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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

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

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

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

Observations on the colonization of freshly-felled timber treated with prophylactic chemicals by mould and sapstain fungi
1989 - IRG/WP 1394
Field tests using freshly felled pine sapwood were set up to determine the effectiveness of a range of antisapstain compounds and to study the problems of colonization by mould and sapstain fungi. Differences were recorded both in the overall performance of the compounds and also their selectivity in controlling specific fungal types. These results were found to be useful in gaining a better understanding of biocide - fungal interactions.
G R Williams, D A Lewis

Evaluation of substituted isothiazolone as a potential new wood preservative
1984 - IRG/WP 3306
Laboratory decay tests were carried out with isothiazolone (4,5-dichloro-2-n-octyl-4-isothiazolone-3-one) treated wood. This compound was found to be extremely effective against three common wood decaying brown-rot fungi, exhibiting toxic threshold values in the range of 0.37 to 0.50 kg/m³. For the white-rot fungus, Coriolus versicolor, the toxic threshold values for treated pine and sweetgum were 0.42 and 2.3 kg/m³, respectively. In an unsterile soil test (soft-rot fungi), a toxic threshold value of 0.48 kg/m³ was obtained, which indicates a high degree of effectiveness against these fungi.
D D Nicholas, A F Preston, D E Greenley, S V Parikh

Xylophene AS™, the challenge of developing a modern antisapstain formulation for the french market
2000 - IRG/WP 00-30250
In France Sodium Pentachlorophenol (NaPCP) has been used for more than 40 years for the protection of freshly cut and unseasoned lumber. The French sawmill industry requires a protection of 6 months and maximum 10% surface infection by moulds and/or sapstain fungi. However, this active substance did have some serious environmental flaws and no authorisation was granted for a direct contact of NaPCP treated timber with foodstuffs. During the last fifteen years many new formulations were put on the French market for the temporary protection of maritime and Scots pine. Many products gave varying degrees of protection (from a couple of weeks to maximum 4 months) and the required food-contact allowance was not possible with most of these formulations. For those reasons, DYRUP-XYLOCHIMIE put significant R & D resources into the development of a modern antisapstain formulation that met the efficacy requirements of the French industry, which had a favourable toxicological and environmental profile and could obtain a food-contact allowance without restrictions. A close collaboration with active ingredients suppliers such as JANSSEN PHARMACEUTICA NV and TROY CORPORATION was obtained as well. An internal developed field test was used to study the comparative efficacy of several fungicides (azaconazole, propiconazole, tebuconazole, metconazole, IPBC, carbendazim, isothiazolone and quaternary ammonium compounds) against bluestain and moulds. Based on the field efficacy several combinations of IPBC, propiconazole, carbendazim and isothiazolone were finally retained. Official laboratory tests (NF X 41-547) succeeded by internal field tests revealed a good compromise for a new formulation containing propiconazole, carbendazim and IPBC. This formulation was then officially tested according to the French standards : NF X 41-547 laboratory test and NF X 41-549 field test. Toxicological and ecotoxicity data were also gathered and a complete food contact allowance was obtained by the French Ministry of Economy; Finances and Industry. The formulation was then put on the market as XYLOPHENE AS™ and has now been in practical use for more than three years in several French sawmills with satisfactory results.
E Wozniak, L Cubizolles, N Delourme Fonseca, A R Valcke, J Gors

Microemulsion formulations for wood protection chemicals
1993 - IRG/WP 93-30030
A microemulsion is a thermodynamically stable oil-water dispersion system. As a formulation it provides many unique features such as water compatibility for water-insoluble chemicals, formulation stability, good bioavailability and environmental acceptance. This paper discusses the major criteria for the formulations of water-insoluble wood biocides and the comparison in properties between conventional emulsions and microemulsions. Water-dilutable microemulsion technology has been developed at Rohm and Haas Company. Several such microemulsions for a broad spectrum wood biocide, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one, have been evaluated regarding wood penetration and leachability. The results indicated that the active ingredient has a deeper penetration in the wood treated by microemulsions than by emulsion and solvent formulations. The leachability of the active ingredient in this study depends upon the formulation components and will be further investigated.
Bing Yu, L E Leightley

