Date of Award

12-2008

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Chemical Engineering

Advisor

Douglas W. Bousfield

Second Committee Member

Douglas J. Gardner

Third Committee Member

Michael D. Mason

Abstract

Nanotechnology has the potential to help create materials with novel properties. Most nanoparticles are from expensive materials or require high processing costs. Cellulose nanofibcrs have the potential to be a low cost material that can be produced in large quantities from a renewable resource. The goal of this work is to reduce the production costs of cellulose nanofibcrs from wood fibers using both mechanical and enzyme treatments. The resulting nanofibers diameters are characterized using atomic force microscopy. Bleached kraft softwood fibers are pretreated with a mechanical method that uses a dispersion mill and with two different enzymes before being processed through a homogenizer, in which the sample is forced through a small orifice under high pressure. The resulting fiber sizes are characterized with an atomic force microscope. The maximum solids that could be processed by the homogenizer are also determined. Both pretreatment methods, by themselves, did not generate a significant amount of fibers below 100 nm. Even for untreated fibers, most of the fiber disruption occurs during the first three passes through the homogenizer. The mechanical pretreatment did not change the average fiber size, but allowed an increase of 0.5% solids to be processed. Enzyme pretreatment allowed an increase of 1.5% solids to be processed without clogging. Both enzymes give a smaller diameter than the untreated fibers at low number of passes, but one enzyme results in smaller fibers at lower number of passes than untreated fibers and the other enzyme. This enzyme also increases the solids that could be processed. An enzyme dose of 1% per weight of the suspension is found to be optimum. Using both the dispersion mill and the enzyme does not change the resulting fiber size, but does increase the solids through the homogenizer to 2.5%. Initial estimates indicate that the energy savings by using the enzyme more that cover the cost of the enzyme.

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