Delamination in Flexible Packaging: Causes and Fixes

What delamination is and what it is not

Delamination is a bond failure between two adjacent layers of a flexible laminate. Those layers may be film, foil, metallized film, paper, adhesive, primer, ink or a coating, and the bond can fail at any interface or within the adhesive itself. Two laminates that look identical from the outside can fail for completely different reasons, so the first job is to name which bond let go.

Useful observations include apparently clean separation, apparent adhesive on both peeled surfaces, film stretching or tearing, ink transfer, separation confined to the heat sealed zone, and changes spreading from a cut edge. These observations can guide investigation, but appearance alone may not distinguish interfacial failure, cohesive failure or substrate damage. Ask the converter or laboratory to identify the failed layer or interface.

A wrinkle, seal channel, cold seal movement or visible bubble does not by itself establish delamination. These defects can coexist with layer separation, so confirm whether a laminate bond has actually failed before selecting corrective actions.

Record the failure before you change anything

A sample from a retained roll, a finished pouch and a returned pack from a customer are three different data points. Capture all three where you can, and write down the conditions each one saw.

Keep the failed sample and photograph it before handling. Peeled surfaces can dry out, oxidise or pick up contamination, so record them as soon as practical.

• Location: flat panel, gusset, corner, seal edge, print area or cut edge.
• Timing: at unwind, after lamination, after printing, after sealing, after filling, or after distribution.
• Pattern: uniform across the web, patchy, in register with the print, or concentrated near edges.
• Peeled surfaces: clean, tacky, split adhesive, ink transfer or fibre tear.
• Environment: fill temperature, product chemistry, humidity, retort or pasteurisation, and time in storage.

Cause families to check in a fixed order

We recommend using the failure history to choose a consistent investigation order and avoid uncontrolled simultaneous changes. Reviewing substrate specifications, treatment records and storage history is one possible starting point. The appropriate checks depend on the structure and available laboratory methods.

Substrate and surface: ask the film supplier whether treatment age, storage conditions or surface additives could affect adhesion in this structure. Review treatment records and roll age alongside the film specification. A treatment reading alone does not establish bond suitability.

Adhesive and coating: compare applicable mix ratio, pot life, coat weight, drying and cure records with the adhesive supplier's instructions. Ask whether insufficient coverage, incomplete cure or retained solvent could explain the observed failure. Solvent retention is relevant only where the process uses solvent; excessive coat weight does not establish a particular failure mechanism.

Ink and coatings: if separation follows the printed pattern, review ink, primer and coating compatibility and applicable drying records with the suppliers. Treat that pattern as an investigation lead, not proof that ink coverage or a coating caused the failure.

Heat history: review applicable lamination settings and subsequent sealing temperature, pressure and dwell against the converter's process specification. Investigate seal contamination separately from interlayer bond failure. Passing an earlier peel test does not establish performance under later sealing or filling conditions.

Mechanical stress: gussets, corner folds, drop impacts and tight pack-outs flex the laminate repeatedly. Delamination that appears only after transit is a reason to review handling stress and the pack-out method early, alongside the other cause families.

Chemical and environmental stress: ask the converter and adhesive supplier to assess compatibility with the actual contents and exposure conditions, including moisture and any thermal processing. Do not infer chemical attack from a product category or surface-energy description alone.

Converting hygiene: slitting dust, blocking on the roll and contamination in the seal zone are easy to overlook and cheap to rule out.

A hypothetical peel test calculation for triage

The numbers below are illustrative only. They are not a quote, a market benchmark or a published specification.

Imagine a hypothetical three ply laminate of 12 micron PET, 9 micron foil and 60 micron PE, with the PET to foil bond under investigation. For this arithmetic example only, three 25 mm wide strips are peeled at 300 mm per minute and the average force over the steady portion of each trace is recorded. This is not a test protocol: the laboratory must define peel geometry, conditioning, cure age, specimen preparation and data reduction before results can be compared.

