Polyethylene terephthalate (PET) food-contact compliance is governed by three core instruments: FDA 21 CFR 177.1630, EU 10/2011, and GB 4806.7. PET is a semi-crystalline polyester obtained by direct esterification of terephthalic acid with ethylene glycol or by transesterification of dimethyl terephthalate with ethylene glycol, followed by melt polycondensation and, for container grades, solid-state polymerisation. The polymer is used in water bottles, carbonated soft-drink containers, trays, films, and closures. Because PET processes at high melt temperatures and contains residual monomers, oligomers, catalyst residues, and processing-generated volatiles, food-contact compliance is not a single resin test but a function of polymer composition, conversion conditions, and end-use temperature.

Why Do the Three Regulatory Systems Treat PET Migration Limits Differently?

Under FDA 21 CFR 177.1630, PET is regulated as a polyethylene phthalate polymer. The regulation identifies the condensation monomers and permits the finished article to be used for food contact subject to extractive end-testing. FDA compliance is generally article-specific rather than resin-specific: the same PET resin may be acceptable for one condition of use and not another if extractives exceed the applicable limit. The extractive conditions follow 21 CFR 176.170, which assigns food simulants and time-temperature combinations based on food type, use temperature, and container geometry. There is no single overall migration value for every PET application; rather, the finished article is extracted with water, 3% acetic acid, 50% ethanol, or food oil depending on the intended food and contact conditions.

Under EU 10/2011, PET articles must satisfy an overall migration limit of 10 mg/dm², or 60 mg/kg for infant food. The regulation is structured around a positive list: Annex I Table 1 contains authorised monomers and additives with specific migration limits. Ethylene glycol is assigned 30 mg/kg; terephthalic acid is assigned 7.5 mg/kg. Antimony, typically present because antimony trioxide is used as a polycondensation catalyst, is assigned 0.04 mg/kg expressed as antimony. Food simulants in Annex III are assigned by food type: 10% ethanol for aqueous foods, 3% acetic acid for acidic foods, 20% ethanol for low-alcohol foods, 50% ethanol for alcoholic foods, and vegetable oil for fatty foods. Migration testing follows the EN 1186 and EN 13130 series.

GB 4806.7 also applies an overall migration limit of 10 mg/dm² or 60 mg/kg for infant food. It adds sensory evaluation, potassium permanganate consumption, and heavy metal limits. Specific migration in the Chinese system is controlled through GB 9685 for additives and GB 4806.6 for resin monomers. The test methods are drawn from the GB 31604 series and GB 5009.156. PET resin suppliers and converters must therefore maintain both European and Chinese documentation if the same article is placed on both markets.

The choice of simulant is not a procedural detail. PET is a glassy polymer with a glass transition temperature near 75°C and crystalline melting temperature of approximately 245–260°C for bottle-grade crystallised resin. Aqueous simulants below 60°C do not extensively swell the matrix, but ethanol-containing simulants such as 20% ethanol and 50% ethanol can plasticise the amorphous phase and increase extraction of oligomers. 3% acetic acid can hydrolyse surface ester groups at elevated temperature and mobilise antimony species. Vegetable oil simulants interact mainly through surface partitioning and are limited by the low fatty-food permeability of oriented PET. Discrepancies in migration data between supplier and enforcement laboratories often arise from differences in simulant, contact ratio, or time-temperature condition, not from polymer identity.

Laboratory compliance testing for PET begins with total immersion or cell-based extraction depending on the standard. EN 1186-1 and EN 1186-3 cover overall migration into aqueous and high-cellulose food simulants; EN 13130-1 lists specific migration methods for monomers and additives. The surface-to-volume ratio is critical: EU testing uses 6 dm² of article surface per kilogram of food simulant, while Chinese GB 31604.1 and GB 5009.156 specify similar contact ratios. FDA extractive protocols under 21 CFR 176.170 use a range of contact ratios and solvent volumes. Deviation from the prescribed surface-to-volume ratio produces non-equivalent results because migration is partition-controlled and finite-volume depleted in small bottle formats.

Bottle-Grade PET Retains Low Migration Only within Defined Processing Limits

Commercial bottle-grade PET is supplied with an intrinsic viscosity of 0.78–0.84 dL/g measured by ASTM D4603 in 60/40 phenol/tetrachloroethane at 30°C. This molecular weight range is obtained by solid-state polymerisation at 200–240°C under nitrogen or vacuum. The SSP stage raises the melt-phase polycondensation IV from 0.55–0.65 dL/g and reduces acetaldehyde to below 1 ppm in most commercial lots. Acetaldehyde is not only a sensory concern; it is a volatile migration-relevant compound extractable in water and 10% ethanol simulants.

