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A chemical and mycological evaluation of fused borate rods and a borate/glycol solution for remedial treatment of window joinery
1983 - IRG/WP 3225
The possibility of using fused borate rods (Impel Borpatron) and a borate/glycol solution (Boracol-40) for depot impregnation of window joinery has been examined in a co-operative project between The Swedish Forest Products Research Laboratory, The Swedish University of Agricultural Sciences and Prolignum AB. The fused Impel rod is a glassy rod composed of disodium octaborate which readily dissolves and is distributed as bore acid when introduced into moist timber. Boracol-40 is a liquid containing disodium octaborate dissolved in glycol which has an ability to disperse in timber with a moisture content below 25%. The study involved treatment of a large number of windows in service as well as chemical and biological laboratory tests on the distribution and protective effect of the preservatives. In the field study about 100 windows, selected at random in various buildings in the Stockholm and Gothenburg areas were treated in-situ.
M-L Edlund, B Henningsson, A Käärik, P-E Dickèr


Remedial ground-line treatment of CCA poles in service. Results of chemical and microbiological analyses 6 months after treatment
1986 - IRG/WP 3388
CCA-treated poles in service with incipient internal soft rot were remedially treated by inserting borate rods, brushing with a boron/glycol solution and injecting boric acid paste, copper/creosote paste or a commercial product (DFCK paste). The spread of active chemicals in the treated zone as well as the change in microflora have been studied with time. After six months chemicals had spread to most parts of the pole in the ground-line zone and the microflora had been changed - in some cases drastically. The test is still in progress. Chemical and microbiological analyses after 12, 28 and 60 months will be published at a later date.
B Henningsson, H Friis-Hansen, A Käärik, M-L Edlund


Prevention of Termite Tubing Over Non-Wood Construction Materials Using Glycol Borate
2004 - IRG/WP 04-30358
Glycol borates have been demonstrated to prevent termite tubing and attack of wood materials and are extensively used as termite preventative applications in new construction in the USA. This study evaluated the ability of such systems to prevent Formosan subterranean termite tubing over non-wood materials. Concrete was selected as a common inert construction material and tests were carried out following topical treatment of the concrete with a commercially available glycol borate. It was found that a glycol borate treatment on concrete restricted the ability of termites to construct tubes. Exploratory tubes were less than 20 cm and the treatment caused near complete termite mortality. The results suggest that glycol borates offer a novel approach to protect cellulosic materials within structures not built from wood.
W R Smith, J D Lloyd


Borate Redistribution in Glulam in an Above Ground Field Test
2014 - IRG/WP 14-30652
Researchers have refocused on the use of boratesin the wood protection industry in the last two decades due to their broad spectrum effectiveness against fungi and insects, and favourable environmental characteristics. This study was designed to determine borate distribution in a limited number of samples from a large field test of composites protected by a combination of coating and borate treatment by two processes.The intended application of these products was exterior components of buildings with considerable protection by design, but the test method was designed to be a much more severe exposure. A variety of structural composites had been machined into ɣ-joint test samples, then borate-treated by two methods: a surface-applied penetrating process, and a dip treatment with borate/glycol plus insertion of copper/borate rods.After application of the coating the test samples had been installed in a long-term above-ground outdoor weathering trial at FPInnovations’ Maple Ridge, British Columbia test site. After seven years of exposure, selected glulam beams of black spruce, white spruce, and Douglas-fir samples were destructively sampled and analyzed for borate retention and penetration, with results compared to unexposed material.Results showed that borateshad migrated from the surface of exposed samples to inside the wood, as deep as 50 mm, and in many samples were present in concentrations that would be sufficient to prevent fungal decay.
P I Morris, A Temiz, J Ingram


