Surface chemistry of degraded polyethylene terephthalate (PET): Insights from reactive molecular dynamics study

Abstract

Polyethylene Terephthalate (PET) samples were analyzed using reactive molecular dynamics simulations. These samples consisted of polymer molecules with a molecular weight of approximately 20,000 amu. The simulations employed ReaxFF reactive force fields designed for CHO systems within the combustion branch. Material properties, such as density, Young's modulus, and Poisson's ratio, were determined through stress–strain curve analysis. These results aligned well with experimental data. The PET samples were subjected to mechanical cleaving by applying external forces to generate PET surfaces. These surfaces were further investigated to assess their chemical composition and the quantity and types of radical ends formed on them. Benzene radicals and dioxolane residues were the most abundant species identified on these surfaces. In addition, the samples underwent shock compression to induce more extensive chemical transformations, resembling naturally degraded nanoplastics. This led to the discovery of various crosslink connections within the bulk material, with many appearing as new chemical linkages or radicals on the surfaces. Notably, there was a significant production of carbon dioxide observed during both the mechanical cleaving and shock compression of PET samples. An important conclusion is that the chemically degraded PET surfaces are significantly different from the original material.