Flexible Packaging Film Materials Explained: PET, PA, PE, CPP, OPP, AL, Metallized, EVOH & PVDC
A flexible package is rarely made of a single material. It is usually a laminate — several films bonded together, each doing a specific job: one prints well, one seals well, one blocks oxygen and moisture. Understanding these building blocks is the first step to designing packaging that protects your product without overspending.
The Three Basic Jobs
Most films in a laminate fall into one of three roles:
- Outer / print layer: holds the print and gives the pouch stiffness and heat resistance.
- Barrier layer: blocks oxygen, water vapor and light.
- Sealant / inner layer: the layer that melts and bonds to itself during heat sealing.
Common Films and What They Do
PET (Polyester) — the workhorse print layer. It is stiff, transparent, dimensionally stable and withstands heat, which makes it ideal for printing and for the outer layer of retort pouches. It provides moderate moisture barrier but poor oxygen barrier.
PA (Nylon / Polyamide) — tough, puncture-resistant and flexible. Nylon adds mechanical strength and, at low humidity, decent oxygen barrier. It is widely used in vacuum and frozen-food packaging where puncture resistance matters.
PE (Polyethylene) — the most common sealant layer. It heat-seals easily, is flexible and inexpensive, and offers good moisture barrier. Variants such as LDPE, LLDPE and HDPE tune stiffness and seal performance.
CPP (Cast Polypropylene) and OPP (Oriented Polypropylene) — polypropylene films. CPP is a soft, high-heat sealant often used for retort and high-clarity pouches. OPP is a stiff, clear, low-cost outer film with good moisture barrier, popular in snack and confectionery packaging.
AL (Aluminum Foil) — the ultimate barrier. A thin foil layer blocks essentially all oxygen, moisture and light. It is the core of high-barrier laminates for coffee, pharmaceuticals and retort products. The trade-off is cost and that it is not transparent.
Metallized film (VMPET / VMCPP) — a clear film (usually PET or CPP) coated with a thin layer of vaporized aluminum. It gives a metallic look and a large boost in barrier at lower cost and weight than real foil, though not quite as effective.
EVOH (Ethylene Vinyl Alcohol) — an excellent oxygen barrier when dry. Because it loses performance when wet, it is usually buried between two moisture-barrier layers in the laminate.
PVDC (Polyvinylidene Chloride) — a coating or film that blocks both oxygen and moisture well and is less humidity-sensitive than EVOH, though it is more expensive and less common today.
Quick Reference
| Film | Main Role | Strengths |
|---|---|---|
| PET | Print / outer | Stiff, clear, heat-resistant |
| PA (nylon) | Strength | Puncture-resistant, flexible |
| PE | Sealant | Seals well, moisture barrier, low cost |
| CPP | Sealant | High-heat, high clarity |
| OPP | Print / outer | Stiff, clear, moisture barrier, low cost |
| Aluminum foil | Barrier | Blocks O₂, H₂O and light |
| Metallized film | Barrier / look | Metallic finish, improved barrier |
| EVOH | Oxygen barrier | Excellent O₂ barrier when dry |
| PVDC | Barrier | O₂ + H₂O barrier, less humidity-sensitive |
How to Choose
Start from the product, not the film. Ask three questions: What does the product need protection from (oxygen, moisture, light, puncture)? Will it be retorted or frozen? What is the budget? A dry snack might need only OPP/PE, while ground coffee needs PET/AL/PE, and a retort pouch needs PET/AL/CPP or PET/PA/CPP.
If you are unsure where to start, describe your product to the ElagentPak Material Advisor and it will suggest a structure with performance and cost estimates.