Theoretical and experimental research on degradation mechanism of acrylonitrile-butadiene-styrene copolymer (ABS)

Acrylonitrile-butadiene-styrene copolymer (ABS) is a kind of engineering plastic with excellent comprehensive properties, and is widely used in various industries. ABS can be converted into aromatics, aliphatics, and nitriles compound during thermal degradation, but the evolutionary mechanism of these degradation products remains unclear. In this article, ABS dimer, polyacrylonitrile (PAN), polybutadiene (PB), and polystyrene (PS) tetramer are selected as model compounds to investigate the evolution mechanism of the main pyrolysis products by using density functional theory method. The results show that the concerted reaction of HCN elimination by branched chain cleavage has a high reaction energy barrier and may be difficult to occur. The primary reaction pathway is the radical reaction involving the direct cleavage of the C butadiene -C acrylonitrile bond in the main chain, with an energy barrier of 287.1 or 286.3 kJ/mol. The two radicals generated by the initial pyrolysis can undergo further reactions, including β -scission, intramolecular hydrogen transfer, and dehydrogenation reactions. These reactions ultimately lead to the formation of the main products, such as styrene, acrylonitrile, butadiene, α -methylstyrene, and isopropylbenzene. The thermal degradation processes of ABS are investigated at 400, 500, and 600 ℃ by Py-GC/MS analysis. The experimental results of pyrolysis can effectively verify the rationality of the theoretical inference. Based on toxicity assessments, the acute and chronic toxicity of MC4 to aquatic organisms are severe. In addition, the toxicity of the degradation products is lower than that of MC4. These findings indicate that the toxicity of the products to aquatic organisms is significantly reduced.