Aluminum Foil vs. Metallized Polyester (MetPET) or Metallized Oriented Polypropylene (MetOPP) in Flexible Packaging: Which Is Right for Your Product?
Posted on August 1, 2025
In the world of flexible packaging, two popular barrier material types stand out: Aluminum foil and MetPET, or MetOPP. While both types offer excellent protection for sensitive products, they each come with distinct advantages that make them better suited for specific applications.
Aluminum Foil: The Ultimate Barrier
Aluminum foil remains the gold standard when it comes to barrier performance. It provides near-total protection from light, oxygen, moisture, and other environmental threats.
Key Benefits of Aluminum Foil:
- Excellent oxygen and moisture barrier
- Total light blockage
- Long shelf life for perishable or sensitive products
- Laminated structure with a thin layer of foil sandwiched between an outer strength layer and a sealing layer provides very strong seals, meaning a strong, reliable package.
Best Applications:
- Pharmaceutical pouches
- Medical devices
- Vacuum-packed foods (like coffee or dehydrated meals)
- Military and industrial use
MetPET or MetOPP: Lightweight, Cost-Effective Protection
MetPET & MetOPP are films coated with a thin layer of aluminum. It mimics many of foil’s barrier properties at a fraction of the weight and cost.
Key Benefits of Metallized PET or OPP:
- PET: good oxygen and moisture barrier (though lower than foil)
- OPP: very good moisture barrier, good oxygen barrier.
- PET/OPP: lightweight and flexible
- PET/OPP: lower cost per square foot
- PET: very high heat resistance and stiffness, making it excellent for high-speed converting and printing
- OPP: medium to high heat resistance with lower stiffness and good puncture resistance makes it ideal for packaging snack items like potato and tortilla chips.
- PET/OPP high abuse resistance, especially in, or near sealed areas
Best Applications:
- Snack food packaging
- Confectionery wrappers
- Pouches for dry goods
- Cosmetic and personal care sachets
- Single serve packets for coffee and similar items, designed for a short shelf life (weeks).
Head-to-Head Comparison
| Property | Aluminum Foil | Metallized PET | Metallized OPP |
| Barrier to Oxygen & Moisture | Outstanding | Good for both | Good Oxygen barrier Very good Moisture barrier |
| Light Transmission | 0% (Total Block) | Low (Depends on metal layer) | Low (Depends on metal layer) |
| Tear Resistance (propagation) | Adjustable, based on laminated substrates | Low – Medium | Medium |
| Flexibility | Adjustable, based on laminated substrates | Highly Flexible | Highly Flexible |
| Weight | Heavy | Lightweight | Lightweight |
| Cost | Higher | Lower | Lower |
| Seal Strength | High | Med | Med |
| Sealing “abuse” resistance | High (but sensitive to heat and pressure at extreme conditions) | Excellent | Very good |
Choosing the Right Material
If your product requires maximum protection and long shelf life, foil is the go-to. But if you’re looking for cost-efficiency, printability, and lighter handling, metallized PET or OPP may be the smarter option.
Need help determining which barrier film is best for your application?
Reach out to our experts directly at contactus@cadprod.com or 800-837-0055.