Is it possible to distinguish virgin versus pyrolytic recycled styrene by determining the intramolecular 13C distribution?

Abstract

The accumulation of plastic waste presents a significant global environmental challenge, as these materials are highly resistant to degradation. Polymer recycling offers a promising solution by repurposing plastic waste and reducing reliance on fossil hydrocarbons. Most manufacturing companies that use plastics as raw materials are aware of the societal and environmental issues. With the support of governments, they all are striving to increase the use of recycled materials in the short term, the higher cost of recycled polymers compared to virgin materials (directly derived from petroleum) has led to concerns about counterfeiting. Currently, plastic traceability relies on manufacturers' documentation and declarations, highlighting the urgent need for authentication tools to verify the origin of polymers and ensure the integration of recycled materials in industrial applications. Stable isotopes are widely used to authenticate the origins of various substances, such as pharmaceuticals, food and beverages, and they hold great potential for investigating the provenance of polymers. In this study, virgin styrene and pyrolysis-recycled samples were analysed using ¹³C position-specific isotope analysis performed through nuclear magnetic resonance spectrometry (isotopic ¹³C NMR). The detected ¹³C intramolecular distribution profiles revealed significant differences between the two sources, showing that polystyrene recycling induces an isotope effect. These preliminary findings are highly promising for authenticating recycled styrene. Furthermore, the substantial intramolecular ¹³C composition variations observed in the samples could potentially enable the quantification of recycled and virgin polymers in composite materials.