Laminated Packaging: How Lamination Works and Why It Matters

A poorly bonded laminate can separate during converting or use. Laminated film is a packaging material made by bonding two or more separate webs, such as plastic films, aluminum foil or paper, into one structure that runs and converts as a single web. Lamination in packaging is the step that does the bonding. Each web does a different job: the outer layer carries print, a middle layer blocks oxygen or moisture, and the inner layer seals. Lamination is the main way to combine materials that cannot be coextruded together, which is why most printed pouches and high-barrier packs are laminates.

This page covers how lamination works and what can go wrong. For the three film builds side by side, see flexible packaging film. “Laminated flexible packaging” usually means these multi-web structures.

Before choosing a process, confirm:

• Whether the adhesive carrier is dried before or after the webs meet.
• Whether a reactive adhesive needs a controlled cure before conversion or release.
• Whether the complete laminate is qualified for the product and heat exposure.

How lamination works

Lamination joins webs in a nip between rollers, with something in the middle that bonds them. The bond is either a thin layer of adhesive or a layer of molten polymer. The result is a single web that is wound, cured if needed and slit, then used as rollstock or converted to pouches. The same word also covers dry bonding, extrusion bonding and, in some cases, thermal bonding, though the first two dominate packaging.

Illustrative layer order, outside to inside; optional layers and actual thicknesses follow the approved specification:

Adhesive lamination

Adhesive lamination coats one web and bonds it to another. The position of the dryer distinguishes dry from wet bonding; solventless systems have no carrier to evaporate. A manufacturer’s public process guide describes the dry and wet sequences, and an adhesive manufacturer’s guide describes solventless coating and nipping.

Adhesive systems give a thin bond line, which is why adhesive is often left off a structure notation. Adhesive amount is specified as a coating weight in g/m² on the adhesive maker’s data sheet; the dry bond-line thickness in µm follows from that weight and the adhesive’s solids and density, so take both figures from the data sheet for the grade and process you use rather than from a general rule. Many systems are two-part and reactive, so the adhesive keeps cross-linking after lamination and the bond keeps developing.

Extrusion lamination

In extrusion lamination, a molten polymer, most often PE, is extruded as a curtain between two webs and cooled in the nip. The polymer acts as both the bond and an added layer. It gives a thicker bond line than adhesive lamination and can also work as a sealant or a barrier. A related process, extrusion coating, puts the polymer on one web only. Primer and surface treatment requirements depend on the substrate, resin and existing treatment. Confirm the selected route in the process specification; primer is not a fixed requirement for every extrusion laminate.

Curing time

Reactive adhesives continue developing their bond after lamination. Use the technical data sheet for the exact adhesive/hardener pair and approved substrates to define time and temperature for slitting, pouch making and final release. Record the document revision, lamination time and actual storage conditions on the batch; a calendar hold alone does not demonstrate readiness.

Slitting, pouch making or filling before cure is complete can cause problems:

• Low bond strength: the layers can separate when the pouch is sealed, flexed or filled.
• Tunneling: the layers pull apart in a ridge when the web is wound tightly.
• Variable seal behavior: a bond that is still developing may behave differently in the heat of the seal bar.
• Residual migration: unreacted components can move into the pack. Food-contact rules vary by destination market, so ask your supplier for documentation and confirm the requirements you must meet.

Takeaway: Release the batch only against its agreed cure, bond and applicable food-contact acceptance records. Do not copy a hold time from a different adhesive grade.

Bond strength and delamination

Bond strength is the force needed to peel the layers apart, measured in a peel test. It differs from seal strength, which measures the heat seal (ASTM F88 is the common seal strength method). Peel results depend on the test speed, the angle and the sample, so compare values only from the same method.

Common causes of delamination:

1. Insufficient cure: the adhesive has not reached full bond.
2. Poor surface treatment: low surface energy on a film prevents wetting by the adhesive or ink.
3. Wrong coat weight: too little adhesive leaves dry spots; too much can cause slip or tunneling.
4. Contamination: slip additives, ink residues or moisture at the interface.
5. Heat and product attack: hot fill, retort or aggressive products (oils, acids, alcohol, surfactants) can weaken some adhesives. Retort needs adhesives rated for it; see retort pouches.
6. Ink that is not compatible with the adhesive: the bond fails at the ink layer.

Ask what the adhesive is rated for, and test the actual product with the actual structure.

Reverse-printed laminates

Reverse printing puts ink on the inside face of the transparent outer web, which then gets laminated. The ink is trapped between layers, so it does not scuff and the surface is glossy. The print also becomes part of the bond: the ink must be compatible with the adhesive, and the adhesive coats over ink instead of film, so ink coverage and any white backing layer affect bond strength. Thin ink films with good wetting generally bond better than heavy flooded areas.

Common laminate structures

The examples below use the standard outside-to-inside notation. They are illustrations, not specifications, and thicknesses vary.

Retort suitability cannot be inferred from a generic PE sealant notation. Obtain the specific sealant and adhesive grades, the intended heat cycle and finished-pouch validation; see retort-pouch material qualification.

See metallized film and aluminum foil for the barrier layers, and high barrier film for options without foil.

Laminates vs coextrusion

Laminate when you need premium print or high barrier. Use coextrusion when one pass and a single polymer family are enough.

Recycling laminates

Laminates of dissimilar materials are the hard case for recycling because collection and sorting systems struggle to separate PET, PE, nylon and foil. Adhesive and ink add a further complication. The practical responses are all-PE or all-PP laminates, where the layers are one polymer family, and thin barrier coatings that preserve recyclability. See mono-material packaging and recyclable flexible packaging. Recyclability depends on local collection and on guidelines from bodies such as APR and RecyClass, so confirm the rules for each market.

What to put in a laminate specification

Use this record with the approved structure, rather than a generic laminate recipe.

Lamination is one stage in how flexible packaging is made.

Questions about laminated film packaging

What are the three types of lamination?

In packaging they are usually listed as dry, wet and extrusion lamination. Dry lamination joins webs after the adhesive carrier has been dried off, wet lamination joins them while the adhesive is still wet and needs a porous web such as paper, and extrusion lamination uses a molten polymer as the bond. The process table also separates solventless bonding, which needs no carrier-drying step.

What to use instead of lamination?

Consider a single-layer or coextruded film when its material combination can meet the pack’s protection and sealing requirements. Paper may still need a coating or laminate. Compare film builds and paper-based packaging limits before replacing the laminate.

Sources and method

• A manufacturer’s dry and wet process guide places drying before bonding for dry lamination and after bonding for wet lamination.
• A manufacturer’s wet-lamination substrate guide lists paper-based combinations.
• An adhesive manufacturer’s solventless process guide describes coating, nipping and reactive bonding.
• TAPPI extrusion-coating and laminating material explains the molten-polymer/chill-nip sequence; a manufacturer’s line overview lists treatment options.

Public process references checked 9 October 2026. They explain process routes, not approval of a particular package. Cure schedules and acceptance limits come from the actual grade documents and qualified batch process.