Date of Award

Spring 5-5-2023

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Forest Resources

Advisor

Douglas J. Gardner

Second Committee Member

Jinwu Wang

Third Committee Member

Mehdi Tajvidi

Additional Committee Members

Douglas W. Bousfield

William Gramlich

Abstract

Food packaging provides means to mitigate food spoilage caused by microbes and environmental exposure, as well as prolonging the shelf life of food products in a cost-effective manner that industry and consumers desire while minimizing environmental impact. However, conventional plastics are unsustainable, nonrenewable, as well as nondegradable, and coupled with single-use culture can cause serious environmental pollution and the loss of resources. Taking the above issues into consideration, bio-based materials with the required properties are desirable to address the end-of-life issues for packaging.

Cellulose nanocrystals (CNCs), as a major type of cellulose nanomaterials are directly extracted from renewable biomass resources and have tremendous potential in the packaging field as a natural material. However, CNC films are too brittle to use singularly and extremely sensitive to moisture or water, which restricts the practical use of CNCs in food packaging applications.

The main goal of this dissertation was to fabricate environmentally friendly CNC films with high performance as a promising substitute for plastic food packaging. We thoroughly studied the water vapor sorption behavior and gas transport of CNC films. CNC films adsorbed more moisture with increases in relative humidity (RH) and temperature, respectively. The oxygen permeability of CNC films exhibited an exponential increase above 50% RH. We successfully developed transparent CNC films with UV-light absorption, water and oxygen barrier properties, oil resistance, and fire self-extinguishment via trivalent metal ion exchange. We also prepared functional CNC films by incorporating different concentrations of sorbitol, polyvinyl alcohol, carrageenan, and chitin nanofibers. The films exhibit good oxygen barrier, mechanical properties, and water durability. Additionally, we manufactured multilayer PLA (poly lactic acid)-CNC-PLA films by mixing CNC suspensions with 15 wt.% polyvinyl alcohol or carrageenan coating on PLA substrate, followed by lamination without any petroleum-based tie layer or adhesive addition. These three-layer laminate films exhibited enhanced barrier properties and the PLA film protected the inner CNC film from water and mechanical damage. This research provides practical concepts for commercially eco-friendly, recyclable, high-performance food packaging production.

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