January 30, 2026
Flexible packaging's performance is fundamentally defined by its component films. Each material brings unique properties to the laminate structure. Here is a detailed guide to the primary films used, categorized by their core function in the packaging structure.
A typical high-performance flexible laminate consists of three functional layers:
Outer Layer: Provides structure, printability, and abrasion resistance.
Middle Layer (Barrier): Imparts critical gas, aroma, or moisture barrier.
Inner Layer (Sealant): Enables heat sealing and offers product compatibility.
These films form the package's backbone, offering durability and a printable surface.
Full Name: Biaxially Oriented Polyethylene Terephthalate.
Key Properties:
High tensile strength and rigidity, excellent dimensional stability.
Brilliant clarity and gloss for superior graphics.
Good barrier to gases and aromas, fair moisture barrier.
Excellent printability and lamination adhesion.
Temperature resistant (up to ~150°C).
Primary Role: Outer layer for pouches, lidding, and as a base for metallization.
Common Gauges: 12µm, 12µm, 23µm.
Key Properties:
Excellent moisture barrier (best among common plastics).
Good clarity and gloss, lower cost than PET.
Good stiffness and puncture resistance.
Lower heat resistance than PET.
Primary Role: Outer layer for snack bags, confectionery overwrap, label films.
Variants: Pearlescent OPP (for aesthetic effect), Metallized OPP (enhanced barrier).
Common Gauges: 20µm, 25µm, 30µm.
Key Properties:
Exceptional toughness, puncture, and abrasion resistance.
Good oxygen barrier (when dry), excellent aroma barrier.
Poor moisture barrier – properties degrade with humidity.
Primary Role: Middle or outer layer in packaging for sharp, heavy, or fatty products (e.g., pet food, cheese, frozen meat).
Common Form: Biaxially oriented (BOPA).
Common Gauges: 15µm, 20µm.
These specialized films protect the product from oxygen, moisture, light, or aromas.
Key Properties:
Absolute barrier to gases, moisture, light, and microorganisms.
Provides a distinctive metallic appearance.
Pinholes can occur at thin gauges, compromising barrier.
Primary Role: The ultimate barrier layer in retort pouches, aseptic packaging, and high-value dry foods.
Limitation: Not transparent, non-microwaveable, and makes the package non-recyclable in standard streams.
Common Gauges: 6µm, 7µm, 9µm.
Process: A thin layer of aluminum (< 1 µm) is vacuum-deposited onto a film substrate (PET, CPP, BOPP).
Key Properties:
Very high barrier to gases and moisture (though not absolute like foil).
Excellent light barrier, conductive for static dissipation.
Retains some flexibility and is more cost-effective than foil lamination.
Primary Role: High-barrier packaging for coffee, snacks, and dried foods where an absolute barrier isn't required.
Common Structure: VMPET (e.g., 12µm PET with metallization) is the industry standard for high-barrier laminates.
Key Properties:
Exceptional oxygen barrier (10-100x better than typical films) – but only when dry.
Barrier properties drop significantly at high humidity.
Must be co-extruded between protective layers (like PE or PP) to function.
Primary Role: The primary oxygen barrier in "transparent high-barrier" packaging (e.g., liquid pouches, vacuum bags). It is sandwiched as a middle layer.
Sustainability Note: Enables all-PE or all-PP recyclable structures with high oxygen barrier.
Process: Ultra-thin ceramic layers applied via vacuum deposition.
Key Properties:
Transparent high barrier to oxygen and moisture.
Excellent retort and microwave suitability.
More brittle than metallized films, can suffer from micro-cracking.
Primary Role: Transparent high-barrier packaging for premium products (e.g., baby food, medical devices) and microwaveable retort meals.
These polyolefin-based films form the innermost layer, creating the hermetic seal.
Types:
LDPE (Low-Density PE): Excellent clarity, good sealing range, low heat resistance.
LLDPE (Linear-Low-Density PE): Superior seal strength, puncture resistance, and flexibility.
MDPE/HDPE (Medium/High-Density PE): Stiffer, better moisture barrier, harder to seal.
Key Properties:
Low melting point enables easy heat sealing.
Excellent moisture barrier, poor oxygen barrier.
Chemically inert and safe for direct food contact.
Primary Role: The most common sealant film. PE is often the carrier for recycled content (PCR-PE) in sustainable structures.
CPP Key Properties:
Higher temperature resistance than PE (hot fill applications).
Better clarity and stiffness than PE.
Good moisture barrier.
RCPP Key Properties:
Specially formulated to withstand retort sterilization (121°C+ for 30+ mins).
Prevents delamination and maintains seal integrity under extreme conditions.
Primary Role: CPP for general sealant; RCPP is mandatory for the inner layer of retort pouches containing ready-to-eat meals, pet food, etc.
Key Properties:
Excellent adhesion to aluminum foil and other substrates.
Good chemical resistance.
Primary Role: Often used as a tie layer or adhesive layer in foil laminates (e.g., PET/AL/CPE) or as a sealant where strong foil bonding is required. Less common in modern all-plastic structures.
Key Properties:
Exceptional seal-through-contamination (grease, powders).
Excellent hot tack strength (seal strength while still hot), crucial for high-speed VFFS machines.
High clarity and toughness.
Primary Role: Premium sealant for challenging applications like oily snacks, cheese, and liquid packaging.
| Property | PET | BOPP | PA | AL | EVOH | PE | CPP |
|---|---|---|---|---|---|---|---|
| Tensile Strength | Excellent | Good | Excellent | Fair* | Good | Fair | Good |
| Oxygen Barrier | Good | Poor | Good (dry) | Absolute | Excellent (dry) | Poor | Poor |
| Moisture Barrier | Fair | Excellent | Poor | Absolute | Poor (wet) | Excellent | Excellent |
| Clarity | Excellent | Excellent | Good | Opaque | Good | Good | Excellent |
| Heat Resistance | Excellent | Fair | Good | Excellent | Good | Poor | Good |
| Sealability | None | None | None | None | None | Excellent | Excellent |
| Puncture Resist. | Good | Fair | Excellent | Poor* | Fair | Good (LLDPE) | Fair |
*Aluminum foil is fragile and lacks tensile strength on its own; it relies on lamination for durability.
Mono-Material Focus: The push for recyclability favors structures using only PE or only PP families.
Recycled Content: Post-Consumer Recycled (PCR) PE is the most commercially available option for incorporation into sealant layers.
Barrier Dilemma: Traditional high barriers (AL, multi-material EVOH) hinder recycling. Solutions include mono-material PE with EVOH (where EVOH is considered a "minor component") or transparent barrier coatings (AlOx) on recyclable substrates.
Selecting the right combination of films is a balancing act between performance requirements (barrier, strength), processing needs (sealing temperature, machinability), marketing goals (clarity, appearance), and sustainability targets. A high-barrier snack pack might use PET for strength/printability, VMPET for barrier, and LDPE for sealing. A recyclable liquid pouch might use BOPP as the outer, a thin EVOH core, and PE as the sealant layer. Understanding these core materials is the first step in designing effective, efficient, and responsible flexible packaging.
