(Re)upcycling of Acrylonitrile-Butadiene-Styrene (ABS) via Nitrile Reduction and Imine Vitrimer Formation

Plastic consumption has increased significantly in recent years, leading to a corresponding rise in waste generation. Bioplastics account for only about 1% of the 360 million tonnes of plastic produced each year. Most plastics persist in the environment for 100-1,300 years, and even bio-based types show limited natural degradation. Engineering plastics, such as acrylonitrile-butadiene-styrene (ABS), are derived from petroleum sources and find applications in various industries, including automobiles, aerospace, electrical, and electronic equipment (EEE). The sudden increase in global electronic waste production reached ~59 million tons, with less than 17% recycled. ABS accounting for about 30% of the total waste electronic and electrical equipment (WEEE) makes it a significant contributor to the plastics fraction, further increasing waste generation. Herein, we report the upcycling of ABS through nitrile reduction, a path to vitrimer formation. The nitrile groups in ABS undergo selective reduction using a boron catalyst, yielding an amine-functional ABS, ethenamine butadiene styrene (EABS). Imine crosslinking with glutaraldehyde leads to the formation of an imine-based vitrimer, imine butadiene styrene (v-IBS). v-IBS, a dynamic covalent network that unites thermoset-like stability with thermoplastic reprocessability. Analysis via FTIR spectroscopy demonstrates the chemical transformation, and thermal-mechanical tests reveal an apparent difference in properties: with a Tg of 115 ℃ and a tan δ peak of 145 ℃, consistent with an increased network. Stress-relaxation tests (120-150 ℃) exhibit Arrhenius behavior with Ea = 146 kJ/mol, indicating thermally induced imine exchange. Gel fraction tests revealed complete dissolution of ABS in THF (0% mass retained), whereas v-IBS 0.25 and v-IBS 0.40 retained 90% and 93% of their mass after 24 h. These results demonstrate that nitrile functionalization, followed by dynamic crosslinking, provides a synthetic route to upcyclable ABS. The insolubility confirms the formation of a robust crosslinked network. Acid-catalyzed hydrolysis in DMF regenerates EABS, showing reversibility and supporting a route where ABS is converted to EABS, vitrimerized, and decross-linked to recover EABS. These features highlight desirable properties for use in polymer laminates, composites, and fiber reinforcement. The intended goal is to promote innovative reuse, thereby fostering a sustainable and green environment.