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The suitability of isothiazolone microemulsions as long term wood preservatives
1997 - IRG/WP 97-30150
Microemulsion formulations of 4,5 dichloro-2-n-octyl-4-isothiazolin-3-one were investigated to determine the leaching potential of these formulation types as well as their efficacy against decay fungi. These patented low leaching formulations exhibited good anti fungal efficacy in standard tests combined with minimal leaching of the active ingredient from the wood. The data suggests that the excellent long term efficacy ( > 10 yrs) recorded in field tests on solvent borne formulations can be repeated with these emulsion formulations. Active ingredient analysis show an excellent penetration and macrodistribution throughout the samples. Preliminary studies using various instrumental analytical techniques on active ingredient microdistribution at the cellular level show an even distribution throughout the cell wall layers. The data indicates that these microemulsion formulations are an excellent vehicle / carrier for solubilization of a water insoluble biocide, its transport and homogenous distribution into the wood without adversely effecting its permanence or efficacy in the wood during long term service.
B M Hegarty, Bing Yu, L E Leightley

Determination of thermal degradation of isothiazolone treated wood
1997 - IRG/WP 97-30154
Wood treated with 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one was the subject of thermal degradation study. The study included burning isothiazolone treated wood under various temperatures with and without oxygen. The result showed that no harmful combustion products, such as polychlorinated dibenzo-p-dioxins, polychlorinated dibenzo-p-furans and polychlorinated biphenyls, were detected. These findings indicate that isothiazolone treated wood can be safely disposed by incineration.
Bing Yu

Use of X-Ray Fluorescence (XRF) Spectroscopy to Determine 4,5-Dichloro-2-n-Octyl-4-Isothiazolin-3-one (DCOIT) in Wood
2007 - IRG/WP 07-20373
Organic preservative based systems are being developed as replacements for the metal based systems. Typically the chemical actives of organic preservative systems are analyzed using HPLC or GC. However, these analytical techniques require complex sample processing and involve relatively long analysis times. In addition the equipment requires maintenance and a skilled operator. One organic preservative that is currently being developed for a range of uses in wood preservation, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), contains both sulfur and chlorine functionality, providing the potential for the use of XRF for its analysis in both treating solutions and in wood. In this study the applicability of XRF to determine the concentration of DCOIT using the chlorine and sulfur x-ray emissions was determined.
P Walcheski, J Ashmore, D M Laganella

Report of field test results for dichloro-n-octyl-isothiazolone: A potential new wood preservative
1988 - IRG/WP 3495
In a previous report (IRG/WP/3306) we presented preliminary laboratory test results on 4,5-dichloro-2-n-octyl-4-isothiazolone (RH 287). Laboratory data indicated toxic threshold values for RH 287 ranging from 0.37 to 0.50 kg/m³. In this report we present field test results on an IRG L-joint test and an in-ground stake test for RH 287, pentachlorophenol and biocide free test units. (a) L-joint test: After 39 months exposure (Starkville MS.) units pressure treated with 0.05 kg/m³ RH 287 rated 9.7 out of 10. Units dip treated in a 0.5% ai solution of RH 287 rated 10 out of 10. Biocide free controls exposed in the same series rated 5.3 out of 10 after 39 months (b) Stake test: After 48 months exposure in two southern US test plots stakes treated with neat RH 287 in toluene at 4.6 kg/m³ rated between 8.6 to 8.8 out of 10 for decay and 9.1 to 9.8 out of 10 for termite attack. Biocide free control stakes rated O out of 10 for decay and 1.1 to 4.8 out of 10 for termite attack after 48 months. RH 287 continues to show promise as a potential new wood preservative. Results to date were obtained in samples treated with neat RH 287, Formulation of RH 287 into treatment systems specifically designed for above ground or ground contact applications should only improve the already excellent activity seen with RH 287.
D E Greenley, B M Hegarty

Antifungal mechanism of dichloro-N-octylisothiazolone
1998 - IRG/WP 98-30183
4,5-dichloro-N-octylisothiazolin-3-one (DCOI) is a member of the isothiazolone class of preservatives, whose antimicrobial mechanism of action has been intensively studied over the last decade. DCOI has also been intensively studied for use in wood preservation. The isothiazolones are electrophilic molecules that rapidly react with thiol groups to form covalently bonded isothiazolone-thiol adducts. This ability to bond with thiol groups is crucial to their ability to act as preservatives. Thiol groups are present in proteins as part of the amino acid cysteine, where they play an important role in maintaining protein structure and function. A number of enzymes have thiol groups at the site where the enzyme function is performed, and these thiol groups may participate in the enzyme reaction. If the isothiazolone reacts with this thiol group, the activity of the enzyme is inhibited. Our studies have shown that there are several enzymes in the Krebs cycle that are inhibited by isothiazolones and these enzymes are required to generate energy and perform many biosynthetic functions. Reflective of this, DCOI has been shown to be a rapid inhibitor of cellular respiration, causing the cell to cease consuming oxygen almost immediately upon contact with DCOI. The multiplicity of targets and their central importance to the metabolism of the cell, as well as the fact that all microbes use at least parts of the Krebs cycle, can be related to the low use levels and broad spectrum of activity of DCOI. The antimicrobial mechanism of DCOI results in a potent rapid-acting preservative with a broad spectrum of antifungal and antibacterial activity that is effective at low levels.
J S Chapman, M A Diehl, K B Fearnside, L E Leightley

Performance of above ground decay test units treated with a substituted isothiazolone
1989 - IRG/WP 3503
RH 287, a substituted isothiazolone, was evaluated for efficacy against decay fungi in an above ground test in Mississippi. After 45 months of exposure, all test units that were pressure treated with this biocide at levels of 0.026 pcf and higher have no deterioration. In addition, the test units that were dip-treated with a solution concentration of 0.5% also have no deterioration. Compared to penta, RH 287 appears at least 10 times as effective against decay fungi in above-ground exposures. Analytical results from test units exposed for 45 months indicate that RH 287 is stable and does not deplete from the wood.
D D Nicholas, J A Wilson, D E Greenley