Graduate Thesis Or Dissertation
 

Moisture Resistance of Wood-Based Composite Materials

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/p26772486

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  • Dimensional stability of wood-based composites with changing moisture content remains an important challenge in the industry for many applications. Wood modification technologies have shown significant improvement in dimensional stability by altering the chemistry of the wood substrate, or by filling the available space in the wood microstructure that otherwise would be occupied by water. There are commercial and non-commercial modified wood composites materials that have been reported to exhibit high dimensional stability, however, the testing methodology among them usually differs, which makes the direct comparison between material types inappropriate. The main objective of this research project was to study the effectiveness of several wood modification technologies when exposed to moisture. Four medium density fiberboard (MDF) and five plywood materials were exposed to liquid water from above, high relative humidity, liquid water from below, and cyclic exposure to investigate the effect of each material type and exposure type on thickness swelling (TS), linear expansion (LE), irreversible thickness swell, and initial rate of dimensional change. Acetylation of MDF and impregnation of plywood with phenol-formaldehyde (PF) or 1.3-Dimethylol-4.5-Dihydroxyethylenurea (DMDHEU) resin have shown the lowest thickness swelling values. The mean TS values for MDF materials after 192 h of water spray exposure were approximately 3%, 11%, 14%, and 21% for the acetylated, heat-treated, steam-injected, and MR10 MDF, respectively. The mean TS values for plywood samples were 4% for plywood impregnated with PF or DMDHEU resin, 6% for the heat-treated plywood, and 10% for the untreated plywood. The LE values of the acetylated MDF were also the lowest within the MDF group, with an average value of 0.17%, whereas the heat-treated plywood resulted in the lowest LE values in the plywood group, with an average of 0.12%. The initial rate of thickness change was lower in the MDF group than plywood, with an estimated value of 3.4 %/h for the acetylated MDF and 8.8 %/h for the untreated Baltic birch plywood.
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  • Intellectual Property (patent, etc.)
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  • 2020-06-26 to 2021-07-26

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