A Comparison of the Degradation of Mold and Mold-like Fungi on Defined Synthetic Thermoset Polyadipate Polyurethane Coatings

Date of Award

2020

Degree Name

M.S. in Chemistry

Department

Department of Chemistry

Advisor/Chair

Advisor: Justin Biffinger

Abstract

Typical polyester polyurethane coatings, such as those used in military cargo aircraft are susceptible to degradation by mold and mold -like yeasts. These yeasts secrete enzymes which break down the polymer surface via a variety of mechanisms, including hydrolysis. We will use environmental yeast isolated from inside cargo aircraft, Naganishia albida and Papiliotrema laurentii, to determine the overall metabolic activity as it relates to the degradation of a custom polymer coating throughout the degradation process. The custom chain extended polymers will be synthesized from their polyester precursors using published condensation methods. The composition of the polymers will be confirmed using Fourier Transfer Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (1H and 13CNMR), and Gel Permeation Chromatography (GPC). The surface of the polymer coatings will be analyzed with images obtained through Scanning Electron Microscopy (SEM) or optical profilometry. Upon treatment with the two species of fungi, the degradation of the polymers will be documented daily in a 95% humidity environment. The extent of the degradation will be documented using biofilms through scanning electron microscopy images. The activity of the cells on the polymer surface over time will be monitored using a fungal vitality stain (FUN-1) on biofilms with daily imaging using a fluorescence microscope with CCD color camera. The quantification of this staining method for biofilms will be reported based on the number of active cells on the polymer surface throughout the degradation process. The activity of the cells on the polymer surface and extent of degradation will be measured with microscopic and chromatographic methods. The study of polymer degradation is important across many intersecting facets of humanity. As the waste left behind through human consumption continues to pile in landfills as plastics, the discovery of new mechanisms for the degradation of durable plastics and coating materials would be one that would impact billions globally. Alternatively, the ability to produce polymers resistant to degradation over time is appealing for many applications in infrastructure and human safety since the current anti-microbial additives like chromium or zinc salts are environmental hazards. Through this research, we can contribute to the understanding of the longevity of polyester polyurethane coatings in airplanes and their susceptibility to damage by microorganisms that have been found on their surface.

Keywords

Chemistry, Polyester polyurethane degradation, FUN-1 cell vitality staining, Fungal production of melanin, Enzymes that hydrolyze polymers, Papiliotrema laurentii, Naganishia albida, optical profilometry depth profiles

Rights Statement

Copyright © 2020, author

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