Characterization of Plastic Additives and Recycled Plastics
Analytical methods for additives and quality assessment of food contact materials containing post-consumer plastics
Time: Fri 2026-09-18 10.00
Location: F3 (Flodis), Lindstedtsvägen 26 & 28, Stockholm
Video link: https://kth-se.zoom.us/j/62801728373?pwd=zAOo41X23mbnGcb0aIstUNLoj5p1su.1
Language: English
Subject area: Chemistry
Doctoral student: Xiaoning Shen , Kemi
Opponent: Professor Ulrika Nilsson, Stockholm University
Supervisor: Professor Åsa Emmer, Tillämpad fysikalisk kemi; Doktor Hany Anwar, Norner Research AS
QC 20260819
Abstract
The recycling and reuse of post-consumer resins remain challenging due to complex mixtures of additives and non-intentionally added substances (NIAS) introduced or formed during use and recycling. This thesis combines mass spectrometry-based method development for plastic additives with the safety assessment of recycled polyethylene terephthalate (PET) used for food contact materials (FCM).
Liquid chromatography mass spectrometry was used to investigate the solvent-associated species of a benzofuranone antioxidant (Paper I). Their formation influenced chromatographic retention, ion abundance, and fragmentation, particularly in positive ion mode. Negative ion mode provided more structure-dependent and interpretable fragmentation, demonstrating its value for complex additive analysis.
Characteristic ions in tandem mass spectroscopy enabled the identification of hindered amine light stabilizers (HALS)-related species, although their low sensitivity limited direct application in quantitative analysis (Paper II). Combining precursor ions and base-peak product ions improved the estimation of total HALS content in polymers.
The effects of recycled content, processing history, and PET morphology on NIAS profiles, contaminant levels and uptake were investigated (Paper III and IV). Processing and manufacturing influenced volatile NIAS and contaminant levels. Acetaldehyde and benzene were found in PET materials but at low concentrations in simulants after migration tests, suggesting limited health concerns. Challenge tests assess decontamination by exposing PET to surrogates before recycling. Conditions used in challenge tests could alter PET morphology, in turn, affecting contaminant diffusion and complicating estimates of decontamination efficiency.
This thesis shows that analytical conditions, polymer properties, and processing histories are critical for interpreting chemical profiles in recycled plastics, and supports reliable additive and NIAS investigation, and safety evaluation of FCM.