Conversion conditions can erase some of the SSP benefit. Pre-drying in desiccant dryers with dew point −40°C or lower, polymer temperature 160–180°C, and residence time 4–6 h reduces residual moisture below 50 ppm. In injection moulding of preforms, barrel temperatures above 280°C or screw residence times beyond 8–10 min regenerate acetaldehyde by intramolecular ester pyrolysis and may reduce intrinsic viscosity by hydrolysis. On high-cavitation preform tools such as 48-cavity or 72-cavity hot-runner systems, hot-runner temperature imbalance and screw recovery time affect the residence-time distribution. The observed production failure mode is an increase in headspace acetaldehyde above 5 ppm as measured by ASTM F2013, which can make the preform unsuitable for sensitive water and beverage applications even when the resin originally met its acetaldehyde specification. The migration relevance is direct: acetaldehyde extractables are included in the total organic content detected by overall migration and sensory test programmes.

Higher intrinsic viscosity does not eliminate cyclic oligomer migration. Circulating trimer, mainly cyclic tris(ethylene terephthalate), remains in bottle-grade PET at roughly 1.5–2.5 wt%. The trimer is crystalline and migrates slowly from the glassy polymer below 60°C, but heat treatment can increase surface availability. Process conditions that advance crystallinity can concentrate lower-molar-mass oligomers in amorphous regions or create surface oligomer deposits. Therefore, the same resin lot can produce different total migration results after stretching, heat-setting, and annealing if those operations alter surface composition. Analytical quantification methods for PET migrants include headspace gas chromatography with flame ionisation detection for acetaldehyde, gas chromatography after derivatisation for ethylene glycol, high-performance liquid chromatography for terephthalic acid, and inductively coupled plasma mass spectrometry for antimony. The methods are performance-based but must be validated for each simulant matrix. 3% acetic acid causes matrix interferences for ICP-MS but is necessary for antimony SML determination under EU 10/2011.

When Hot-Fill, Pasteurisation, or Retort Conditions Are Applied to PET Articles

Thermal end use drives test severity. Hot-filled beverages may contact PET at 85–95°C; pasteurised products may reach 95–100°C; retort trays may be processed at 121°C for 30 min. Under EU 10/2011 Annex III, the corresponding migration test conditions are chosen to simulate these exposures. At temperatures above the PET glass transition, chain segmental mobility increases, diffusion coefficients of low-molar-mass migrants rise, and the polymer may undergo additional crystallisation. For antimony, acidic simulants such as 3% acetic acid can produce higher migration than neutral aqueous simulants at the same temperature. For acetaldehyde and ethylene glycol, water and 10% ethanol are effective extraction media. Published data on the exact migration kinetics of all PET oligomers under each specific hot-fill and retort condition is limited; therefore, article-specific migration testing is generally required for new high-temperature applications.

Thermoformed trays and heat-set bottles use oriented or heat-set PET to improve dimensional stability above 80°C. The heat-setting operation at 150–200°C for oriented bottles or 160–220°C for CPET trays increases crystallinity and reduces frozen-in orientation relaxation. However, the high-temperature exposure can also increase the extractable surface oligomer fraction if surface solvent washes are not used. For CPET trays intended for retort use, compliance testing under GB 4806.7 and EU 10/2011 must include the actual retort time-temperature profile. FDA compliance under 21 CFR 177.1630 requires extractive testing under conditions of use; for a retortable tray, this is more severe than ambient water or carbonated beverage testing. Sheet extrusion of PET for thermoformed trays commonly uses a single-screw or twin-screw extruder with L/D ratio of 30:1–40:1 and vacuum venting. A gear pump and screen changer maintain melt homogeneity, but excessive melt temperature or residence time still lowers molecular weight and raises migration-relevant degradation products.

Post-consumer recycled PET is not exempt from the same finished-article requirements. European Commission Regulation 2022/1616 governs recycled plastic materials and requires validation of decontamination efficiency; however, the final article must still comply with EU 10/2011 OML and SML. In the United States, FDA issues letters of no objection for recycling processes that reduce contaminants below threshold of regulation, but the finished PET article still falls under 21 CFR 177.1630. China’s GB 4806.7 evaluates the final material, and recycled PET must meet the same total migration and sensory requirements as virgin PET. This compliance layering means that a recycling process approval is not a substitute for migration testing on the finished article.

Compliance documentation follows three different formats. Under EU 10/2011 Annex IV, the supplier issues a Declaration of Compliance identifying the PET material, manufacturer, date, supported food-contact conditions, overall migration, and specific migration limits. Under GB 4806.7, documentation must demonstrate conformance with GB 4806.6, GB 9685, and the relevant migration test standards. In the United States, FDA 21 CFR 177.1630 places the obligation on the finished-article supplier to verify that the article meets extractive requirements and any applicable food-contact notification; no EU-style Declaration of Compliance is mandated. Batch-to-batch variation in intrinsic viscosity, acetaldehyde content, antimony residue, and cyclic trimer concentration requires process-control limits at conversion and testing intervals. Published data for long-term migration from recycled PET under all three regimes is limited, especially for chemically recycled resin and hot-fill CPET configurations.