Title:
Cost-Effective, Aqueously Degradable Poly(Ethylene Terephthalate) Films Containing a Latent Metal Oxide Reagent
Cost-Effective, Aqueously Degradable Poly(Ethylene Terephthalate) Films Containing a Latent Metal Oxide Reagent
Author(s)
Duprez, Natalie
Advisor(s)
Luettgen, Christopher
Yao, Donggang
Yao, Donggang
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Abstract
The widespread use of plastics, combined with their durability and persistence in the environment, has created a tremendous environmental burden. Flexible packaging in particular, including films and polymer coatings, has a particularly low recycling rate. Substantial efforts have been made to replace these typically single-use materials with biodegradable options, but high costs, difficulties with processing, and unsuitable mechanical properties often prevent their widespread use. In this work, polyethylene terephthalate (PET), one of the most affordable and commonly used plastics available, is made to be degradable by the addition of CaO via melt-mixing. This allows the PET to undergo alkaline hydrolysis upon exposure to water, ultimately converting to ethylene glycol and calcium terephthalate (CaTP), a salt of terephthalic acid. Due to the inert nature of CaO relative to other alkaline reagents, it may be mixed into PET and processed without hydrolyzing the polymer chain, and the material undergoes degradation only in the presence of water. In this work, this latent hydrolysis reaction is studied via the full and partial degradation of PET/CaO composite films at different concentrations and temperatures. The films were seen to be able to hydrolyze completely in water, forming the expected CaTP product, given that there was adequate CaO to drive the reaction to completion. Identification and observation of intermediates in the series of degradation reactions validated the proposed mechanism for latent degradation. Based on the proposed mechanism, a kinetic model was developed to predict the conversion of PET depending on key system parameters. The observed trends could be explained logically and generally followed experimental results, indicating that the rate equations provide a good starting point for describing this system.
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Date Issued
2022-12-08
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