Oxygen Scavengers in Polyethylene Terephthalate (PET) for Recycled Food Packaging

Bahadar, Hafsa (2025) Oxygen Scavengers in Polyethylene Terephthalate (PET) for Recycled Food Packaging. Masters by Research thesis (MPhil), Manchester Metropolitan University.

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Abstract

The oxidation of diene esters, which mimic the properties of Amosorb®, was investigated to understand the oxidation chemistry of Amosorb®. Model compounds — trans-2,4-hexadienyl acetate (1) and trans-2,4-hexadienyl benzoate (2) — were studied under oxygen in the presence of cobalt (II) stearate at varying concentrations (0 wt%, 1 wt%, and 5 wt%) and timescales. Due to the complexity of Amosorb® analysis, smaller analogues were prepared and studied. The oxidation products were characterized using 1H NMR, COSY, GC, LC, and FTIR after exposure to cobalt (II) stearate for 24, 48, and 72 hours. Key findings indicated that both model compounds oxidized in the presence of cobalt (II) stearate. NMR analysis, with cobalt (II) stearate removed, revealed the formation of epoxides — particularly in model compound 2 — and the formation of aldehydes. These results provide insights into the oxidation products formed from the usage of diene esters for the application of food packaging. Keywords: diene ester, Amosorb®, cobalt (II) stearate, oxygen scavenger, packaging, plastic