Determination of Migration Levels in Plastic Films: Standards, Methods, and Applications

Plastic film migration testing quantifies the transfer of substances such as residual monomers, plasticizers, antioxidants, and heavy metals from plastic films into food or food simulants under foreseeable conditions of use. This article provides a professional overview of overall (global) and specific migration determination for plastic films, covering applicable standards such as GB 4806.7, GB 31604, EN 1186, EN 13130, and EU Regulation No 10/2011, together with food simulants, test conditions, analytical techniques, and typical regulatory applications for food-contact packaging materials.

Technical Overview

Migration is the transfer of substances from a plastic film into a contacted medium—most commonly food, food simulants, or pharmaceutical products—under the worst foreseeable conditions of use. Migrating substances may include residual monomers, oligomers, plasticizers, antioxidants, slip agents, processing aids, colorants, adhesive components, printing ink constituents, and their degradation products. Because plastic films are among the most widely used direct food-contact materials, regulatory authorities worldwide have established strict migration limits and harmonized test methods to ensure consumer safety.

Migration testing is divided into two complementary categories. Overall migration (also called global or total migration) measures the total mass of all non-volatile substances released from the film, typically expressed in mg/dm² of contact area or mg/kg of food. Specific migration measures the release of individually regulated substances, each of which carries its own specific migration limit (SML). The principal regulatory frameworks include the Chinese national food safety standards GB 4806.6 and GB 4806.7, the Chinese method standards GB 31604 series together with GB 5009.156 for pretreatment, the European Union Regulation (EU) No 10/2011 as amended, the US FDA regulations under 21 CFR Parts 175–178, and the harmonized European test standards of the EN 1186 and EN 13130 series.

Under most regimes, the overall migration limit (OML) for plastics intended for food contact is 10 mg/dm² of contact surface, or 60 mg/kg where the result is expressed per kilogram of food for filled articles. Specific migration limits vary widely, from values as low as 0.010 mg/kg for highly restricted groups such as primary aromatic amines up to 60 mg/kg for less restricted substances.

Testing Samples

Polyolefin Films (LDPE, LLDPE, HDPE, CPP, OPP)

Polyethylene and polypropylene films are the most common flexible packaging materials, used for bags, liners, wraps, and pouches. Typical migration concerns include slip agents (such as fatty acid amides), phenolic and phosphite antioxidants, antistatic agents, and, in recycled-content materials, potential legacy contaminants.

Polyester (PET) and Polyamide (PA) Films

Biaxially oriented PET films and nylon films are used in barrier laminates and retort pouches. Relevant migratable species include cyclic oligomers, antimony catalyst residues for PET, and residual caprolactam for polyamide 6 films.

PVC Cling Films and Plasticized Films

Flexible PVC films used as cling wrap for food require close monitoring of plasticizers (such as phthalates and adipates), residual vinyl chloride monomer, and stabilizer components, because these additives are comparatively mobile in the polymer matrix.

Multilayer Laminated and Composite Films

Laminates combining PE, PP, PET, PA, aluminum, EVOH, or PVDC layers may introduce additional migration sources from polyurethane lamination adhesives—most notably primary aromatic amines derived from isocyanate monomers—and from printing inks via set-off and penetration.

Biodegradable and Specialty Films

PLA, PBAT, PHA, and other biodegradable films, as well as pharmaceutical blister and lidding films, are tested for residual monomers such as lactide, oligomers, and functional additives to demonstrate compliance with the applicable food-contact or pharmaceutical packaging requirements.

Testing Items

Depending on the film type, intended use, and target market, a typical migration testing program covers the following items:

• Overall migration (global migration) into aqueous, acidic, alcoholic, and fatty food simulants
• Specific migration of regulated heavy metals and elements (e.g., barium, cobalt, copper, iron, lithium, manganese, zinc, lead, cadmium, chromium, arsenic, antimony)
• Specific migration of phthalate plasticizers (e.g., DEHP, DBP, DINP, DIDP, BBP)
• Specific migration of bisphenol A and other bisphenols
• Specific migration of primary aromatic amines from polyurethane adhesives
• Specific migration of residual monomers, including vinyl chloride, vinylidene chloride, styrene, acrylonitrile, and caprolactam
• Specific migration of antioxidants and light stabilizers (e.g., BHT, BHA, hindered phenols, benzophenone-type UV absorbers)
• Formaldehyde and other carbonyl compounds
• Potassium permanganate consumption in aqueous extract
• Decolorization test for dyed and printed films

Testing Methods

Sample Preparation and Contact Geometry

Film specimens are cut into strips of known surface area, handled with clean gloves and contaminant-free tools, and exposed to the selected food simulant by total immersion, one-sided cell exposure, or pouch formation, depending on the intended end use. Only the surface intended for food contact is exposed in cell and pouch methods, whereas total immersion exposes both sides. Unless the actual packaging geometry is reproduced, a default surface-area-to-food-volume ratio of 6 dm² per kilogram of food is commonly applied, allowing results to be expressed in mg/dm².

Selection of Food Simulants

Food simulants are assigned according to the food category. Under EU Regulation No 10/2011, the simulants are 10% ethanol (aqueous foods), 3% acetic acid (acidic foods), 20% and 50% ethanol (alcoholic foods), vegetable oil for fatty foods with 95% ethanol or iso-octane as substitute simulants, and a modified polyphenylene oxide porous polymer for dry foods. The Chinese GB 31604 framework uses water, 4% acetic acid, 20% and 50% ethanol, and n-hexane as the fatty food simulant. US FDA protocols employ aqueous ethanol solutions and n-heptane under specified extraction regimes.

