Improving Wood’s Durability Through Chemical Modification

The impregnation of wood with toxic chemicals is the only method currently used in the field of wood preservation. However, other methods, such as chemical modification of cellulose and modification of minor constituents of wood, show promise. Cyanoethylation of wood is accomplished by impregnating wood with acrylonitrile in the presence of an alkali and heat. The reaction can also be carried out in the presence of a catalyst such as potassium iodide. Chemical analyses of treated blocks showed that a modification of approximately 1 percent by weight of fixed nitrogen is needed to prevent decay. At this level the cost would be several times the cost of commercial treatments now in use. Most fungi require thiamine for growth. Wood contains trace amounts of thiamine and it was shown that destruction of this vitamin inhibited the growth of fungi. The most effective way of destroying thiamine in wood is to heat in the presence of an alkali. Small scale field tests are underway to evaluate the decay resistance of treated wood. Trace elements such as copper, zinc, manganese, iron, and magnesium are required by fungi. Hence removal or inactivation of these elements from wood should impart decay resistance. The use of chemical reactions and chelating agents are suggested as possibilities. Preliminary tests were made with EDTA and at an initial retention of 0.09 pcf of EDTA plus 0.06 pcf of ammonia.

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