Date of Award
Level of Access Assigned by Author
Master of Science (MS)
Second Committee Member
Third Committee Member
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.
Yelle, Daniel Joseph, "Bonding of Wood Fiber Composites Simulating Natural Wood Cell Adhesion Using Lignin Activation Systems" (2001). Electronic Theses and Dissertations. 873.
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