Antioxidant-Containing\nPolymeric Additives for Improved\nMechanical Recycling of PET

Functional additives such as antioxidants\nand chain extenders\nare\nimportant mitigators of the thermo-oxidative degradation that occurs\nduring the high-temperature reprocessing of poly(ethylene terephthalate)\n(PET), yet leaching of these additives into packaged goods or the\nenvironment can pose risks to environmental or human health. In this\nwork, we prepared a series of polymeric antioxidants with molar masses\nin the range of 3–12 kg/mol by free radical copolymerization\nof styrene (<b>S</b>) and 2.5–10 mol % of a phenol-containing\nmethacrylate monomer (<b>BHM</b>). These additives were incorporated\ninto PET via extrusion, and we investigated their ability to impart\noxidative stability as well as their propensity to leach into solvents\nof different polarities. Additive performance was benchmarked against\nthat of Irganox 1010, a commercially available phenolic antioxidant,\nand Joncryl ADR 4400, a polymeric chain extender that rebuilds polymer\nchains through cross-linking. Extrusion trials revealed similar performance\nbetween all polymeric additives and Irganox 1010, whereas oxidative\ninduction time (OIT) tests revealed that the 5–10 mol % incorporation\nof <b>BHM</b> afforded similar or better performance than Irganox\n1010, with little to no dependence on the polymer molar mass. Minimal\nleaching of the polymeric antioxidants was observed in methanol, whereas\nexperiments in acetone revealed that ca. 3 kg/mol polymers leached\nbetween 2 and 5 times more than their ca. 12 kg/mol counterparts across\nall polymer compositions. This systematic study provides valuable\ninsights for the design of future antioxidants that effectively stabilize\nrecycled plastics without increasing risks to the environment or human\nhealth.