Preservative Treatment of CLT: An Example at Shimojishima Airport
2019 - IRG/WP 19-30748
Cross laminated timber (CLT) is a relatively new construction method that allows multi-storey construction using solid wood instead of concrete or steel. It is a method favoured by progressive architects and recognized for its much lower environmental footprint. Wood is an excellent construction material and is a long-term carbon sink that also performs well in the event of earthquakes and fire. Obviously being made of a natural organic material, durability performance against mold and wood destroying organisms is a concern. Even if it were possible to permanently keep the wood dry to prevent wood rotting basidiomycete fungi, some pests are able to attack wood that is wetted temporarily (e.g. mold fungi) or even relatively dry wood (e.g. subterranean termites, wood destroying beetles, dry wood termites and carpenter ants. In most parts of the world there is an active remedial treatment market dealing with decay in structures that were also supposed to be kept dry. In the USA damage caused by decay fungi is thought to be even greater that that caused by subterranean termites (Smith and Whitman 2007). The relatively modern use of indoor plumbing and air conditioning has increased interior moisture issues due to water leaks and condensation. In single family residential construction, when problems occur it is relatively easy to carry out remedial treatment of infested structural wood and wood replacement. Even whole structural subfloors sometimes need replacement due to decay caused by high humidity in conjunction with air conditioning. However, it is NOT easy in multi-storey mass timber construction. For this reason, a global representation of wood scientists has discussed this issue and even signed an open letter on the need to address durability of mass timber construction (Taylor et al. 2016). Countries with subterranean termite problems typically have good standards that address them. Soil poisons, primary barrier wood treatments (to a certain height of the structure) and physical barriers, are well entrenched as control methods (Lloyd et al., 2015). However, none of these methods control the other wood destroying organisms. Wood treatment applied to the bottom ~1 meter of a structure was developed originally in Japan and, with glycol borates, is now the leading commercially applied termite preventive treatment in the USA (to meet the US Department of Housing and Urban Development, State and building code requirements). This can be extended to whole house wood destroying organism control (Lloyd et al., 2015). Possible approaches to address durability include the use of naturally durable wood or pressure treatment of wood with appropriate preservatives. A topical treatment (to avoid significantly re-wetting otherwise dry wood) with a diffusible preservative (to move in the event of enough moisture to support decay) and a moldicide may also be adequate. Such treatments could be carried out by spray, dip or double vacuum application and do not typically cause dimension changes (Jermer & Lloyd, 2000). Borates (especially glycol borates for dry wood e.g. Turner, (2008)) have the advantage of being effective against both decay fungi and insects at low retentions (Lloyd, 1997) and are even bait toxicants against subterranean termites at low retention (e.g. Jones, (1991). Such approaches have been successfully used in residential construction such as under the old German Standard DIN 68-800 where lumber was dipped in a 10% disodium octaborate tetrahydrate solution. The use of an inorganic salt as the active ingredient is also good in topical applications where organic systems can be destroyed by UV light during construction (Lloyd et al., 1998). Even non wood destroying insects such as psocids and cockroaches can be controlled via the use of borate treated wood (Lloyd et al., 2003). Borates have low acute mammalian toxicity are globally available from a number of suppliers. To enhance moldicidal performance there are a number of good active ingredients including quaternary ammonium compounds, carbamates, chlorothalonil, azoles and isothiazolinones. An example of such a treatment includes the Arch/Lonza Frame Guard system commercialized in the USA (Lloyd, 2015). Using topical treatments also has the added advantage of being able to change formulations relatively easily (for example you could use different borate concentrations for geographies with and without subterranean termites) and to ensure that all of the construction components are treated (the mass timber itself but also framing and plywood and many other SKUs that typically go into a building. A 40% disodium octaborate tetrahydrate in glycol formulation (commercially available as Boracare from Nisus Corporation) has performed very well in 10- and 15-year field tests in Mississippi (Williams & Amburgey 2003) and Florida (Barnes et al., 2014) against subterranean termites, in preventive and remedial drywood termite tests (Austin & Gold, 2006; Lewis 2012), and in decay tests such as AWPA E 10 (Amburgey et al., 2004). Formal testing was also carried out in Japan as part of the JWPA approval procedure. In addition, a field test was carried out specifically for the Shimojishima Airport project. A separate series of diffusional penetration and rain exposure leaching tests that we carried out in Japan were also useful. Mitsubishi Estate Co., Ltd. organized the construction which was designed by Nikken Sekkei Ltd. architectural office and built by local contractors for Mitsubishi Estate Co. Ltd. The commercial operations of the Airport are carried out by Shimojishima Airport Management Co. Ltd. Topical treatment was carried out using a 40 % DOT glycol borate diluted at a 1 to 1 volume dilution in water (Boracare to equal a 23 % DOT solution concentration). 0.8 % diecyl dimethyl ammonium chloiride (1% as Moldcare available commercially from Nisus Corporation) was added as a surface moldicide. The diluted material was applied with roller coating at Yamasa Mokuzai Co. Ltd., the CLT manufacturer. An application of 300ml m2 was used in compliance with JWPA requirements to treat 6,000 m3 of CLT. This is a higher concentration and higher application rate than required by US EPA registered label against all non-subterranean termite organisms but was chosen to help drive diffusion over time, to give protection against subterranean termites, to enhance spread of flame performance, and to supply some reservoir to compensate for dilution due to diffusion into the wood. All testing and treatment results went well, and the construction is now complete. The inaugural direct flight from Narita to Shimojishima was March 30th 2019 and many more flights will be able to land in an airport that is effectively storing carbon, and will remain free of drywood termites and other wood destroying organisms for the decades to come. If mass timber and especially CLT is to gain the position it deserves in future construction, it is essential that long term durability is addressed. This project has shown that is relatively easy and cost effective to do so.
J Lloyd, N Yamashita, A Taylor


