Nylon Co-Extrusion Vacuum Film: PA/PE Layer Ratio, Puncture Resistance and Seal Strength Data

Overview #

The compliance gap that creates the most costly delays for overseas buyers sourcing nylon co-extrusion vacuum film from China is not material performance — it’s documentation. A PA/PE film that passes puncture resistance and seal strength testing can still be rejected at EU customs or held by an FDA importer of record because the migration testing was conducted under GB/T conditions rather than EU Regulation No. 10/2011 conditions. The test values look similar on paper. The regulatory acceptance is not interchangeable. Before evaluating any Chinese supplier’s compliance package for food-contact vacuum film, the first question to ask is not “do you have a certificate” — it is “under which standard’s test conditions was the migration data generated.”

PA/PE Layer Structure and the Specifications That Actually Determine Compliance #

The functional performance of a nylon co-extrusion vacuum film — and its regulatory classification — is inseparable from the PA/PE layer ratio. Most buyers specify total film thickness (typically 70–120 µm for standard vacuum packaging applications) without specifying the PA layer contribution. That omission creates two problems simultaneously: inconsistent barrier performance across lots, and ambiguity in the food-contact compliance declaration, because the PA layer and PE layer are governed by different positive lists in every major regulatory framework.

In a typical 90 µm PA/PE co-extrusion structure, the PA layer accounts for 25–40% of total thickness (22–36 µm), with the balance in PE. The PA layer provides oxygen barrier and puncture resistance; the PE layer provides the heat-seal surface and moisture barrier. When the PA layer drops below 20 µm in a nominally 90 µm film, puncture resistance measured per ASTM International ASTM F1306 typically falls below 8 N — a threshold that matters for bone-in meat and sharp-edged industrial parts packaging. We have seen Chinese suppliers deliver film where the PA layer had drifted to 18 µm against a specified 25 µm, with no change in total thickness, because the PE layer compensated. The COA showed correct total thickness. The puncture resistance failure only appeared at incoming inspection.

The layer ratio also determines which substances appear in the migration profile. PA layers in Chinese-produced film are predominantly PA6 (polycaprolactam), with caprolactam as the primary specific migration concern. PE layers introduce antioxidants, slip agents, and processing aids — each with separate permitted limits under EU, FDA, and GB/T frameworks.

Most Western buyers do not realize that SAC China Standards GB/T 28118 governs the physical performance testing of food packaging films in China, while the food-contact safety compliance is governed by a separate framework under GB 9685 and GB 4806.6 — and that these two documents are administered by different regulatory bodies. A Chinese supplier can be fully compliant with GB/T 28118 physical testing and still have an incomplete compliance package for export to the EU or US, because the migration testing required by those markets was never conducted.

For buyers sourcing into barrier-films applications where food contact is involved, the layer ratio specification must appear on the purchase order — not just total thickness. This is the single most common specification omission we see in incoming qualification packages.

Regulatory Framework Comparison: EU, US FDA, China GB, and International Standards #

The regulatory landscape for food-contact PA/PE co-extrusion film is genuinely fragmented, and the fragmentation is not cosmetic. Each major market has different test conditions, different substance lists, and different documentation formats. A compliance package built for one market will not automatically satisfy another.

European Union

The primary regulation is EU Regulation No. 10/2011 on plastic materials and articles intended to contact food, with amendments through EU 2020/1245. Under this framework, caprolactam (the primary PA6 migration concern) has a Specific Migration Limit (SML) of 15 mg/kg food simulant. The Overall Migration Limit (OML) is 10 mg/100 cm² or 60 mg/kg food simulant. Migration testing must be conducted using the food simulants specified in Annex III of the regulation, at conditions matching the intended use (e.g., 10 days at 40°C for ambient storage; 2 hours at 100°C for retort applications). A Declaration of Compliance (DoC) is mandatory and must reference the specific regulation, the substances used, and the test conditions. The DoC must be available to competent authorities on request — it is not submitted at import, but it must exist and be traceable.

