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Natalie Duprez
Advisors: Prof. Luettgen and Prof. Yao will defense a master’s thesis entitled,
Aqueously Degradable Poly(ethylene terephthalate) Films Containing a Latent Metal Oxide Reagent
on
Tuesday, November 22 at 11:00 a.m. Paper Tricentennial Building Room 521
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 degrades 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. Testing and characterization of the samples
verified that the alkaline reagent CaO does not degrade the PET during processing, but instead
reduces thermal degradation. 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. This model
was shown to describe the behavior of the system and provide more of an understanding of how to
control the reaction via formulation and degradation conditions. While films were used to study the
degradation reaction, it was also shown that this composite may be applied as a coating to a paper
substrate. This may be done to allow the coating to be more easily removed to recycle the paper. In
fact, once adequate degradation was achieved, the polymer coating was easily removed, demonstrating
the potential benefits of using this composite material as a coating.
Committee
• Prof. Christopher Luettgen – School of Chemical and Biomolecular Engineering
• Prof. Donggang Yao – School of Materials Science and Engineering
• Prof. Carson Meredith – School of Chemical and Biomolecular Engineering
