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Silicic acid-Boric acid complexes as wood preservatives
2001 - IRG/WP 01-30273
A silicic acid monomer aqueous solution (SAMS) or colloidal silicic acid solution (CSAS) was combined with various metal compounds or boric acid. Agents where SAMS or CSAS was combined with boric acid gave good protection against decay caused by the brown-rot fungus Fomitopsis palustris, the treated wood (Cryptomera japonica D. Don) specimens after the leaching test maintained a high resistance to decay. The leaching and decay tests revealed high quantities of chemicals leaching from wood treated with SAMS-metal agents. However, when wood was treated with SAMS-boric acid, there was little leaching of agent in either test. The mechanism of resistance of wood, which was treated with boric acid mixed with CSAS or SAMS, to the brown-rot fungus F. palustris were investigated. When the concentration of boric acid was high, mycelial growth was inhibited completely and no protein production was detected. When the amount of boric acid was low, the xylanase, mannase and cellulase activities were lower than with control wood powder. When wood was treated with silicic acid only, its resistance to termites increased, but not to the marked extent observed after treatment with a mixture of silicic and boric acids. Also, increasing the quantity of boric acid increased the mortality rate of termites, and shortened the time to death. From field tests on stakes over three years, it was shown that even if stakes were placed near the termite exit, those treated with silicic acid and high levels of boric acid maintained their original form. Combustion tests showed that with high levels of boric acid, flaming and glowing combustion times were shortened. When boric acid-methanol solution was added at of rate of not less than 25 ml for 100 ml of CSAS, flaming and glowing combustion were not observed. Though the charring length of the wood- specimen, which was treated with silicic acid¡boric acid agent, decreased to 1/3 of that of control wood, the charring lengths were not influenced by the level of boric acid. However, the volume of smoke decreased relative to the amount of boric acid that had been added. When powdery boric acid was combined with CSAS, it was considered that the treated woods have higher anti-weather properties than when boric acid-methanol solution was mixed with CSAS. The agent- preparation method adopted should be considered carefully after taking the treatment process and the intended use of the preservative-treated wood into account.
Influence of Acetylation on Fire Resistance of Beech Plywood
2006 - IRG/WP 06-40326
Influence of acetylation on fire resistance was studied in beech plywood. Beech layers were acetylated in a reactor with acetic anhydride at 120ºC for varying durations. Plywoods were made from the acetylated layers and directly exposed to burning flame from their edges for 60s according to ISO 11925-3. Ignition and glowing time were measured in samples. Results were analyzed statistically based on a complete randomized design to determine effect of the acetylation on fire resistance. Results indicated that the acetylation affects ignition and glowing in plywood. Ignition time was increased due to raised weight percent gains and glowing was decreased instead. The acetylated plywood was burning with short blue flames; while flame was long and yellowish in non-acetylated one. This study revealed that the acetylation retards slightly fire in plywood; however it does not resist wood against fire.
B Mohebby, A Talaii, A Karimi , S Kazemi Najafi