What You Need to Know About Antimony Migration in PET and rPET Bottles

Antimony is widely used as a polycondensation catalyst in polyethylene terephthalate (PET) production. Given the global prevalence of PET bottles and packaging, food packaging is a significant dietary exposure pathway for Sb. Studies have confirmed that Sb can migrate from PET into food and beverages, with migration significantly enhanced under high-temperature or acidic conditions. Plastic FCMs are a major source of dietary Sb compared to glass, paper, or metal materials. Evidence also links Sb exposure to cardiovascular and metabolic health risks, highlighting the importance of robust control strategies.

This body of research shifts the focus from simple regulatory compliance toward a more comprehensive question: how can the PET industry effectively control Sb content and migration in the era of rPET and “bottle-to-bottle” recycling to ensure food-grade safety?

I. Raw Material Control: Sb Content as the First Line of Defense

Sb serves as a polycondensation catalyst in PET production, efficiently promoting the esterification and polycondensation of terephthalic acid and ethylene glycol, while supporting desirable product color and performance. Residual Sb in PET resin represents a potential source of migration in food contact applications.

Ensuring the compliance of virgin PET is critical. Wankai New Materials' bottle-grade PET meets FDA, EU FCM, and REACH requirements:

• U.S. FDA: Sb migration ≤ 0.05 mg/L
• EU FCM & REACH: Sb migration limits enforced and potential hazardous substances must be evaluated and controlled

Industry strategies to manage Sb at the raw material stage include:

• Optimizing Sb catalyst levels to control residual content
• Implementing batch-to-batch consistency and internal control metrics
• Promoting low-Sb or Sb-free catalytic systems, such as titanium- or germanium-based catalysts, gradually applied in food-grade PET and high-end rPET

Effective control of Sb at the raw material stage is the foundation for predictable and safe food contact performance. Without this, subsequent process and usage controls can only respond reactively to risk.

II. Application Control: Temperature and Acidic Beverages as Key Factors

Sb migration is influenced not only by raw material content but also by usage conditions. Temperature and acidity are the main drivers of migration, emphasizing the need for proper PET bottle application management.

1. High Temperature Accelerates Migration: Temperature Control is Critical

Experimental data show that Sb diffusion increases with temperature, with migration at 60°C substantially higher than at ambient conditions. Industry best practices include:

Avoid high-temperature filling unless using purpose-designed hot-fill PET (e.g., Wankai WK-811 and WK-811L, suitable for tea, juice, plant-based beverages, and sauces requiring hot-fill or sterilization). These materials comply with China GB 9685/4806.6, EU No. 10/2011, REACH, and U.S. FDA 21 CFR 177.1630, supporting hot-fill up to 90°C while preserving product flavor.

• Control storage and transport temperature: avoid sunlight exposure and high-temperature storage, especially in hot climates.
• High-temperature testing: simulate extreme conditions for products with long shelf life or export to hot regions.
• Compliance alone does not equate to safe use; practical usage scenarios must be considered.

2. Acidic Beverages Increase Migration: Use Low-Risk Materials and Optimized Packaging

Studies using 4% acetic acid as a simulation fluid show Sb migration is most pronounced under acidic conditions. Strategies to mitigate risk include:

• Prioritizing low-Sb PET for acidic beverages to reduce migration potential at the source
• Considering alternative packaging (e.g., glass or high-barrier laminated layers) for high-value or sensitive products
• Reassessing migration risk when extending shelf life or storing under high-temperature conditions
• Optimizing bottle geometry: increased wall thickness or reduced surface-area-to-volume ratio decreases migration rates

By managing temperature and beverage type, PET bottles can retain lightweight and convenience advantages while achieving predictable, controllable, and safe Sb migration.

III. Recycled PET (rPET) Control: Preventing Antimony Accumulation

Chinese research has systematically examined Sb migration in food-grade rPET. The study published in Food and Fermentation Industries—“Study on migration behavior of antimony in food-grade recycled material of polyethylene terephthalate beverage bottle”—experimentally investigated Sb migration in recycled beverage bottle materials.

The research demonstrated that Sb migration increases with temperature and acidity, consistent with international findings. Migration also depends on material structure: thermal history, chain degradation, and crystallinity during recycling affect Sb distribution and diffusion paths. Repeated cycles may amplify migration risk.

To ensure food safety, the industry can implement a three-tier control system:

1. Raw Material Source Control

• Use food-grade recycled PET
• Implement graded recycling to prevent industrial or non-food-grade materials from mixing
• Trace batches and evaluate quality to maintain predictable Sb content

2. Recycling Process Control

• Multiple high-temperature washes and rinses to remove residual contaminants
• Optimize solid-state polycondensation (SSP) to increase molecular weight and reduce migration potential
• Strictly limit or avoid additional Sb catalyst, minimizing secondary migration risk

3. Finished Product Migration Verification

• Conduct migration testing simulating food type, high temperature, and acidic conditions
• Verify migration under long-term storage and transport conditions
• Maintain traceable migration data to support predictable and controllable food safety management
• Relying solely on compliance testing is insufficient; predictable migration behavior is essential for long-term food safety.

IV. From Compliance to Whole-Chain Risk Management

Traditional regulations have primarily focused on antimony (Sb) migration limits, such as 0.05 mg/L. However, scientific evidence demonstrates that high temperatures, acidic beverages, and the use of recycled PET (rPET) can significantly increase Sb migration. Concurrently, research on the potential cardiometabolic health effects of Sb continues to expand. These findings indicate that regulatory oversight is gradually shifting from a purely compliance-based approach toward a long-term safety-oriented perspective. To proactively address these challenges, enterprises should adopt a whole-chain risk management approach, encompassing raw material selection, processing optimization, application control, and recycling practices.

V. Industry Summary and Actionable Guidelines

Effective food-grade PET and rPET management requires integrating raw material, application, and recycling controls to establish a predictable, traceable, and verifiable system for Sb migration risk. This includes ensuring consistent and controlled Sb levels in raw materials, optimizing recycling and polycondensation processes to minimize additional Sb, carefully managing application conditions such as filling temperature and acidic beverage compatibility, and implementing robust food-grade recycling with migration verification for finished products. By applying such an integrated approach, “bottle-to-bottle” PET recycling can simultaneously support sustainability objectives and safeguard long-term consumer health, providing the industry with clear, practical guidance for safe and responsible use.