Date of Award

Fall 12-15-2023

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Forest Resources

Advisor

Mehdi Tajvidi

Second Committee Member

Islam Hafez

Third Committee Member

Douglas W. Bousfield

Abstract

In recent times, plastic has become a highly favored choice for packaging due to its exceptional microbial, damage, and water-resistant properties. However, the alarming rise in plastic usage has led to adverse environmental pollution. This study aims to develop innovative food packaging solutions using renewable and compostable cellulose nanofibrils (CNFs). This thesis comprises two related studies on the barrier performance of novel food packaging materials, including oxygen barrier and oil/grease barrier properties. The goal of the first study was to enhance the mechanical and barrier properties of the cellulose nanofibril (CNF) films by inducing fibrils orientation for food packaging applications. To attain the alignment, CNF films were produced using an auto dynamic sheet former (ADSF) by varying the wire speeds as well as the solid contents of CNF suspension. The wet films were dried using restrained (Z_Z shrinkage) and non-restrained (XY_Z) methods. The tensile strength and tensile modulus (E) of the ADSF-produced films were tested in the machine and cross-direction and were found to be higher for Z_Z films compared to XY_Z films at 1000 m/min and 1100 m/min wire speeds with an average anisotropy ratio of 1.4, depending on the drying method. The films made at a wire speed of 1100 m/min exhibited the highest oxygen barrier properties regardless of the drying method. Polarized light microscopy (PLM) was used to quantify the film’s orientation but proved inadequate for measuring the alignment of the entire film. The study found that by optimizing the solids content of the CNF suspension and the wire speed of the machine, it is possible to achieve alignment of native CNF films. Applying a shrinkage drying method can further enhance this alignment, leading to the possibility of producing renewable food packaging materials with enhanced oxygen barrier properties. The second study focused on developing a CNF-laminated wood veneer food serving container as an alternative to plastic and molded fiber containers containing per- or poly-fluoroalkyl substances (PFAS). In this study, two CNF films were attached on both sides of the wood veneer using a food-grade polyamide-epichlorohydrin (PAE) as an adhesive. The containers were formed by hot pressing the wood veneer with CNF films at 140 °C and 160 °C temperature and 0.08 MPa or 0.16 MPa pressure for 3 or 5 min. The mechanical properties of the containers were compared with wood veneer hot-pressed at 160°C temperature, 0.16 MPa pressure for 5 min. The flexural properties of the composites were measured both in parallel and perpendicular to the grain direction and showed an impressive increase compared to the wood veneer control sample (without CNF layers). The thermogravimetric analysis (TGA) results showed that the crosslinking between CNF and the PAE was susceptible to degradation at lower temperatures, which may explain the trend of decreasing peel strength with increasing treatment parameters. The containers showed excellent oil, grease, and water barrier properties, which demonstrate that these CNF-wood veneer composites can be used as safe, eco-friendly food-serving containers.

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