Polyethylene terephthalate (PET) as a food-contact material is a semi-crystalline polyester derived from purified terephthalic acid and monoethylene glycol. Bottle-grade resin is typically converted at an intrinsic viscosity of 0.80–0.85 dL/g measured according to ASTM D4603-18; sheet-grade material may range from 0.62 dL/g to 0.70 dL/g. The converter’s compliance obligation begins before the first melt, because the phrase PET Declaration of Compliance: What a Converter Must Keep on File identifies a traceable set of supplier declarations, migration test evidence, and production records rather than a single resin certificate. Under Regulation (EU) No 10/2011, the written declaration is governed by Article 15 and Annex IV; under the United States framework, PET resin is controlled by 21 CFR 177.1630 and the general safety provisions of 21 CFR 174.5. Thermomechanical conversion introduces variables not visible in a resin certificate: moisture content, melt residence time, regrind fraction, hot-runner temperature, and additive changes. Each variable can influence the specific migration profile, particularly antimony release from the antimony trioxide polycondensation catalyst, and each variable must therefore be captured in the file if the declaration is to remain valid.

PET Declaration of Compliance: What a Converter Must Keep on File

Article 15 of Regulation (EU) No 10/2011 requires a written declaration for plastic materials and articles at marketing stages other than retail. The declaration content is specified in Annex IV and must include the identity of the business operator issuing the declaration, identity of the material or article, date of declaration, and confirmation that the item complies with the applicable restrictions and specifications. A converter that receives a valid resin declaration does not automatically discharge its own obligation; the converter must issue a further declaration for the finished article when processing, composition, or use conditions differ from those covered by the original declaration.

Article 16 of the same regulation requires appropriate supporting documents to be made available to national competent authorities upon request. For PET conversion, the minimum file comprises resin declarations, migration test reports, GMP documentation, traceability records, and authorization for recycled input where applicable. The table below lists the core record categories and their regulatory anchors.

A common deficiency in converter files is retention of a supplier certificate without conversion-specific test evidence. The supplier declaration covers the resin as supplied; it does not cover additional regrind, antimony catalyst residues after high-temperature processing, or non-intentionally added substances formed during degradation. Article 16 supporting documents should therefore include batch-specific processing logs linking finished article lot identifiers to resin lots.

Which migration limits constrain PET under Annex II of Regulation (EU) No 10/2011?

The EU framework applies an overall migration limit and specific migration limits. For PET, the relevant specific migration limits are those of the monomers and the catalyst metal. Overall migration must not exceed 10 mg/dm² of surface area or 60 mg/kg for food intended for infants and young children, as applicable under the Annex II and Annex V framework. Specific migration of antimony is restricted to 0.04 mg/kg food simulant; this is the most operationally sensitive value for PET because antimony trioxide is used as a polycondensation catalyst.

Migration testing is not a single standard method. Overall migration is determined according to the EN 1186 series using the food simulant and contact conditions assigned under Annex III and Annex V of Regulation (EU) No 10/2011. Specific migration is measured using the EN 13130 series, with simulant selection derived from the intended food type. A PET bottle intended for carbonated soft drinks may be tested in 20% ethanol; a bottle intended for acidic products may require 3% acetic acid. The exact time–temperature condition must be extracted from Annex V, not assumed from a resin certificate.

Antimony migration is influenced by melt residence time and use of regrind. At melt temperatures above 280 °C, prolonged residence in a hot runner can alter the specific migration profile observed in simulant testing, even when the original resin contains antimony below the supplier specification. A converter must therefore retain worst-case migration data for the highest temperature and longest residence time used on the manufacturing line. If a specific configuration lacks published data, testing should be commissioned on finished articles produced under those limits rather than relying on generic PET data.

In a high-cavity PET preform molding cell, the compliance file and the process control system overlap. Drying is the first control point: PET granules exposed to ambient relative humidity above 60% absorb moisture rapidly, and melt-phase hydrolysis can reduce intrinsic viscosity by 0.05 dL/g or more when moisture exceeds 0.02 wt%. Desiccant-wheel dryers are typically set to 160–180 °C with a dew point of −40 °C for 4–6 h to bring residual moisture below 0.005 wt%. The dryer parameters, hopper residence time, and dew-point trend data are GMP records under Regulation (EC) No 2023/2006.

The injection molding barrel and hot runner introduce a second control boundary. Melt temperature is held at 270–290 °C, and mold temperature for amorphous preforms is typically 8–12 °C. Residence time in a hot runner for a 96-cavity preform mold can exceed 5 min when production is interrupted; the recorded barrel temperature, hot-runner zone temperature, and hold time must be traceable to the finished lot. These records convert a supplier declaration into a verified processing window. Acetaldehyde formation increases as melt temperature approaches 290 °C; acetaldehyde is not an SML constraint under EU 10/2011, but it is a sensory specification for bottled water and must be retained as a quality record.

Extrusion of PET sheet adds further record types. Single-screw extruders with 30:1 to 36:1 L/D and vacuum venting maintain melt temperature near 260–280 °C; chill roll temperatures of 20–40 °C control crystallinity and thickness. Batch records should include raw resin lot, regrind percentage, vacuum level, die temperature, and final sheet intrinsic viscosity. Sheet producers must retain the same EU declaration chain as preform molders because downstream thermoformers use the sheet as an intermediate food-contact article.

When regrind, recycled resin, or process aids enter the PET stream

A converter that introduces post-industrial regrind changes the plastic composition relative to the original resin declaration. Under Regulation (EU) No 10/2011, regrind is not automatically non-compliant, but the finished article must still meet the same overall and specific migration limits. The file must include a validated regrind ratio, drying history, and test evidence for the worst-case regrind fraction. The same applies to introduction of recycled PET under Regulation (EU) 2022/1616; recycled PET must be obtained from a suitable decontamination process and must be traceable to an authorized recycling installation.

Process aids, colorants, oxygen scavengers, and acetaldehyde control additives must be covered by their own declarations under EU or national food-contact provisions. A converter using an amine-based processing aid in PET may induce aminolytic chain cleavage; such use should be excluded from the compliance file unless explicitly tested for molar mass retention and migration of reaction products. Silicone or lubricant spray used on molding equipment must not contaminate the food-contact surface and must be recorded as a plant hygiene control under Regulation (EC) No 2023/2006.

Non-intentionally added substances from thermal degradation, including acetaldehyde, cyclic oligomers, and potential degradation fragments, require risk assessment under the general Union list framework. The converter file should retain any gas chromatography–mass spectrometry screening of PET articles when the process uses high regrind, long residence time, or melt temperatures above 280 °C. Published data for highly specific configurations is limited; therefore, chromatographic screening with validated detection limits is often used to support the risk assessment.

Competent authorities may inspect the converter file under Article 16 of Regulation (EU) No 10/2011 without prior announcement. The file must connect each finished article lot to the resin declaration, processing log, and migration test report. A standard audit sequence follows the lot number from the pallet label to the daily dryer log, hot-runner temperature record, regrind ratio, and laboratory test report. Missing links between these documents are a frequent cause of nonconformity, even when the resin itself is compliant. For that reason, the operative requirement is not merely possession of the declaration but the existence of a traceable evidentiary chain.

This traceability requirement extends to distribution. Article 15 obligations apply to the marketer; a converter selling an intermediate PET sheet or preform must issue its own declaration for that intermediate. The downstream customer cannot be assumed to possess the original resin supplier declaration. The file should therefore include a copy of the downstream declaration issued by the converter and a reconciliation table that maps customer shipment numbers to the internal lot numbers used in testing.