Date of Award

Summer 8-5-2019

Level of Access Assigned by Author

Open-Access Thesis

Language

English

Degree Name

Doctor of Philosophy (PhD)

Department

Forest Resources

Advisor

Mehdi Tajvidi

Second Committee Member

Douglas J Gardner

Third Committee Member

Douglas M Bousfield

Additional Committee Members

Stephan M Shaler

William M Gramlich

Abstract

Being the most abundant natural polymer on earth, cellulose materials have been used in many different applications. Cellulose nanofibrils (CNF) are a relatively new group of lignocellulose resource-based nanomaterials and have been the topic of many research efforts in wood products and material science field over the recent years. Using CNF in textile applications is one way to diversify product portfolio of these materials as they contain nanoscale fibrils with high mechanical properties which can fulfil textile industry’s demand for strong natural fibers. Considering that CNF is a wood-based cellulosic material in the form of water suspension, in order to use these materials for making a product, different aspects of the CNF properties need to be studied. In this work, the potential of cellulose nanomaterials to reinforce other natural fibers in the form of tapes and yarns was investigated. Cellulose nanomaterials showed to improve tensile properties of tapes and yarns of natural fibers while facilitating the drying procedure. In the next step, methods to improve nanocellulose filaments’ properties (without chemical treatments) was studied. The effect of grinding time and fibril fineness on the properties of the final products was studied. A method for the production of continuous filaments from CNF was proposed, which included fast drying of the nanocellulose. Effect of nanofibril fines content and drying temperature on the final properties of CNF was studied. Refining the CNF showed to improve mechanical properties of the filaments. High temperature drying showed to be effective in reducing the drying time while maintaining mechanical properties of the filaments. In the next step, the effects of collection substrate type and surface properties on the cross-sectional form of the final filaments were studied. It was observed that substrate polarity will influence the filament cross-sectional form and applying oil will reduce the interaction between the filament and the substrate and helps increase the circularity of the cross-section. Finally, the orientation of nanofibrils in the filament structure can significantly influence the final properties of the resulted filament. Films of CNF with different orientation were produced and a novel method to measure and map nanofibril orientation in the filament structure was developed. The orientation of the film surface was successfully mapped and the (Birefringence Orientation Index) BOI was measured for the samples with different orientation levels.

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