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SYNERGISTIC WOOD PRESERVATIVES FOR REPLACEMENT OF CCA
Citation:
Nicholas, D. D., T. P. Schultz, AND M. G. Kim. SYNERGISTIC WOOD PRESERVATIVES FOR REPLACEMENT OF CCA. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-99/024 (NTIS PB99-153637), 1999.
Impact/Purpose:
information
Description:
The objective of this project was to evaluate the potential synergistic combinations of environmentally-safe biocides as wood preservatives. These wood preservatives could be potential replacements for the heavy-metal based CCA.
Didecyldimethylammonium chloride [DDAC] was combined with either chlorothalonil [CTN], tribromophenol [TBP] or sodium omadine [NaO] to provide the synergistic mixtures. A total of five systems were examined; one oil-borne [DDAC:CTN] and four water-borne [oil-in-water emulsions] mixtures, including DDAC:NaO with a water repellant. Wood treated with these preservatives was evaluated in both soil contact and above-ground exposures, with CCA and pentachlorophenol (penta) treated wood used as positive controls. The treated wood was evaluated for both biocide efficacy and depletion. Because of project deadlines, the outdoor exposure time was limited to two- to three-years exposure, which is insufficient to fully evaluate the efficacy of most systems.
The water-borne DDAC:TBP and DDAC:NaO formulations performed poorly in the field tests and, consequently, are not viable wood preservative systems. However, the addition of a water repellent to the DDAC:NaO system greatly improve the performance in above-ground tests, suggesting that this may be a good preservative for this application.
The oil-borne DDAC:CTN formulation is performing very well and may be a viable wood preservative system. The water-borne DDAC:CTN formulation is performing moderately well at this time but appears to suffer from excessive CTN leaching; this deficiency probably can be corrected with a modified formulation.