Plasma Assisted Depolymerization of Polyethylene Terephthalate*

Currently, the world is facing a plastics crisis, with only ~10% being recycled. In this work, we investigate the use of nonthermal plasmas to assist in the chemical recycling of polyethylene terephthalate (PET) (a consumer plastic used in packaging), promoting depolymerization which can be upcycled into commodity plastics or other high value products. PET may be depolymerized into precursors terephthalic acid (TPA) and ethylene glycol (EG) in a liquid with heat, pressure, and/or chemicals (strong acids or bases) by hydrolysis.  Nonthermal plasmas in contact with water can provide non-equilibrium conditions at the interface such as heat, UV, solvated electrons, a host of reactive oxygen and nitrogen species (ROS/RNS) and localized pH changes. These conditions are suitable to provide several pathways for polymer chain breaking, including hydrolysis, without the typical required heat and chemicals to alter the pH. This initial work aims to provide insight on the bulk conditions of the solution created during treatment, including plasma and gas temperature, ROS/RNS concentrations, and pH changes. Polymer analysis techniques, including mass spectrometry, FTIR, and Raman spectroscopy are used to understand reaction products as well as functional groups formed at the polymer surface.