In ground performance of wood treated with a substituted isothiazolone
1990 - IRG/WP 3612
Isothiazolones (I.T.A.'s) are a class of biocides that have potential for use as wood preservatives. The substituted ITA, RH-287, (4,5,dichloro-2-n-octyl-isothiazolone-3-one) is being evaluated as a broad spectrum wood preservative. The evaluation program includes in ground stake tests which were established at two test sites in Mississippi, USA The tests used southern yellow pine treated with RH-287 in accordance with AWPA Standard M7. Five year inspection data have revealed excellent performance by stakes treated with 2 kg/m³ RH-287 in an oil carrier solvent. At this treatment level stakes were protected from termite attack and fungal decay. These results indicate that RH-287 offers excellent potential for use as an in ground contact wood preservative
L E Leightley, D D Nicholas

Effect of an antioxidant on the efficacy of organic wood preservatives in an accelerated soil contact decay test
2012 - IRG/WP 12-30583
In comparison to inorganic wood preservatives, organic biocides in transient carriers are considerably less effective when the treated wood is exposed to soil contact. Various oils are used in some formulations with pentachlorophenol to improve the efficacy. However, use of these oils imparts unacceptable properties to products used in residential applications. Consequently, there is a need to develop additives other than heavy oils that improve the performance of organic biocides as wood preservatives. In this study the possibility of using the benign antioxidant BHT as a non-biocidal additive to improve the performance of wood treated with isothiazolone and azoles was investigated. The treated wood with and without BHT was exposed to unsterile soil and monitored for decay by dynamic MOE. It was found that the efficacy of both preservative systems was enhanced when BHT was added to the formulations. The use of Dynamic MOE to evaluate the progression of wood decay appears to be far superior to visual ratings.
D D Nicholas, J Shi, T P Schultz, L Sites

Termite resistance of copper-based preservative supplemented aspen strandboards
2012 - IRG/WP 12-30594
Termite resistance of aspen strandboards treated with various copper-based preservative systems was evaluated in field exposure tests. Five copper-based chemicals or zinc borate were blended into aspen furnish at three retention levels prior to pressing. Tebuconazole or 4,5-dichloro-2-N-octyl-4-isothiazolin-3-one (DCOI) were added as co-biocides to selected copper-based treatments. Sections from the panels were exposed to a colony of Formosan termite (Coptotermes formosanus) in an American Wood Protection Association Standard E21 test. Incorporating some combinations of copper-based preservative systems with organic co-biocides markedly improved the termite resistance of aspen oriented strandboard.
J J Morrell, C Vidrine, A Preston, L Jin

Effect of biodiesel on Performance of Isothiazolone
2013 - IRG/WP 13-30625
Biodiesel has a number of attractive properties, including the ability to readily solubilize a number of biocides and a tendency to reduce odors associated with other solvents such as petroleum-based diesel. Biodiesels, however, have also been implicated in reduced performance of some, but not all preservatives. It is important to assess the effects of biodiesel on each biocide. Soil block tests were performed on southern pine blocks treated with varying retentions of 4,5-dicholoro-2-n-octyl-4-isothiazolin-3-one (DCOI) with or without soy-based biodiesel. The presence of biodiesel had no consistent negative effect on the performance of DCOI.
Cheng Hua-Kang, L Jin, C Freitag, J J Morrell

Moisture and Fungal Durability of Wood-Plastic Composites Made With Chemically Modified and Treated Wood Flour
2013 - IRG/WP 13-40648
Evaluating the fungal durability of wood-plastic composites (WPCs) is complicated by the influence of slow moisture sorption. Recently, the American Wood Protection Association (AWPA) Standard Method E10, Testing Wood Preservatives by Laboratory Soil-Block Cultures, was modified to incorporate not only solid wood, but also wood-based composites and WPCs. To simulate long term WPC performance, conditioning of the specimens is now required prior to fungal exposure to increase the moisture content of the specimens. The moisture and fungal durability, as well as the mechanical properties, of two different WPCs were investigated in the laboratory following this new AWPA E10-12 Standard. Wood flour was modified with acetic anhydride and then extruded with high density polyethylene (HDPE). Wood flour was treated with an isothiazolone-based solution and then injected molded with polypropylene (PP). WPCs were conditioned by water soaking either 2 weeks at 22 ˚C or 5 days at 70 ˚C. Weight and moisture content of the WPCs were monitored. Results showed that the acetylation decreased the moisture sorption of the WPCs and showed no mass losses due to decay. The WPC with an isothiazolone-based solution did not show any mass losses due to fungal decay.
B K Segerholm, R E Ibach