Distribution of preservative chemicals in flakeboard and its effect on board properties and fungal deterioration Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/zs25xb43z

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  • Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] lumber was converted to flakes, which were dip treated with three concentrations each of copper chrome arsenate Type C (CCA-C), and disodium octaborate tetrahydrate (TIM-BOR). Azaconazole [1-[{2-(2,4-dichloropheny1)-1,3- dioxolan-2-yl}methyl]-1H-1,2,4-triazole] was used as powder. The flakeboard panels (305 x 304 x 13 mm) were made using phenolformaldehyde powdered resin and wax. Distribution of CCA and TIM-BOR in treated flakes and panels was examined using x-ray fluorescence and titration methods. Concentrations were greater in the ends of flakes than in the center. Scanning electron microscopy with energy dispersive x-ray analysis (EDXA) showed that CCA distribution was quite uniform on the surfaces examined. Concentrations of CCA and TIM-BOR in selected panel zones were uniform, indicating that the chemicals did not migrate significantly during panel manufacture. Distribution of azaconazole was not examined because a reliable method was not available. In water leaching test. CCA and azaconazole were found to be resistant to leaching, while TIM-BOR was not. Samples were tested for decay resistance using the soil block and vermiculite burial tests. Trametes versicolor, a white rot fungus, and Phialophora heteromorpha, a soft rot fungus, caused very low weight losses and did not appear to actively colonize even the untreated controls. Postia placenta, a brown rot fungus, caused substantial weight losses in untreated controls. With the latter fungus, CCA performed better than azaconazole and TIM-BOR, producing the lowest weight loss. The highest weight losses were associated with TIM-BOR, although some of the weight loss may have resulted from leaching during the decay test. The effect of each test chemical on dimensional stability, static bending and internal bond (IB) properties of treated panel was evaluated. When exposed to hot wet conditions, TIM-BOR treated samples had large thickness swell compared to CCA and azaconazole, and often delaminated. Samples placed in hot dry conditions had very small dimensional changes over time. In static bending and internal bond tests, strength reductions for TIM-BOR and CCA treated samples were clearly evident; however, reductions for TIM-BOR treated panels were greater than those for CCA. Azaconazole showed no deleterious effect on strength and generally performed well. A discussion of needs for future research is included. Those include a fundamental understanding of the interaction of preservative chemical within flakes and mats prior to pressing, during pressing, and in service. In addition, the need to establish more appropriate means to evaluate the effectiveness of treatment is identified Environmental safety, both during processing and in-service, is also identified as an important factor.
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