Flexible Films & Laminates — Supplier Qualification Guide

COA Field Requirements: What a Credible Flexible Film Supplier Actually Reports #

A Certificate of Analysis for flexible films and laminates should read like a data sheet from an analytical lab, not a marketing checklist. When we receive COAs from new suppliers as part of our qualification process (logged internally as our QM-12 Supplier Incoming Dossier), we screen for a minimum set of measurable fields before we even book the material into our warehouse.

The table below shows the fields we require, the test method we expect the supplier to reference, and the thresholds we use as pass/fail gates for food-contact flexible packaging.

A supplier that cannot populate every row in that table — or substitutes proprietary internal codes for recognised test methods — is a supplier we push back on before approving. COA credibility is not about the number of pages; it’s about traceability back to a specific lot, a specific test date, and a specific instrument calibration record.

For food-contact structures, residual solvent compliance also needs to reference either EU No. 10/2011 on plastic materials in food contact, or FDA 21 CFR §175.300 depending on the destination market. A COA that lists a passing residual solvent figure but cites no regulatory framework is incomplete for export-bound goods.

What Goes Wrong in Laminate Supply — and How to Read the Warning Signs #

Bond strength failures are the failure mode we see most often from under-qualified suppliers, and they rarely announce themselves loudly. What typically happens: a supplier changes their adhesive formulation mid-contract (sometimes due to a raw material substitution, sometimes to cut cost), the cure cycle is shortened on high-volume production days, and the bond strength drops from an acceptable 2.1 N/15mm to 1.1 N/15mm. The film rolls arrive looking identical to the previous lot. Colour is fine. Thickness measures out. The first sign of trouble comes when our operators report delamination at the jaw sealer on the filling line, or worse, when a brand partner reports pouch failures from their distribution partner. We catch this with lot-by-lot T-peel testing on our incoming line — 3 samples per roll, 5 rolls per lot, minimum — which is why our QM-12 protocol requires bond strength be re-measured even when the COA is present. COA figures represent the supplier’s own QC batch sample; they do not represent every roll in the shipment.

OTR and WVTR drift is a subtler problem. Barrier properties in metallised BOPP and AlOx-coated PET can degrade during transit if rolls are stored in high-humidity conditions above 60% RH for extended periods, or if the surface coating is microcracked during rewinding at excessive tension. A COA issued at the time of manufacture may show OTR of 8 cc/m²/day. By the time the rolls reach our warehouse after 6–8 weeks of ocean freight and port storage, the effective barrier can be measurably higher. Our practice for barrier-critical structures is to re-test OTR on arrival using our in-house Mocon Ox-Tran unit rather than relying on the shipped COA. This is not standard across the industry — some converters accept the supplier COA outright — but for any structure going into a product with a claimed 12-month shelf life, we consider the re-test non-negotiable.

COF out-of-spec is the failure mode that brands rarely anticipate during material approval. A kinetic COF above 0.5 on the film surface will cause misfeeds, film bunching, and jaw timing errors on VFFS equipment running at 60+ bags per minute. The COF value is almost never discussed during supplier negotiation — buyers focus on barrier and print quality — but it’s a direct machine-compatibility parameter. When we qualify a new film supplier for a brand running high-speed form-fill-seal lines, COF testing goes into our machine trial protocol before the material is approved for production.

Does FSC Certification Apply to Flexible Films? #

No — FSC certification covers paper and board fibre chains, not plastic film substrates. For flexible films and laminates, the relevant sustainability certification framework is either ISCC PLUS (for recycled or bio-based content claims) or the RecyClass protocol for recyclability assessment in European markets.

This matters for brands targeting EU packaging compliance under the PPWR (Packaging and Packaging Waste Regulation), which is progressively tightening minimum recycled content requirements for plastic packaging from 2030 onwards. If your structure is a mixed-material laminate (PET/AL/PE, for example), no RecyClass rating is currently achievable — that structure will not be certifiable as recyclable under EU guidelines. Brands briefing us on EU-destined flexible packaging increasingly need to make that architecture decision at the brief stage, not after print films are already approved.

Specification Notes for Brand Partners #

When you brief us on a flexible film or laminate project, the minimum information we need to begin a qualification and quotation is: pack format (pouch, roll, lidding), fill product type and weight, target shelf life and storage conditions, filling line type and speed (VFFS, HFFS, manual), and destination market for regulatory purposes.

The most common brief gap we see is missing filling line data. Brands often supply product dimensions and artwork but not the sealer jaw configuration or machine running speed. COF and seal initiation temperature both need to match the filling equipment — a structure that seals beautifully at 140°C may not run cleanly on a line that peaks at 120°C. One iteration of a sample can be avoided entirely if we get the equipment model number upfront.

Our standard sampling timeline for a new laminate structure is 18–22 working days from confirmed specification. Structures requiring barrier re-testing on both sides (OTR + WVTR), or those needing food-contact migration testing under EU No. 10/2011, extend that timeline by 10–15 working days depending on lab scheduling. We run all migration testing through an accredited third-party lab and include the test report in the sample approval package.

Frequently Asked Questions #

How many fields must a COA include before you’ll approve a flexible film supplier?
Our QM-12 protocol requires a minimum of 7 measurable parameters per lot: bond strength, OTR, WVTR, residual solvent (total and individual), haze (for clear films), seal strength, and COF. A COA missing any of these triggers a supplier clarification request before the lot is accepted.

Our current supplier says residual solvent testing isn’t necessary for non-food packaging — is that correct?
It depends on your end use. For non-food consumer goods with no skin contact — outer shipping bags, industrial wrap — the regulatory requirement is lower and your supplier may have a point. For cosmetics, personal care, or any food-adjacent packaging where migration is possible, residual solvent testing against GB/T 10004 or EU No. 10/2011 thresholds is not optional. We’ve seen cosmetic brands caught out by this when their EU retailer requested compliance documentation mid-season.

What’s the minimum bond strength we should be specifying for a retort pouch structure?
Retort structures are a different category from standard dry-goods laminates. For retortable pouches processed at 121°C, we specify post-retort bond strength of ≥ 3.5 N/15mm — significantly higher than the 1.4 N/15mm threshold for ambient structures. The bond degrades under thermal stress, so the pre-retort figure on the COA is not the number that governs performance. Post-process testing is what matters.

Can we switch film suppliers mid-production run without re-qualifying the structure?
We strongly advise against it without a structured change control review. Film substrate changes — even nominally equivalent grades from a different supplier — affect COF, seal window, ink adhesion, and potentially OTR/WVTR. Our internal change control form (CP-03 Substrate Change Notification) requires a minimum of 3 production trial rolls and a seal strength verification before a new substrate is approved as a drop-in replacement.

How do you handle incoming lots where the COA looks fine but the material fails your in-house re-test?
The COA goes on hold and the lot is quarantined in our incoming area. We re-test a second set of samples (5 rolls, 3 specimens each) and issue a non-conformance report to the supplier within 48 hours. If the second test confirms the failure, the lot is rejected and returned. We do not process a lot under deviation approval for barrier or bond strength failures — those parameters are safety-of-supply critical, not cosmetic.

Planning a packaging project? Contact our team to request a complimentary specification review and sample quote.