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|Author:||Juan Jacobo Paredes Heller|
|Title:||The Influence of Hot Water Extraction on Physical and Mechanical Properties of OSB|
|Committee Chair:||Stephen M. Shaler, Professor of Wood Science, Advisor|
|Committee Members:||Adriaan van Heiningen, Professor of Chemical Engineering ; Douglas J. Gardner, Professor of Wood Science ; Robert Rice, Professor of Wood Science ; Barbara Cole, Professor of Chemistry|
|Subjects:||Engineered wood; Extraction (Chemistry)|
|Date of Defense:||2009|
The finite reserves of petroleum are driving renewed interest in technologies that allow for sustainable production of energy. There are a wide variety of technologies with well-developed infrastructure like the oriented strand board (OSB) industry, which could be used as launch point for developing biorefineries. The effects of hot water extraction (HWE) on two hardwood species (Acer rubrum, Populus tremuloides) and softwood species (mixture of southern yellow pine, Tsuga canadensis) were studied. The HWE resulted in a weight loss (WL) that increased as the severity factor (SF) was extended. Hardwood had the biggest WL values at equivalent extraction conditions. The extract contained a mixture of primarily hemicelluloses with some acetic acid and lignin. Select volatile organic compounds from the hot pressing of OSB panels were reduced by HWE of the strands. A clear advantage with extracted OSB panel (softwood or hardwood) for structural use is the improved dimensional stability and physical properties obtained as SF was increased. The mechanical property (MP) of composite for softwood was enhanced while for hardwood was reduced. Substantial improvements in MP were obtained at the intermediate SF (12% WL). When SF was extended beyond the optimum MP declined as measured by a cell wall test in both species. These changes are hypothesized to due to an increase in the percent crystallinity of cellulose. The increase in crystallinity was correlated to the MP, but the effect was less than of SF. Mechanical response was also affected by chemical component changes, micro- buckling, the reduction in moisture content and the reduction adhesion properties. Dispersive surface energy of red maple increased with SF due to extractive removal while that the contact angle measurement showed rapid penetration of probe liquids due to increases of porosity as a result of mass removal at high extraction conditions (over 15% WL). Basic characteristic related by IGC measurements could directly affect the chemical reaction between the resin and wood elements of hardwood species. For all these reasons, the recommended extraction for softwood should be below 12% WL and an improvement of resin system for hardwood species. The ability to manufacture lower density panels with same size and mechanical properties appears feasible to compensate for the material extracted.
Paredes Heller, Juan Jacobo, University of Maine, FTY2009-001