Co-Pyrolysis of polystyrene and polytetrafluoroethylene: Effects on mass balancing, product distribution and degradation mechanism

Plastic waste generation continues to rise globally, increasing the need for advanced recycling technologies such as pyrolysis. However, the synergistic interactions during co-pyrolysis of mixed plastic streams, particularly those involving dissimilar polymers, are underexplored due to their inherent complexity. To address this gap, this study investigates the co-pyrolysis of polystyrene (PS) and polytetrafluoroethylene (PTFE) under inert laboratory conditions focusing on mass balance, product distribution and the formation of previously unreported compounds absent in the pyrolysis of single polymers. Analytical techniques including gas chromatography–mass spectrometry (GC–MS), Fourier-transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) revealed the emergence of different fluorinated hydrocarbons, falling into the category of per - and polyfluoroalkyl substances (PFAS). Mass spectrometric analysis provided insight into the fragmentation patterns of these unique fluorocarbons. Based on the identified pyrolysis products together with established degradation pathways of PS and PTFE, a plausible reaction network was proposed to rationalize the observed co-pyrolysis products. Additionally, thermogravimetric analysis (TGA) was employed to provide ways to prevent co-pyrolysis behavior through control of heating rate or pyrolysis temperature in order to enable selective monomer recovery. These findings offer a deeper understanding of polymer interactions during thermal degradation and present a framework for studying co -pyrolysis phenomena in mixed polymer systems.