Boosting rPET Quality and Safety in Packaging

The use of recycled polyethylene terephthalate (rPET) is becoming increasingly important in the quest for sustainable packaging. However, recycling virgin PET into rPET presents several challenges that can affect the final product's quality, processability, and safety. This article discusses these issues and explores some of the innovative solutions being developed.

Challenges in rPET Recycling

Degradation of PET
A primary issue is the degradation of rPET during the recycling process. As PET undergoes multiple remelting cycles, it can break down, suffering from thermal degradation, and resulting in a material of lower quality than its virgin counterpart. This degradation can impact the processability, quality, and food safety of packaging made from rPET.

Additive Buildup
Additives play an important role in enhancing PET properties, but they can also present a challenge during the recycling process. They can accumulate over time, leading to potential regulatory and safety concerns. For example, anthranilamide (ATA)-based acetaldehyde (AA) scavengers, commonly used in PET, can deposit on the molds during injection molding. This reduces efficiency and increases cleaning downtime. These scavengers can also lead to the formation of non-intentionally added substances (NIAS) that can accumulate and pose compliance risks.

Solutions for rPET Recycling

To address these challenges, new additive technologies have been developed with recycling in mind. One example is Avient’s patented AA scavenger, ColorMatrix™ AAnchor™ Acetaldehyde Scavenger, developed to mitigate the issues associated with ATA-based solutions. This new technology boasts lower levels of sublimation, does not cause mold deposition, and has a lower risk of exceeding regulatory migration thresholds. Being ATA-free, it also avoids the formation of primary aromatic amines (PAAs), making it safe for use in closed-loop recycling systems.

In addition, the importance of simulating the mechanical recycling process to design new additive technologies cannot be overstated. Standard testing protocols typically involve one full recycle loop, but as the use of rPET increases, it becomes essential to test through multiple recycle loops. Avient has developed a "Heat Stability Protocol" to screen new additive solutions for their impact on color and NIAS through two full recycle loops at 100% recycled content. This provides minimal effect on color shift and product safety.

Importance of Quality and Compliance

As legislation sets new targets for increasing the recycled content in plastic packaging, safeguarding the quality of rPET is critical, especially for food-contact applications. This involves optimizing the recycling process and packaging composition to avoid creating unwanted substances during repetitive processing. A robust development process that simulates the recycling process multiple times is needed to identify and eliminate harmful substances before they enter the rPET stream.

Conclusion

Designing additives and recycling processes with circularity in mind is essential for the future of sustainable plastic packaging. By addressing the gaps that limit recyclability and providing compliance with regulatory standards, the industry can move toward a more sustainable future. The journey is challenging, but with continuous innovation and a commitment to sustainability, a circular economy for plastics is achievable.