The average of the three specimens is 4.2 newtons over 25 mm. To express that per 15 mm, multiply by 15 and divide by 25, which gives 2.52 N per 15 mm. This simple width scaling is a reporting convenience that assumes force scales linearly with strip width. Confirm with your laboratory that it matches the method behind your target. Against an illustrative internal target of 3.0 N per 15 mm, the result is 0.48 N per 15 mm short, which is 16 percent below target.

The calculated result is below the hypothetical target under the stated width-scaling assumption. It does not establish that a production bond is unacceptable or explain a failure. Inspect the peeled surfaces and use the laboratory's agreed method, sampling plan and acceptance criteria before drawing conclusions.

The same arithmetic discipline applies to field returns. If 6 pouches out of a 40 pouch sample show edge delamination, that is 15 percent of the sample. Report it as a sample rate, not as a process capability figure.

Decision table: match the pattern to the first check

Use the pattern you recorded to pick one first check rather than running a full audit. The table is a starting point for investigation, not a diagnosis.

Fixes by production stage

Incoming substrate: request applicable treatment records and roll age, and hold stock outside agreed storage limits for quality review. For incoming laminated stock, consider a peel check under an agreed method and cure condition. Unlaminated film requires appropriate incoming checks rather than an interlayer peel test.

Print and lamination: confirm applicable adhesive mix ratio, pot life, coat weight, drying and cure conditions against supplier instructions. If failures track the print, investigate ink and primer compatibility before trialling an approved adjustment. Keep lamination and slitting records by roll so a failure can be traced to a lot.

Slitting and pouching: control dust, check that rolls are not blocking, and verify seal settings against the actual film structure rather than a previous job. Seal area contamination from the fill can contribute, so keep the seal zone clean and check fill temperature.

Pack-out and distribution: review shipper suitability, pouch movement, contact points and drop or vibration history when failures appear only after transit. Consider appropriate cushioning or void fill as a trial variable, and validate the resulting pack-out rather than assuming it prevents flexing.

For simple screening trials, consider changing one variable at a time and retaining a control from the original condition. If interactions are suspected, ask the technical team to design a controlled multivariable trial. Uncontrolled simultaneous changes make attribution difficult.

Practical checklist for the next production run

This checklist is Teal's editorial planning framework for a delamination investigation. It is not a test standard and it does not replace your converter's or laboratory's procedures.

• Retain a roll sample, a finished pouch and at least one field return.
• Photograph peeled surfaces before handling and label each sample with its history.
• Record treatment level and roll age for every lot in the trial.
• Confirm adhesive mix ratio, pot life, coat weight and drying profile in writing.
• Note ink coverage and any overprint varnish on the affected area.
• Log seal temperature, pressure and dwell for the run, and check the seal zone for fill contamination.
• Run a peel check on the trial laminate and keep the raw readings, not just a pass or fail.
• Review pack-out, void fill and drop history if failures appear after distribution.
• Change one variable per trial and keep a control from the original condition.
• Quarantine suspect stock rather than reworking it into another job.

Scope limits and what this guide cannot decide

This guide covers diagnosis of bond failures in flexible laminates. It does not determine whether a package meets a regulatory requirement, and it does not certify any material or structure.

For the regulated special packaging discussed in the CPSC guide, the finished product manufacturer is responsible for selecting suitable packaging and ensuring compliance. CPSC does not approve, certify or endorse specific special packaging, manufacturers or testing firms. Repairing delamination does not by itself demonstrate compliance; reviewers must determine whether further testing or assessment is needed.

If you sell through a channel program, check that program's own packaging requirements in your seller agreement and on its guidelines pages. Requirements change and this guide does not track them.

Carrier packaging guidelines describe cushioning and void fill practices, which affect handling stress, but they do not set bond strength expectations for your laminate.

Finally, arithmetic from peel readings is an estimate for triage. Confirm any corrective action with a structured trial on production stock and with your converter's technical team.

Questions about flexible packaging delamination diagnosis