United States FDA

FDA food-contact compliance for PA/PE film is governed by FDA Guidelines 21 CFR, specifically 21 CFR 177.1500 (nylon resins) and 21 CFR 177.1520 (olefin polymers, covering the PE layer). Unlike the EU positive list system, FDA uses a threshold of regulation approach for low-migration substances, and the compliance determination is the responsibility of the manufacturer or importer. There is no mandatory pre-market approval for most food-contact plastics, but the importer of record bears liability for compliance. For PA6 film, the key extractable limit under 21 CFR 177.1500 is caprolactam extractability: no more than 0.5 mg per square inch of food-contact surface in water at 120°F (49°C) for 2 hours. This is a different test condition from the EU SML test, and the numeric limits are not directly comparable.

China GB Framework

China’s food-contact materials framework is anchored by GB 9685-2016 (Hygienic Standards for Uses of Additives in Food Contact Materials) and GB 4806.6-2016 (Food Safety National Standard — Plastic Materials and Articles for Food Contact). GB 4806.6 sets an OML of 10 mg/dm² and requires that specific migration limits for listed substances be met. Caprolactam is listed with an SML of 15 mg/kg — numerically identical to the EU limit, but tested under GB/T 5009.119 conditions, which differ in simulant selection and contact time from EU Regulation 10/2011 Annex V. The practical consequence: a test report generated under GB/T 5009.119 cannot be directly submitted as evidence of EU compliance, even if the numeric result is below 15 mg/kg.

International Standards

ISO Standards ISO 15105-1 (gas transmission rate testing) and ISO 15106-3 (water vapor transmission rate) are the reference methods for barrier performance characterization. These are method standards, not compliance thresholds — they define how to measure, not what the limit is. Buyers specifying OTR and WVTR on purchase orders should reference these methods explicitly to ensure test comparability across suppliers.

In our supplier qualification program, we require that migration test reports explicitly state the simulant used, the contact time, the temperature, and the regulation under which the test was conducted. Reports that state only “compliant with food contact regulations” without specifying the regulatory framework are rejected as non-conforming documentation — regardless of the numeric results shown.

Seal Strength, Puncture Resistance, and the Test Data Buyers Should Require #

Physical performance data is where Chinese supplier documentation is most inconsistent — not because the film underperforms, but because test methods are not standardized across the supply base. Seal strength reported per ASTM International ASTM F88 (peel test, 180° angle, 25 mm/min crosshead speed) is not the same value as seal strength reported per GB/T 8808. We have received qualification packages from five different Chinese suppliers for the same nominal film specification where seal strength values ranged from 28 N/15mm to 52 N/15mm — not because the films were different, but because three suppliers used ASTM F88 and two used GB/T 8808 with different jaw separation rates.

The test method must be specified on the purchase order. For vacuum packaging applications, the minimum seal strength threshold we recommend is 35 N/15mm per ASTM F88 at the sealing parameters specified for the end-use equipment. Below 35 N/15mm, seal failure rates under vacuum stress increase measurably in distribution testing.

Puncture resistance per ASTM F1306 (slow-rate penetration, 50 mm/min, 8 mm diameter probe) is the most relevant physical test for bone-in meat and industrial parts applications. For a 90 µm PA/PE film with a 25 µm PA layer, a result below 10 N should trigger a layer ratio verification — it almost always indicates PA layer thinning. For a 120 µm film with a 35 µm PA layer, the expected range is 14–18 N. Values outside this range warrant incoming inspection hold.

Most procurement teams over-specify tensile strength (which is easy to achieve and easy to report) and under-specify puncture resistance and seal strength under vacuum conditions. Tensile strength tells you about the film in isolation. Puncture resistance and seal strength tell you about the film in the application. The difference sounds marginal in a specification review. In production, a seal failure rate of 0.3% on a high-volume vacuum packaging line translates to thousands of rejected units per shift.

