Recyclability Beyond the Numbers: The Impact of Labels on Plastic Packaging

Recycling can be confusing. Consumers must compare both the resin identification code and format of a package to their municipalities’ list of accepted items to correctly determine what should be placed in the bin.

The municipalities acceptance list is representative of the process employed by the recyclers that receive that material. These lists are generalized to assure a reasonable level of understanding and compliance by the consumer, but there are many factors other than resin identification code and format that determine whether a package truly will be recycled. The APR Design® Guide for Plastics Recyclability is dedicated to addressing these factors and providing guidance to packaging designers. Large sections of the APR Design® Guide are dedicated to labels.

When designing labels for recyclability, there are three primary considerations a designer must make to ensure the intended package will be recyclable and result in a high-quality and yield within the reclamation industry: Coverage, Material Choice and Decorations.

Optical sortation is the most common method of segregating packaging materials into unique material streams and reducing contamination. Optical sortation equipment utilizes near infrared (NIR) or visual scanning to identify a package’s base resin and air jets to divert the package into the appropriate material stream. Additionally, PET and Natural HDPE reclaimers utilize optical sortation to divert colored materials as they will discolor the more valuable natural streams.

High-coverage labels that are greater than 75% of a container’s surface area (55% for containers with a main body volume of 550 ml or less) can interfere with the ability of optical sortation equipment to appropriately sort packaging. To ensure recyclability, designers should choose label materials that either are of similar composition to the material of the package or that allow NIR to traverse and the underlying package to be detected.

PET and Natural HDPE packaging with high-coverage labels also should appropriately sort by color. This can be achieved by limiting label coverage and/or print coverage when the label is clear. Any PET or Natural HDPE packaging label with a surface area greater than the forementioned thresholds should be analyzed for color sortation to mitigate yield loss regardless of print coverage.

It is beneficial to design packaging as close to mono-material as possible to result in the highest quality material when recycled and aid optical sortation in high-coverage uses. Labels of a different material sometimes are a necessity and, when material color is a concern, may have less implications on the reclamation system when appropriately used. Additionally, a significant amount of label material is removed by de-labeling equipment and/or air classification regardless of its construction. Unless a label remains adhered through the entirety of the recycling process, such as with some in-mold applications, the yield benefits of a mono-material construct may be minimal.

When determining appropriate label materials, a designer must consider if the label will be completely liberated and separated from the package during reclamation or if there is a potential to remain with the package/recovery stream. The most common means for label separation is via density.

Packaging typically is cleaned through a process that involves grinding the material into flakes, washing those flakes and then separating out contamination utilizing a float/sink tank. If a label is thermally welded to the package, employs an adhesive that is resistant to the intended wash conditions or is of a similar density (greater or less than a specific gravity of 1.0), some or all of the label will process with the package material. Labels made from incompatible materials that do not fully separate from the material stream will result in yield and quality losses and could render the entire package non-recyclable.

Printed graphics can hinder sortation of PET and Natural HDPE packaging when a high-coverage label is used. Those same inks in any label coverage application may contaminate the material steam and/or process water if not appropriately designed. For PET and Natural HDPE packaging, a designer must choose an ink that is resistant to the wash water conditions as a soluble chemistry may discolor the processed resin and/or effluent wash water. The ink also either should remain adhered to labels of densities opposing that of the packaging material or liberate from labels with similar densities and be of a particle size that can be filtered from the wash water.

In addition to ink chemistries, the use of any metallic materials also should be assessed for potential impact. Metal is a common contaminant because most reclamation systems utilize magnets, eddy current units and/or metal detectors to remove them. A package employing a solid foil label decoration either will be missorted or induce a non-desirable contaminant within the reclamation stream. For this reason, the use of solid metal foils generally will render a package non-recyclable. Transfer products, inks and other non-solid metallic decorations can be considered recyclable if the application has a spherical equivalent of 12 mm or less (16 mm for PET containers).

As an increase has been seen in the adoption of Extended Producer Responsibility legislation and brand commitments to improve the recyclability of their packaging portfolios, the need for plastic packaging to be appropriately designed for recycling never has been greater. The Association of Plastic Recyclers (APR) offers a wide variety of resources to assist packaging designers, including the APR Design® Guide, which can be used to ensure plastic packaging and packaging components are designed for recyclability. APR Design® for Recyclability Recognition also offers recognition for recyclable packaging and a directory of APR-recognized solutions.

Ruben Nance serves as a program director for the Association of Plastic Recyclers (APR) and is responsible for the execution and growth of the Preferred Design Recognition Pathway of the APR’s Design for Recyclability Recognition Program. Nance joined the APR in the spring of 2023, bringing over 14 years of multidisciplinary experience in the plastics and paper packaging and reclamation industries. He lives in Lansing, Michigan, and is a graduate of Michigan State University.  For more information, visit www.plasticscycling.org.