Laminates for flexible packaging: PET, PE, PP, AL

Look closely at almost any modern pack and what seems to be a single film turns out to be a laminate: several layers of different materials bonded into one web, each doing its own job, from printing and strength to barrier and sealing. Below we break down what goes into a laminate, what PET, PE, PP, PA and aluminum actually do, and how to build the right structure for your product.

What a laminate is and why layers matter

No single polymer can do everything at once: print well, hold its shape, block oxygen and still seal reliably. So manufacturers get clever and bond several materials into one laminate by dry lamination or extrusion. The result is a web with a clear division of labour: the outer layer handles looks and strength, the middle holds the barrier, and the inner takes care of the hermetic seal.

That is why a coffee doypack, a nut pouch and a retort pouch for a ready meal can look alike yet be built completely differently inside. Any well chosen structure always balances three things: product protection, cost and recyclability.

The role of each layer

So you are not lost when a supplier sends over a spec, it helps to know what each of the main materials is for:

• PET (polyester) works on the outside. It gives stiffness, gloss and scratch resistance and offers the best surface for high quality printing, plus it holds temperature and keeps its shape.
• PE (polyethylene) the inner sealant. Under heat it melts and forms a strong hermetic seal. It comes in different densities (LDPE, LLDPE), depending on how strong a seal you need.
• PP (polypropylene) the all-rounder: it can sit outside (BOPP for gloss or matte) or inside (CPP as a sealant), and it adds clarity and stiffness.
• PA (polyamide, nylon) adds mechanical strength and puncture resistance. It is the one you want for products with sharp edges and for vacuum packaging.
• AL (aluminum foil) or metallization the main barrier layer. It fully blocks light, sharply cuts oxygen and moisture ingress and, in turn, extends shelf life.
• Kraft (paper) an outer layer for a natural, eco look; it is always paired with an inner film, otherwise you can forget about a proper seal.

Table of layers and functions

Common laminate combinations

In practice, a handful of time-tested structures cover most orders:

• PET/PE a basic clear or printed structure for dry, undemanding products: snacks, confectionery, frozen goods.
• PET/AL/PE a full aluminum barrier for coffee, spices, dry mixes and anything with a long shelf life that needs protection from light and locked-in aroma.
• PET/MET-PET/PE a metallized version: barrier almost on par with foil, only cheaper and more flexible.
• PA/PE a strong structure for vacuum and products with sharp fragments.
• Kraft/PE or kraft/MET/PE a kraft look on the outside with the barrier tucked inside.

How to choose a structure for your product

Choosing a laminate always starts with one question: what is the product, and what does it need protecting from? A few pointers help from there:

1. Sensitivity to oxygen and light. Coffee, nuts and dry cereals need an aluminum or metallized barrier. Candy, on the other hand, is often fine with a simple structure.
2. Mechanical load. Sharp, heavy or vacuumed products require a PA layer.
3. Heat treatment. Retort pouches need a special RCPP sealant that withstands a 121°C autoclave.
4. Shelf life. The longer a product has to stay on the shelf, the stronger the barrier it needs.
5. Ecology and recycling. If recyclability matters to you, look at a mono-structure based on PE or PP.

At Matrix Pack we work with all of these: PET, PE, PP, PA, aluminum, metallization and kraft, with layer thickness from 25 to 200 microns and a tolerance of plus or minus 5 microns. Minimum order from 5,000 pcs, and we deliver across Ukraine.

Frequently asked questions

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