Treatment of Wood with Polysilicic Acid Derived from Sodium Silicate for Fungal Decay Protection


  • George C. Chen


Fungal decay protection, impregnation, moisture sorption, polysilicic acid, surfactant property


The aim of this study was to investigate safer, more inexpensive chemicals derived from sodium silicate that can be used to protect wood against fungal degradation. Desiccant and surfactant properties of sodium silicate-derived products have been used since the early 19th century and may find application for wood decay protection. In our study, wood was impregnated with 19.5% sodium silicate and acidified with 2.5% phosphoric acid for 2 da to produce polysilicic acid. After 2-wk daily water leaching, leached specimens had 0.2% weight loss by a brown-rot fungus, Gloeophyllum trabeum, and weight losses of 3.4-5.2% by a white-rot fungus, Trametes versicolor. The control had 32.2 and 30.2% weight losses by G. trabeum and T. versicolor, respectively. Energy-dispersive X-ray analysis showed that polysilicic acid deposited mainly in the cell lumens. Exposure at 90% RH showed that polysilicic acid-treated loblolly pine or sweet gum that had been water-leached with 22-34% chemical retention absorbed more moisture than untreated wood. This indicated that decay resistance of polysilicic acid-treated wood is caused by a different mechanism than desiccation. One possible mechanism may be attributed to direct disruption of permeability of fungal cell membranes by the low-molecular-weight polysilicic acid.


ASTM (2000) Standard method of testing wood preservatives by laboratory soil-block cultures D1413-99. Volume 4.10. American Society of Testing and Materials, West Conshohocken, PA. Pages 218-224.nColthup NB, Daley LH, Wiberley SE (1964) Chapter 10. Ethers, alcohols, and phenols. Pages 269-277; Chapter 12. Compounds containing boron, silicon, phosphorus, sulfur, or halogen. Pages 291-318. In Introduction to infrared and raman spectroscopy. Academic Press, New York, NY.nDomagk G (1935) Ein beittrag zur chemotherapie der bakteriellen infektionen. Deut Med Wochschr 61:250-253.nEaton RA, Hale MDC (1993) Wood: Decay, pests and protection. Chapman & Hall, New York, NY. Pages 319-343.nEitel W (1954) The physical chemistry of the silicates. The University of Chicago Press, Chicago, IL. 1592 pp.nFuruno TK, Shimada T, Uehara T, Jodai S (1992) Combinations of wood and silicate II. Wood-mineral composites using water glass and reactants of barium chloride, boric acid and borax, and their properties. Mokuzai Gakkaishi 38(5):448-457.nGezer ED, Yalinkilic MK, Kizilkaya K, Michael JH (1999) Estimation of preservative toxic threshold retention from laboratory decay tests: A new method. Wood Sci Technol 33:63-71.nGoodwine W (1990) Suitability of propiconazole as a new generation wood preserving fungicide. InProc American Wood-Preserver's Association. 86:206-214.nGreen F III, Henry W, Schultz TP (2002) Mechanisms of protection by NHA against fungal decay. The International Research Group on Wood Preservation. IGR/WP 02-10429.nGreenley DE (1986) Laboratory and field evaluation of a substituted isothiazolone as a potential wood preservative. InProc American Wood-Preserver's Association. 82:1-10.nHubard SS (1954) Silica and silicates. Encyclopedia of chemical technology. Vol. 12. Encyclopedia, Inc., New York, NY. 955 pp.nLee HL (1998) Evaluation of phosphoramides to improve thermal and fungal resistance of wood. University of Wisconsin-Madison, Madison, WI. PhD Diss. 280 pp.nLos Angeles Times (2002) Wood with arsenic to be phased out. 13 Feb. 2002. Pages 1-4.nMarchessault RH (1962) Application of infra-red spectroscopy to cellulose and wood polysaccharides. Pure Appl Chem 5:107-129.nMcComick AV, Bell AT, Radke CJ (1987) Quantitative demonstration of siliceous species in sodium silicate solutions by silicone-29 NMR spectroscopy. Zeolites 7(3):183-190.nNance WN, Amburgey TL (1976) Statistical analysis of data from laboratory decay tests. InProc American Wood-Preserver's Association 72:161-171.nNicholas DD, Preston AF (1980) Evaluation of alkyl ammonium compounds as potential wood preservatives. InProc American Wood-Preserver's Association 76:13-21.nReisch M (2002) Getting arsenic out of wood. Chemical and Engineering News. 11 Feb 2002. Page 9.nSchultz TP, Nicholas DD (2002) Development of environmentally-benign wood preservatives based on the combination of organic biocides with antioxidants and metal chelators. Phytochemistry 61:555-560.nSteel RGD, Torrie JH (1960) Principles and procedures of statistics. Pages 332-345 in Non-linear regression analysis. (Steel and Torrie, eds). McGraw-Hill Book Company, Inc., New York, NY. 666 pp.nSvensson IL, Sjoberg S, Ohman LO (1986) Polysilicate equilibria in concentrated sodium silicate solutions. J Chem Soc, Faraday Trans 182:3635-3646.nValcke AR, Goodwine WR (1985) Azaconazole, A new wood preservative. InProc American Wood-Preserver's Association 81:196-202.nWeber CF, Hunt RD (2003) Modeling alkaline silicate solutions at 25°C. Ind Eng Chem Res 42:6970-6976.nWillis JH (1954) Soluble silicates and synthetic insoluble silicates, Encyclopedia of chemical technology. Vol 12. The Interscience, Inc., New York, NY. 955 pp.nWoods T, Bell J (1990) Development of chlorothalonil as a wood preservative. InProc American Wood-Preserver's Association 86:190-196.n






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