Chemical Characterization of Plastic Thermal Degradation Products Using Temperature Programmed Desorption − Direct Analysis in Real Time − High-Resolution Mass Spectrometry
EMILY HALPERN, Peter Christ, Killian MacFeeley, Lauren Heirty, Christopher P. West, Yitao Li, Won Kim, Anthony Mennito, Alexander Laskin, Purdue University
Abstract Number: 361
Working Group: Chemicals of Emerging Concern in Aerosol: Sources, Transformations, and Impacts
Abstract
As the global demand for plastic grows, plastic management has become an environmental concern. Plastic burning processes are used as methods of disposing of plastic waste; however, plastic thermal decomposition releases a complex and poorly understood mixture of air pollutants that can condense into secondary organic aerosol. There is a pressing need to develop and implement efficient techniques to study the thermal decomposition of plastic samples. Here, we employ temperature-programmed desorption-direct analysis in real-time high resolution mass spectrometry (TPD-DART-HRMS) in both positive and negative ion modes to study four kinds of plastic standards, and three kinds of plastic wastes. CH2 Kendrick mass defect (KMD) grouping was used to identify characteristic trends in the mass spectra acquired from each of the plastic samples and to better identify the products released during plastic thermal breakdown for common types of plastic: polyethylene, polypropylene, polystyrene, and polyvinyl chloride. We developed a statistical method based on the Tanimoto coefficient to compare the thermal decomposition products of unknown plastic waste with those of the plastic standards. Additionally, we were able to study the complex mechanisms of plastic thermal degradation. Arrhenius plots of extracted ion chromatograms (thermograms) were employed to deduce the apparent activation energies of thermal degradation of various products broken down and volatilized from polymer macromolecules of plastic. These values enable us to model gas-phase emissions from thermal decomposition of plastic and evaluate their propensity to form SOA in emissions from plastic burning events.