For buyers also evaluating related sealing consumables and thermal packaging materials, the qualification criteria for seal strength and barrier performance overlap significantly with sealing-thermal category materials — particularly where heat-seal lacquers and co-extrusion structures are used in combination.

Practical Guidance for Buyers #

When sourcing PA/PE co-extrusion vacuum film from China for food-contact applications, the first specification to request from suppliers is not the total film thickness — it is the PA layer thickness and the migration test report with explicit statement of the regulatory framework, simulant, and test conditions. Most buyers ask for a “food contact certificate.” That document, without the underlying migration test data and test conditions, is not actionable for EU or FDA compliance verification.

The sourcing mistake we see most often: accepting a GB/T 5009.119 migration test report as evidence of EU Regulation 10/2011 compliance. The caprolactam SML is numerically the same (15 mg/kg), but the test conditions differ in simulant selection and contact time. An EU customs authority or notified body will not accept a GB/T test report as EU compliance evidence. The consequence is a compliance hold at import — which, for perishable food packaging, means product loss, not just delay.

Before committing to volume order, require three documents: (1) a migration test report explicitly conducted under EU Regulation 10/2011 Annex V conditions (or 21 CFR 177.1500 conditions for US supply), issued by an accredited third-party laboratory; (2) three consecutive production lot COAs showing PA layer thickness, OTR, WVTR, seal strength per ASTM F88, and puncture resistance per ASTM F1306; and (3) a signed Declaration of Compliance referencing the specific regulation, the substances used, and the test laboratory. Suppliers who cannot provide all three within 10 business days of qualification request are not ready for export supply.

Frequently Asked Questions #

Q1: What is the caprolactam specific migration limit for PA/PE vacuum film in the EU, and how is it tested?

A: Under EU Regulation No. 10/2011, the SML for caprolactam is 15 mg/kg food simulant, tested at conditions matching the intended use — typically 10 days at 40°C for ambient storage applications using the appropriate simulant from Annex III.

Q2: Can a Chinese supplier’s GB/T migration test report be used to demonstrate EU food-contact compliance?

A: No. This is where most sourcing decisions go wrong. GB/T 5009.119 and EU Regulation 10/2011 Annex V use different simulants and contact conditions. Even if the numeric result is below 15 mg/kg in both cases, the GB/T report is not accepted as evidence of EU compliance by competent authorities. Require a test report explicitly conducted under EU 10/2011 conditions from an accredited laboratory.

Q3: What seal strength threshold should I specify for vacuum packaging applications?

A: 35 N/15mm per ASTM International ASTM F88 is the minimum we recommend for vacuum packaging. Below that threshold, seal failure rates increase measurably under distribution stress. Always specify the test method on the purchase order — GB/T 8808 results are not directly comparable to ASTM F88 values.

Q4: What compliance documentation should I require from a Chinese supplier before placing a volume order for food-contact PA/PE film?

A: Three documents: a migration test report conducted under the target market’s regulatory conditions (EU 10/2011 or FDA Guidelines 21 CFR 177.1500) from an accredited third-party lab; three consecutive lot COAs showing PA layer thickness, OTR, WVTR, seal strength, and puncture resistance; and a signed Declaration of Compliance referencing the specific regulation and test laboratory. Suppliers who cannot produce all three within 10 business days are not export-ready.

Q5: Is a higher PA/PE ratio always better for puncture resistance?

A: Not automatically. A 40% PA layer in a 90 µm film gives you approximately 36 µm of PA — which improves puncture resistance but increases caprolactam migration potential and raises film cost. For most vacuum packaging applications, a 25–30 µm PA layer in a 90 µm structure delivers the puncture resistance threshold (≥10 N per ASTM F1306) without over-engineering the barrier. Specify what the application requires, not the maximum available.

Published by sinoraw.com Technical Team | Request a sourcing consultation