Polypropylene (PP) films has become one of the main materials in food packaging because of its excellent mechanical properties, chemical stability and heat resistance. Their non-toxic, odorless, high-temperature-resistant, and grease-resistant characteristics making it widely used in plastic wrap, food packaging bags, bottle cap sealing, etc.. However, with the increasing food safety regulation, polypropylene film safety standards and certification requirements face higher challenges. In this paper, the safety requirements of polypropylene film in food packaging will be systematically analyzed from the aspects of material properties, domestic and foreign standard system, key testing items and certification processes.
Physico-chemical Properties of Polypropylene Films and Their Advantages in Food Contact
Polypropylene is a thermoplastic polymer synthesized from propylene monomers. Molecular stability, high crystallinity ≥ 90%, and homopolymer PP copolymer PP 60-80% confer unique performance advantages:
- Heat resistance: 160-170°C melting point, high temperature resistance above 120°C, suitable for microwave heating and retort pouches.
- Chemical stability: Has good acid, alkali, grease and most organic solvents resistance, minimizes reaction with food ingredients.
- Mechanical performance: high strength, impact resistance, puncture resistance, is ideal choice for automatic packaging lines.
- Transparency and barrier characteristics: through co-extrusion technology, a balance can be struck between high transparency and oxygen/water vapor barrier properties, extending the shelf life of foods.
These properties make polypropylene films ideal for food packaging, but their safety must be ensured through rigorous standards and certification systems.
National and International Standard Systems for Food Contact Materials
(I) China's Standard System
China mainly regulates the safety of food contact materials through the National Food Safety Standards. The main standards for polypropylene films include:
1.GB4806.7-2023 Food exposure to plastics:
- Require polypropylene resins and additives to conform to the list permitted in Appendix A and GB9685-2016.
- Total transport was limited to ≤10 mg/dm2 and specific migrating substances (e.g. primary aromatic amines) were severely restricted.
- Restriction of metal elements (chromium, vanadium, zirconium, hafnium) to 0.01 mg/kg.
2.GB 31604.1-2023 General Rules for food contact material and article Migration Testing:
- Defines the selection and testing conditions (temperature, duration) for simulation media (e.g. water, 3% acetic acid, 10% ethanol, fatty food simulants).
- Testing protocols are required based on food exposure (e.g., short-term contact, long-term storage, high temperature heating).
3.GB/T 10004-2023 Packaging-Plastic Composite Films and Plastic Bags-Dry Layering and Extrusion Layering:
- Specify physical and mechanical properties of polypropylene films (e.g., tensile strength fracture elongation, heat seal strength).
Limit solvent residues to ≤5 mg/m2 to ensure that no hazardous substances remain during production.
(II) International Standard Systems
1.EU Regulation (EU EC) No. 10/2011:
- Limit overall transport to ≤ ≤ 10 mg/dm2 and set specific migration limits (SML) for monomers and additives.
- Sensory testing (odor and taste transfer evaluation) and material-specific restrictions (e.g. prohibition of the use of recycled materials containing bisphenol A) are required.
2.U.S. FDA 21 CFR Part 177.1520:
- Polypropylene is classified into homopolymers (Type I) and copolymers (Type II) and further subdivided into heat resistance (for example, group C when temperatures exceed 120°C).
- chemical extractable testing (e.g. n-hexane reflux extraction after 6 hours with mass ratio ≤ 0.5%) are required to ensure that hazardous substances are not transported.
3.German LFGB (Lebensmittel-und Futtermittelgesetzbuch):
Addition of antioxidant migration limits in the EU framework (e.g. SML of Irganox 1010 = 6 mg/kg).
Sensory tests are needed to confirm that there is no odor or taste transfer in aqueous and olive oil extracts.
Key Test Projects and Technical Requirements
(I) Migration Testing
Migration testing is central to evaluating the safety of polypropylene membranes, including:
Overall migration OML:
Simulate real-world conditions of use (e.g., 40°C/10 days, 100°C/2 hours) to test the total soluble matter in the material.
Test media must be selected according to food type ((e.g., 3% acetic acid for acidic foods, olive oil or isoctane for fatty foods).
