Semester

Spring

Date of Graduation

2011

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Wood Science and Technology

Committee Chair

Jingxin Wang.

Abstract

Cellulose is an abundant, low cost, and robust biopolymer that is possible to implement in reinforcement of composite materials. Utilizing cellulosic nanocrystals, which can be isolated from cellulose fibers, nanocomposite biofilms are currently of interest to the packaging, medical, and pharmaceutical industries. At this time, hardwood cellulosic nanocrystals and nanocomposites are understudied. Therefore, this research characterized and examined the possibility of using hardwood residues for nanocomposite formation and implementation. Red oak (Quercus rubra) heartwood and sapwood residues were collected from 2005, 2006, and 2007 harvest sites located within West Virginia and were de-lignified by acidified sodium chlorite. Cellulosic nanocrystals were then isolated from the de-lignified red oak residues through a combination of sulfuric acid hydrolysis, ultrasonication, and homogenization. Upon isolation, nanocrystals were combined with a polyvinyl alcohol (PVA) matrix to form fully biodegradable cellulosic nanocomposite biofilms, via film casting. Morphology and thermal gravimetric results indicated that while de-lignification was a success, nanocrystal isolation was only partly successful, with some amorphous cellulose and lager cellulosic microfibrils remaining within the suspensions. Thermal gravimetric data also revealed that the composites experienced thermal degradation behaviors quite similar to their constituent materials. Tensile mechanical properties (strength and elastic modulus) of the nanocomposites were improved when compared to neat PVA; however, these increases in strength were coupled with decreases in elongation to break behaviors. Water vapor transmission rates were significantly decreased at the 2% and 6% loading levels, with the use of highly crystalline cellulose. Constructed composites did not hinder water vapor transmission at the 10% crystal loading level. Solubility testing revealed that cellulosic nanocomposites were able to remain intact at a wide range of temperatures, while being submerged in water, unlike neat PVA. All data found during this research suggested that any differences in properties of cellulosic nanocomposites, can be attributed to the initial processing methods used for nanocrystal isolation, not the year (2005, 2006, and 2007), or type (heartwood and sapwood) of materials used for biofilm formation. These materials are expected to be very useful for packaging and food barrier devices that are safe to the consumer and biodegradable. Formation of cellulosic nanocomposite biofilms utilizing red oak residues will benefit the wood industry by incorporating previously wasted materials into new environmental friendly products.

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