Date of Award

2001

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Forest Resources

Advisor

Barry Goodell

Second Committee Member

Douglas Gardner

Third Committee Member

Aria Amirbahman

Abstract

Wood fibers, after thermo-mechanical defibration, have a high concentration of lignin on the outer surface of the fiber. This outer surface is the residual middle lamella of the woody cell wall. When wood fibers are oxidatively treated with a chelator from Gloeophyllum trabeum, a brown-rot fungus, in the presence of hydrogen peroxide (H202) and ferric iron (Fe III), the free radicals produced may attack the surface lignin and other phenolic based compounds promoting reactions with themselves as well as other nucleophiles such as cellulose and hemicellulose. This chelator is a low molecular weight molecule that binds and reduces metals to facilitate the sustained production of hydroxyl radicals through a 'Fenton' mechanism. Activating the lignin and/or extractives on the surface of the wood fibers, which has been shown previously by chemical and enzymatic means, can give lignin the functionality of a self-bonding adhesive. Therefore, the need for conventional adhesives is eliminated. In preliminary work, fiberboard produced with a pre-treatment by a model Gt-chelator, 2,3-dihydroxybenzoic acid (DHBA), showed an increase in the internal bond strength over that of fiberboard without DHBA pre-treatment. In this research, wet and modified dry-process fiberboard increased in internal bond, modulus of rupture, and modulus of elasticity with DHBA pre-treatment over that of fiberboard without DHBA pre-treatment. The strongest boards were with a mM 1:10 ratio of DHBA:Fe III with peroxide. A mM 0:10 ratio of DHBA:Fe III displayed a similar bond and bending strength to the mM 1:10 ratio, suggesting that natural chelators in the wood are reacting similarly to low concentrations of DHBA in a Fenton-chelator mechanism. Reference fiberboard made from urea-formaldehyde resin, however, performed better than the Gt-chelator fiberboard in mechanical properties. Positive results from this system could lead to reduction in adhesive costs and less reliance on petroleum-based adhesives.

Download

Files over 10MB may be slow to open. For best results, right-click and select "save as..."

Share