life to decades.
Ready to order custom mylar bags? Get a free quote from Cubit Packaging — MOQ 500 units with free design support.