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The Role of Phosphorus Flame Retardants in PET Thermal Degradation
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Date
2025
Publication Type
Doctoral Thesis
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Abstract
The circularity and sustainability of polyethylene terephthalate (PET) containing phosphorus flame retardant (PFR)s have long been a formidable challenge. The chemical reactions between PET and PFRs during mechanical recycling lead to unpredictable degradation of the properties of recycled materials. To advance the development of recyclable and sustainable PFRs for polymeric materials, this thesis uses PET compounds modified with two model PFRs, combining experimental techniques and computational modeling, to demonstrate the processing and mechanical performance of such materials and uncover the underlying chemical mechanisms. The experimental characterization tools, such as compounding, rheometry, thermal analysis, and tensile testing, allow for exhaustive observations of the microscopic structural changes and macroscopic performance of various PET compounds. The experimental work reveals how PFRs differently influence PET’s behavior during processing, affecting both rheological and mechanical properties. A key strength of this thesis is the unique combination of advanced computational modeling, specifically reactive force field molecular dynamics (ReaxFF-MD) simulations and density functional theory (DFT) calculations, with experimental data. The recycling performance of PET PFR compounds was evaluated experimentally. DFT calculations assessed the unimolecular bond dissociation processes and protonation, while the ReaxFF-MD simulations were employed to advance the understanding by integrating additional factors, such as intermolecular interactions, oxidative conditions, and polymeric systems. By combining experimental analysis and computational approaches, the roles of different PFRs in the recycling of PET were discovered, and the major reaction events in the PET PFR were identified. This thesis seeks to provide insights into the complex interplay between PET and PFRs and outlines future directions for improving PET recycling and the design of recyclable PFRs.
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Examiner : Heuberger, Manfred
Examiner : Passerone, Daniele
Examiner : Vermant, Jan
Examiner : Holzer, Clemens
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Subject
Polymer degradation; Flame retardant; Polyethylene terephthalate (PET); Mechanical recycling; Melt-spinning; Density functional theory; Transition state theory; Molecular dynamics; Reactive force field
Organisational unit
01314 - DR Materialwissenschaft / DR Materials Science