Enabling the Polymer Circular Economy: Innovations in Photoluminescent Labeling of Plastic Waste for Enhanced Sorting

Abstract

It is widely accepted that moving from a linear to circular economy for plastics will be beneficial to reduce plastic pollution in our environment and to prevent loss of material value. However, challenges within the sorting of plastic waste often lead to contaminated waste streams that can devalue recyclates and hinder reprocessing. Therefore, the improvement of the sorting of plastic waste can lead to dramatic improvements in recyclate quality and enable circularity for plastics. Here, we discuss current sorting methods for plastic waste and review labeling techniques to enable enhanced sorting of plastic recyclates. Photoluminescent-based labeling is discussed in detail, including UV–vis organic and inorganic photoluminescent markers, infrared up-conversion, and X-ray fluorescent markers. Methods of incorporating labels within packaging, such as extrusion, surface coatings, and incorporation within external labels are also discussed. Additionally, we highlight some practical models for implementing some of the sorting techniques and provide an outlook for this growing field of research.

Trends in Polyester Upcycling for Diversifying a Problematic Waste Stream

“…40,50,94,139 Ingenuity in labeling of bottles, for example, can lead to improved sorting capabilities and therefore increase the rate at which this large postconsumer source is collected and effectively reutilized. 140 There also deserves to be significant development in terms of reutilizing particular sources of postconsumer polyesters. Beverage bottles represent an idealized source of polyester, owing to the relatively pure nature and widespread availability of postconsumer bottles.…”

“…Effectively applied, it seems self-evident that recycling more [polyester] plastic waste will minimize the use of virgin raw materials and simultaneously reduce plastic pollution. Not only does this require better collection and sorting, but technological breakthroughs in terms of catalytic efficiency in recycling/upcycling are critically important. ,,, Ingenuity in labeling of bottles, for example, can lead to improved sorting capabilities and therefore increase the rate at which this large postconsumer source is collected and effectively reutilized …”

Polymer up-cycling by mangana-electrocatalytic C(sp3)–H azidation without directing groups

“…Thus, the up-cycled polymers could reenter the in-use cycle as an additives to facilitate polymer sorting in a tracer-based sorting approach. 62 …”

Review and Assessment of Existing and Future Techniques for Traceability with Particular Focus on Applicability to ABS Plastics

“…This is because some chemical compounds can undergo a so-called photoluminescent up-conversion. This is accomplished by a twophoton absorption process through an intermediate excited state, leading to the emission of radiation of a higher energy level than that absorbed [41]. The most studied NIR markers are inorganic crystals.…”