Date of Award

Summer 8-3-2016

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Forest Resources

Advisor

Stephen M. Shaler

Second Committee Member

Douglas Gardner

Third Committee Member

Douglas W. Bousfield

Additional Committee Members

Roberto Lopez-Anido

Robert Rice

Abstract

Reducing energy consumption is a high priority in the United States and throughout the world. Energy used to heat and cool occupied constructed facilities is of particular concern, and one of the most effective strategies is insulating the building envelope. Historically, builders used whatever material was available to fill the void between interior and exterior walls, including wool fibers, paper, and even corn cobs. Today, homes are built using foam insulation that harden when applied, blown-in loose insulation, fiberglass mats or rigid foam boards usually composed of polystyrene. Rigid foam boards are used in a variety of applications despite the fact that they typically contain non bio-based materials, require substantial amount of energy to produce, and are not easily recycled. A new “green” insulation material is needed that uses a new raw material and a new process to create its structure. In this study cellulose nanofibrils (CNF) were used as the raw material and industrial corn-starch was used as a binder that uses hydrogen bonding for cross linking to create a successful thermal insulation foam board.

Cellulose, one of the most ubiquitous and abundant renewable polymers on the planet, can be obtained from a variety of sources including trees, agricultural crops, bacteria, and even from animals. The material’s abundance and properties have increased research on cellulose and its derivatives in recent years.

Cellulose nanofibrils are organic polymers that can be obtained through chemical or mechanical methods. The CNF used in this study was produced by the mechanical breakdown of softwood cellulose fibers.

Starch is an abundant green polymer and is a promising raw component for the development of novel materials. However, starch has low mechanical properties. In this research, industrial corn starch was reinforced with CNF suspensions through a unique freeze-drying technique. The research showed significant improvement in the mechanical properties and micromechanical models were created to understand the role of CNF in the composite foam boards. In addition to the theoretical modeling, practical investigation was performed to determine the nanomechanical properties of CNF using an Atomic Force Microscope (AFM) equipped with a Nanoindenter (NI).

This study resulted in successful development of eco-friendly composite foam boards that could be used for thermal insulation and packaging purposes. The nanomechanical properties of CNF were determined, the knowledge and information is a contribution to our understanding of the role of CNF in composite structures. The results of this study show a significant opportunity for using CNF and the data on nanomechanical properties of CNF will provide crucial information to other researchers and industry experts who work on nanocellulose composites and on understanding the role of CNF in the composites.

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