Comparative response of Reticulitermes flavipes and Coptotermes formosanus to borate soil treatments
1991 - IRG/WP 1486
Eastern (Reticulitermes flavipes [Kollarl]) and Formosan (Coptotermes formosanus Shiraki) subterranean termite workers (Isoptera: Rhinotermitidae) were exposed to borate-treated sand in an indirect exposure tunneling assay in the laboratory. In the ten day assay period, both termite species readily penetrated sand containing 5000, 10000, or 15000 ppm (wt. of compound / wt. of sand) disodium octaborate tetrahydrate (Tim-BorÒ) or zinc borate (Firebrake ZB-FineÒ). With Reticulitermes flavipes, significant mortality (85-93%) resulted from workers tunneling through sand treated with 5000 ppm disodium octaborate tetrahydrate (higher concentrations were also effective), or 15000 ppm zinc borate. Responses of Coptotermes formosanus workers were lesser and more variable, with only concentrations of 10000 and 15000 ppm zinc borate resulting in mortality 70-89%) significantly different from that in the control groups. These results suggest that differences between these two species in tunneling behavior may reduce exposure of Coptotermes formosanus to the borate-treated sand.
J K Grace


Borate thermal treatments
1992 - IRG/WP 92-3715
Green, partially seasoned (air-dried, steam conditioned), or kiln-dried southern pine timbers were treated thermally using 15% disodiumoctaborate tetrahydrate solution. After treatment, sections were stored under non-drying conditions to allow for diffusion. Results showed that effective treatment meeting the AWPA minimum retention (0.17 B203 pcf [2.72 kg/m³] in the outer inch) and penetration (2.5-in [64-mm] or 85% of the sapwood) could be obtained only with certain combinations of seasoning, treatment, and diffusion storage. The best results in terms of both retention and penetration were obtained with material steamed and stored prior to treatment using a 10-min hot bath time. Kiln-dried timbers could not be treated effectively. The results suggest that non-conforming treatment of green or partially seasoned timbers will require higher solution concentrations, higher hot bath temperatures, and/or longer diffusion periods to meet required standards. Results also indicated that treatment of smaller stock in dimension sizes (up to 2-in [50-mm]) should be feasible.
H M Barnes, R W Landers, L H Williams


Effect of protective additives on leachability and efficacy of borate treated wood
2002 - IRG/WP 02-30290
Borate preservatives have been used extensively in many countries as an effective means for protecting wood against fungal and insect attack especially in interior environments. Under exterior conditions, borate compounds have a main disadvantage as they can be leached from treated wood as a result of their water solubility. In this study, we compared the potential of different additives for reducing the leachability of boron preservatives from treated wood. Scots pine sapwood (Pinus sylvestris) and poplar (Populus trichocarpa x deltoides) test samples were vacuum treated with 1 % BAE (Boric Acid Equivalent) disodium octaborate tetrahydrate (DOT) solutions containing various additives e.g. glycerol/glyoxal, polyvinylpyrrolidone (PVPY), a commercial resin compound and a commercial water repellent. The European Standard EN 84 was used as a leaching test for both coated and uncoated specimens. The results of chemical analysis of leachates taken at different periods showed that the use of protective additives reduces the boron leachability. The glycerol/glyoxal additive applied to treated pine sapwood showed the best performance. The percent of boron retained in uncoated pine sapwood was 26% while coated samples still retained 45% after 14 days of intense leaching. Similar tests on poplar revealed 19% and 34% for uncoated and coated samples, respectively.This represents a gain of 20 to 25% compared to pure DOT treated specimens of both wood species. Preliminary biological tests were carried out on malt agar using a miniblock technique for uncoated pine sapwood and beech, with Poria placenta and Coriolus versicolor, respectively. After six weeks of exposure to fungal attack all boron protective systems tested proved their effectiveness, as none of the test samples exhibited a mass loss exceeding 4%. The reference 1% BAE without protective additives showed an average mass loss of 15%. Finally, test data are reported of standard EN 113 testing in view of a further evaluation of the biological efficacy of combined DOT-additive treatments.
A Mohareb, J Van Acker, M Stevens


Effects of the addition of polyethylene glycol to the CCA-C preservative treatment
1985 - IRG/WP 3337
A modification of the CCA-C wood preservative system for utility poles has been investigated to see if spur penetration into the poles is assisted during climbing. Addition of polyethylene glycol to the CCA system has been shown to accomplish this purpose. This paper addresses the effects of the addition of polyethylene glycol to other physical properties germane to utility poles.
W P Trumble, E E Messina


