Atmospheric Air Plasma Treatment of Plastics

In 2018 almost 36 million tons of plastic waste was produced in the US. This plastic waste makes a small amount of recycled materials (4.4%) but a much larger amount of landfilled materials (18.46%). One of the limiting factors for reusing plastic waste is the difficulty of conversion into usable products. Catalytic thermal treatment of plastic to obtain C2-C4 olefins is one promising method. This work aims to improve this process by plasma pretreatment of the plastics. A pin-to-plate plasma system is used to treat plastic powders within a glass vial and study the surface modifications. The oxidation of the plastics through atmospheric air treatment is expected to improve the catalytic process. The combination of VUV, UV, electron, and ion bombardment modify the surface of the polymer for oxygen absorption both during and after treatment from the oxygen in normal air. This oxidation will be measured and quantified through XPS, contact angle measurements, FTIR spectroscopy, and RAMAN spectroscopy. The plastics polypropylene, polyethylene, polyethylene terephthalate, nylon, and polymethyl methacrylate are treated as powders of varying particle size, molecular weight and density. The variation of the samples gives indication of an optimum size and density for future processing. These plastic powders are also treated in liquid plasma for comparison of the surface modifications.