What Do We Know About RPET in Food Packaging?

2024-10-06

The application of recycled polyethylene terephthalate (rPET) to food contact is mainly faced with food safety challenges. Zeng Yan, Zhang Dijun and others from Jinan University reviewed the regulations of recycled PET (rPET) for food contact and the typical unintentional additives (NIAS) in rPET, with the title "Risk of non-intentional Additives in food-grade recycled polyethylene terephthalate", in order to provide reference for the establishment of regulations and standards for rPET for food contact in China.

In May 2020, the "Application Process for Suitability of PET reprocessed ester Granule Raw Materials for Packaging Manufacturing of Food Containers" promulgated by Taiwan, China, took the lead in using rPET for food contact materials in China. Taiwan has referred to the safety assessment and supervision management model of the European Union and the United States, taking challenging experiments as the process safety assessment method, and using the food and drug administration agency as the review body.

So far, Chinese mainland's attitude towards recycled plastics for food contact has gone through three stages.

The prohibition phase

The former Ministry of Health in 1990 promulgated the "Food plastic products and raw materials hygiene management Measures", the former State General Administration of Quality Supervision, Inspection and Quarantine promulgated in 2006 "Food plastic packaging, containers, tools and other products production license review rules" clearly stipulate that Food Packaging materials shall not use recycled plastics.

Case permit phase

In 2008, Beijing Yingchuang Company through the introduction of foreign advanced technology and equipment production of rPET bottles was approved by the former Ministry of Health and the former Quality Inspection Bureau, becoming the country's legal use of rPET, and use it for food contact products of the first enterprise.

No clearly defined phases

In the new rules for the Implementation of the Production License for Food Related Products such as plastic packaging Containers promulgated by the State Administration for Market Supervision and Administration in December 2018, the previous provisions that were not allowed to be used were removed, and the content on the use of recycled plastics for food contact was not involved.

The safety assessment of NIAS in rPET for food contact rPET is inevitably exposed to food during the process of food contact, and its components will migrate to food, thereby affecting food safety. The key to evaluating the safety of food-contact rPET is to accurately determine the substances and their content that migrate from the food-contact material to the food.

The safety hazards of rPET come from two aspects. On the one hand, they come from the migration of chemical substances that have been approved for use in the material, including monomers, initiators, and additives, to food in excess; on the other hand, they come from the pollution of food caused by NIAS migration, and NIAS-induced pollution is becoming the main source of food-contact material safety hazards.

01
Volatile Organic Compounds (VOCs) in rPET are mostly the result of thermal oxidation and thermal degradation of polymers during recycling, a mixture of reaction products and degradation products of several compounds.
In the combination of high temperature, extreme shear stress, and oxygen, rPET materials form organic free radical molecules, and then these free radical molecules react with each other to produce oxidized compounds. It is particularly noteworthy that post-consumer PET contains more pollutants, such as dyes, various additives, and heavy metal substances, which exist during the recycling process. The presence of these substances may accelerate the production of VOCs.
Frequently present VOCs in rPET, such as formaldehyde, benzene, and styrene, not only have unpleasant special odors but also often come with stimulating, toxic, carcinogenic, and teratogenic adverse effects. If excessive VOCs in rPET migrate to food, it will cause great harm to public health and the environment.

02
Non-volatile organic compounds (NVOCs) oligomers are well-known polymer side products in PET and rPET, and are also the main non-volatile organic compounds. In order to ensure the safety of rPET during use, the migration of oligomers must be evaluated. Oligomers are polymers formed by a few monomers, which can form during the manufacturing process of polymers, and may also decompose to form during use.

Due to the complexity of oligomers, identifying and conducting migration studies on food simulants in rPET are challenging. EU No.10/2011 and GB 9685—2016 do not have migration limits for PET oligomers, but it cannot be denied that excessive migration of oligomers may have an impact on the quality and safety of food and human health.

03
Heavy metals

The quality level of rPET bottles made by different manufacturers may vary, even if they are made from the same recycled material. rPET plastic bottles made from the same recycled material can also have different levels of heavy metal migration. Post-consumer PET recycling is obtained by collecting homogeneous deposits (such as carbonated and non-carbonated beverage bottles) or from heterogeneous deposits contaminated by PVC, nylon, and various additives, so rPET may be contaminated by various materials.

The sources of heavy metal contaminants mainly exist in the following aspects: the first is the heavy metal pigments contained in the original PET plastic, the second is the metal impurities in the recycling process, and the third is the metal catalyst used.

According to many research results at home and abroad, many NIAS migration and residues in rPET are small, and rPET has the potential to become a food contact material. Therefore, under the background of the vigorous development of rPET for food contact, the country should clarify the legal status of rPET and formulate relevant rPET safety standards as soon as possible under the existing recycling system, so as to ensure the safety of rPET for food contact and a large number of international applications.