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Decay protection based on moisture exclusion resulting from chemical modification of woodAuthor(s): Rebecca Ibach
Source: Conference proceedings
Publication Series: Full Proceedings
Station: Forest Products Laboratory
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DescriptionSouthern pine solid wood (SPS) and fiber (SPF) were chemically modified to various weight percent gains (WPG) using either acetic anhydride (AA, 4%-19% WPG), butylene oxide (BO, 4%-23% WPG), or propylene oxide (PO, 6%-30% WPG). After modification, part ofthe specimens were extracted with a toluene:ethanol (2:1) solution for 2 hours or water leached for 2 weeks. The equilibrium moisture content (EMC) at 30%, 65% and 90% relative humidity (RH) and 27 °C was determined on all specimens. Laboratory soil block decay testing using the brown-rot fungus Gloeophyllum trabeum was performed and weight loss calculated.
Two possible mechanisms for biological efficacy by chemical modification ofwood have been proposed. One involves lowering the cell wall moisture content below a level required for microorganism attack. The other involves modification ofthe substrate in such a way that the specific enzymatic reactions cannot take place. Results on solid wood indicate that as the EMC is lowered by chemical modifications, biological protection increases. Chemically modified fiber shows a similar trend with AA and BO modifications, but not with PO. Modification of wood fiber with PO does not lower the EMC significantly, even at the highest WPG, yet it imparts biological resistance. This indicates that the mechanism of efficacy may be due to substrate modification.
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CitationIbach, R.E.; Rowell, R.M.; Lee, B.G. 2000. Decay protection based on moisture exclusion resulting from chemical modification of wood. In: Proceedings of the 5th Pacific Rim bio-based composites symposium. Dec. 10-13, 2000; Canberra, Australia. Canberra, Australia: Department of Forestry, The Australian National University: 197-204.
KeywordsChemical modification, acetylation, butylene oxide, propylene oxide, equilibrium moisture content, decay
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