Specific Migration Limits:
Individual tests are conducted for suspected harmful substances such as the antioxidants BHT and lubricant calcium stearate.
For example, the EU restricts BHT migration to ≤3 mg/kg, while the U.S. restricts BHT migration. FDA limits calcium stearate concentrations in food food contact layers ≤ ≤1%.
High-Temperature Decomposition Product Testing:
Microwave heating or sterilization may accelerate additive migration or produce new decomposition products.
Trace residue was detected by high sensitivity instruments such as gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry.
(II) Mechanical performance testing
Tensile Strength and fracture elongation:
Ensure that the film remains intact during transport and storage to prevent food contamination.
For example, GB/T10004-2023 requires a longitudinal tensile strength ≥ 20 MPa for composite PP films.
Heat Seal Strength:
Test the peel strength of package seals to prevent leakage due to poor heat sealing.
heat seal strength ≥ 8 N/15mm is normally required.
(III) Sensory Testing
Excerpt Evaluation:
Soak the film in 3% acetic acid or olive oil and assess the color and odor changes of the extract.
Trained ≥ 5 assessors performed blind assays to ensure no odor or sediment.
Instrumental Analysis:
Turbidity meters (accuracy 0.01 NTU) and UV-Vis spectrophotometers (wavelength range 200-800 nm) quantized results.
INTRODUCTION Certification Process and Compliance Strategies
(I) China's Certification Process
Material Compliance:
Ensure PP resins and additives comply with the permitted list in Appendix A. to GB4806.7-2023.
For example, antioxidant BHT usage must ≤ 0.5% and that of lubricant calcium stearate ≤1%.
Type test:
Commissioning CNAS/CMA certified laboratories for comprehensiveproject testing (migration, mechanical performance, sensory assessment).
Test report must include conditions, methods and detailed data.
Application for a production licence:
Submission of the Application for Food Related Products Production Licence, including inspection report process flowcharts flow, to the provincial market regulators.
After on-site examination, obtain SC certification mark.
(II) International Certification Strategies
EU CE Certification:
Complete testing under (EU) No. 10/2011 and label products with "food contact" and glass and fork labels (e.g. alcoholic beverages).
Establish a traceability system to ensure bulk sourcing of raw materials.
U.S. FDA certification:
Submit food a Food Contact Notification (FCN or indirect food additive petitions, including formulation, process and test reports.
Get FDA approval to label the product "Meets FDA Requirements."
German LFGB Certification:
In the EU EU, additional antioxidant transport tests are carried out in accordance with BfR Recommendation XV.
LFGB certification through TÜV or SGS, among others.
Industry Challenges and Future Trends
(I) Challenges
Standard Discrepancies:
Differences in migration limits and testing methods between regions (e.g., 10 mg/dm2 in China and the U.S.). FDA's 60 mg/kg food basis) increases compliance costs.
Emerging risks
Pyrolysis products (e.g., low-molecular-weight oxidized species) may pose a bioactivity risks but are not covered by current standards.
Additive Control:
Low-cost PP products may overuse plasticizers or colorants, requiring stricter control of raw material purity.
(II) Trends
Standard Harmonization:
Major economies are adjusting standards for food exposure materials (e.g. mutual recognition (EU ISO and EU No. 10/2011).
Green Material Innovation:
Nanocomposite PP films containing natural nanoclays reduce the usage of additives while increasing heat resistance.
Supercritical fluid foaming replaces chemical blowing agents to minimize impact on the environment.
Intelligent Testing Technologies:
AI-enhanced high-sensitivity instruments (GC-MS, LC-MS/MS) enable rapid identification and risk assessment of trace residues.
Conclusion:
The safety of polypropylene films in food packaging requires end-to-end control through "feedstock conformity-standard testing-certification audit." Businesses must closely monitor the updating of domestic and international standards (e.g. China GB4806.7-2023, EU (EU) No 10/2011) and establish a database of risk-based material selection. It is essential to optimize the formulation using the Design Quality (QbD) method. In the future, advancements in nanotechnology and green materials will drive polypropylene films in a safer and more sustainable direction, providing stronger food safety safeguard.
