ATR-FTIR Investigation of Plastics Treated by Atmospheric Pressure Plasma*

The growth of plastic waste in modern society is unsustainable and there are large scale environmental and human health consequences. Chemical upcycling of plastic wastes is an emerging strategy to combat this environmental problem. Using innovative techniques such as plasma decomposition plastics can be broken into value-added chemicals, ex. CO, C2H2, used in chemical synthesis . Plasma decomposition of plastics through pyrolysis and hydrogenolysis, produces monomers and oligomers allowing for the formulation of new high quality compounds. Three different plastics polymers, Polypropylene (PP), Polyethylene Terephthalate (PET), and Low Density Polyethylene (LDPE), were exposed to Ar plasma at atmospheric pressure with additions of H2 and N2. After treatment, the remaining solid materials were analyzed via Fourier Transform Infrared spectroscopy (FTIR) with an ATR accessory. The treated PET showed little measurable changes after plasma exposure, but PP showed increased oxides. Additionally, the PP and LDPE treated in the Ar/H2 mixture showed the break up into smaller chains than when treated with Ar alone. The addition of N2 resulted in LDPE, there is evidence of oxides and nitrates with the presence of nitrogen gas. The presence of short fragments in the LDPE and PP with the addition of H2 gas provides evidence for hydrogenolysis as a decomposition process in plasma treatment of plastics.
Acknowledgement:
The work of Dorothy Doughty was supported by the Student Undergraduate Laboratory Internship and SS was supported by the Princeton Collaborative Research Facility, supported by the US Department of Energy, contract no. DE-AC02-09CH11466.