Migration Test Conditions

Time and temperature conditions are selected to represent the worst foreseeable use of the film. Typical regimes include 10 days at 40°C for long-term ambient storage, 2 hours at 70°C for hot-filling followed by ambient storage, 2 hours at 100°C for contact with boiling foods, and 2 hours at 175°C for high-temperature oven or microwave applications. Elevated-temperature sterilization applications may require retort conditions above 100°C. Frozen and refrigerated storage is generally tested at 10 days at 20°C, because migration is kinetically limited at sub-ambient temperatures.

Determination of Overall Migration

After exposure, the film is removed and the simulant is transferred to a preconditioned evaporating dish, evaporated to dryness, dried to constant mass at approximately 105°C, and weighed. The residue mass, corrected by a blank determination, is divided by the exposed surface area to yield the overall migration result in mg/dm², which is compared against the 10 mg/dm² limit. Fatty simulants require additional extraction and weighing steps to distinguish migrated oil film from true migratable residue. The EN 1186 series defines the immersion, cell, and pouch methods for the EU, while GB 31604.8 and related standards define the corresponding Chinese procedures. Because gravimetry does not capture highly volatile substances, specific migration testing remains necessary for such species.

Determination of Specific Migration

Specific migration is determined by instrumental analysis of the migration solution. Phthalates, monomers such as styrene and caprolactam, and other semivolatile organics are quantified by GC-MS or GC-FID; vinyl chloride and other volatile monomers are determined by headspace GC; bisphenols, primary aromatic amines, and antioxidants are determined by HPLC with UV, fluorescence, or MS/MS detection; and elements are determined by ICP-OES or ICP-MS after appropriate digestion of the simulant. Where the simulant is oil or an organic solvent, extractive clean-up or solvent exchange is performed before analysis. Validated methods must achieve limits of quantification at or below the applicable SML to support a conformity decision.

Method Validation and Quality Control

Accredited third-party laboratories support migration results through blank controls, duplicate determinations, matrix-matched calibration, recovery studies, and participation in interlaboratory proficiency testing. Test reports document the film identification, simulant, exposure geometry, time–temperature condition, measured values, uncertainty, and the pass/fail conclusion against the cited regulatory limits.

Applications

Migration determination for plastic films serves multiple regulatory and commercial purposes across the packaging value chain:

• Regulatory compliance demonstrations for food-contact materials placed on the Chinese, EU, US, Japanese, and other national markets
• Export conformity support for converters and brand owners facing destination-market requirements
• New material and formulation development, including additive selection and dosage optimization
• Supplier qualification and incoming quality control of purchased films and laminates
• Process change and ink or adhesive changeover evaluations for existing packaging structures
• Support for food-contact notifications and dossiers submitted to regulatory authorities
• Verification of structures containing recycled content, where challenge testing and contaminant screening are required
• Root-cause investigation of sensory defects, off-odors, or contamination incidents linked to packaging

For pharmaceutical and medical packaging films, analogous migration studies support compatibility and safety assessments under the relevant pharmacopoeial and packaging regulations. In agricultural contexts, similar migration methodology is applied in research on additive transfer from mulch films to soil and crops.

FAQ

What is the difference between overall migration and specific migration?

Overall migration measures the total quantity of all non-volatile substances released into a food simulant and is compared against a single limit, normally 10 mg/dm². Specific migration quantifies individual regulated substances, such as a particular plasticizer or monomer, each of which has its own migration limit that may be far lower than the overall limit. A film can pass overall migration testing yet fail specific migration testing, so both determinations are required.

How are food simulants selected?

Simulants are assigned according to the character of the food the film will contact: water or dilute ethanol for aqueous foods, dilute acetic acid for acidic foods, aqueous ethanol of appropriate concentration for alcoholic foods, and vegetable oil, iso-octane, n-hexane, or 95% ethanol for fatty foods, depending on the applicable regulatory regime.

Why is testing performed at 40°C for ten days for room-temperature storage?

Regulatory frameworks apply accelerated time–temperature conditions that have been scientifically demonstrated to overestimate migration relative to long-term ambient storage. Ten days at 40°C is the conventional worst-case surrogate for extended room-temperature contact in both the EU and Chinese systems.

How is the contact area handled when the real package geometry is unknown?

When the actual surface-area-to-volume ratio cannot be established, a conventional ratio of 6 dm² of contact surface per kilogram of food is assumed, and results are expressed in mg/dm². Where the true package geometry is known, the actual ratio is used, and results may be expressed in mg/kg.

Which standards govern plastic film migration testing?

The principal references are GB 4806.7, GB 31604 series, and GB 5009.156 for China; Regulation (EU) No 10/2011 with the EN 1186 series for overall migration and the EN 13130 series for specific migration in Europe; and the FDA protocols under 21 CFR Parts 175–178 for the United States, supplemented by ISO and JIS methods where applicable.

How long does migration testing take?

The exposure phase itself may last from two hours to ten days depending on the selected condition, with additional time required for evaporation, drying, instrumental analysis, and report issuance. A complete overall and specific migration program for a multilayer film is typically completed within two to four weeks by accredited third-party laboratories, depending on the number of simulants, conditions, and target analytes.