Protection of OSB against termites by incorporation of different actives via glue line treatment
2008 - IRG/WP 08-30453
Different organic actives and zinc borate were incorporated into OSB during the manufacturing process to enhance the resistance against termites. Tests according to EN 117 revealed excellent performance of thiacloprid. Other organic actives such as permethrin might be effective when used in higher amounts. Zinc borate failed the test by far.
S Donath, P Spetmann, T Jaetsch, T Zahlmann


Tests on the effectiveness of concentrated borate wood preservative
2009 - IRG/WP 09-30500
Tests were carried out to examine the toxicity of concentrated borate wood preservative to termites, fungi and mammals. The results showed that the preservative treated timber had high resistance to termite or decay and its acute oral toxicity belonged to low grade. The research shows that concentrated borate solution is an environmentally sound preservative and can be used in non-pressure treating.
Su Haitao, Zhang Yanjun, Xie Guijun, Chen Lifang, He Xuexiang


Options for accelerated boron treatment: A practical review of alternatives
1985 - IRG/WP 3329
Boron wood preservatives are almost exclusively applied by momentary immersion and block diffusion storage. Alternative techniques are described which can be used to accelerate boron treatment. Diffusion coefficients have been derived to define the acceleration of diffusion with increasing temperature. Schedules are described for pressure impregnation of green timber, involving steam conditioning, evacuation and alternating pressure method treatment. Timber Preservation Authority penetration and retention requirements can be met in approximately 4-5 h. The optimum schedule, however, included a 12 hour holding period between steaming and preservative treatment. A method of applying boron preservatives as a vapour is described, Trimethyl borate vapour reacts with wood moisture to form boric acid. The kinetics of this reaction, however, are very fast. This limits treatment to timber dried to very low wood moisture contents.
P Vinden, T Fenton, K Nasheri


Movement of boron from fused boron rods implanted in Southern pine, Douglas fir, red oak, and white oak timbers
1995 - IRG/WP 95-30061
This paper reports the distribution of boron from fused boron rods installed into six-inch (15.2 cm) square timbers of Douglas-fir, Southern Pine, red oak and white oak exposed aboveground. The composition and size of rods was: sodium borate and sodium borate-copper oxide (8.5 x 100 mm²); sodium borate-copper, sodium borate and boric oxide-copper oxide (12 x 76 mm²). The boric acid equivalent was roughly monitored by the curcumin/salicylic acid color test and the presence of copper was detected by the chrome azurol-S reagent. One year after installation of rods, movement of boron was determined by application of curcumin dye to increment cores removed at various distances from the site of boron rod installation. A portion of a sodium borate treated Southern Pine timber was also analyzed by spraying curcumin dye on sawed longitudinal and transverse sections. At 2 years, one foot sections were removed from all timber species, sawed as above, and boron and copper detection reagent sprayed on the sawed surfaces. Movement of copper from rods in all timbers was virtually nil. Both transverse and longitudinal movement of boron from rods was greatest in Southern pine which also had the highest moisture content. Movement of boron was next best in red oak. There was little movement of boron away from the rods in white oak and Douglas-fir.
T L Highley, L Ferge


Sequential exposure of borate treated Douglas-fir to multiple Formosan subterranean termite colonies in a 40-week field test
1993 - IRG/WP 93-10006
Douglas-fir boards (ca. 74.5 g) pressure-treated with disodium octaborate tetrahydrate (DOT) retentions of 0 (controls), 0.88, 1.23, 1.60, or 2.10% (weight/weight) DOT were sequentially exposed to four active field colonies of Formosan subterranean termites, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), in an above-ground field test. Samples were placed in contact with each colony for 10 weeks, with oven-dry weight losses determined between exposures, for a total termi exposure period of 40 weeks. Feeding activity differed among termite colonies, with the control wood samples having mean weight losses of 1.3-15.1% of their initial weight during each individual 10-week termite exposure. The two lower borate retentions (0.88 and 1.23% DOT) were virtually equal efficacy, with mean wood weight losses during each individual 10-week exposure ranging from 1.2-4.6%. Feeding was negligible at the two higher borate retentions, with mean wood weight losses from termite feeding during each 10-week period ranging from 0.7-1.3% with 1.60% DOT, and 0.3-0.9% with 2.10% DOT. Total cumulative wood weight losses over the 40 week exposure were: 10.2% (0.88% DOT), 8.7% (1.23% DOT), 3.6% (1.60% DOT), and 2.4% (2.10% DOT).
J K Grace, R T Yamamoto


Diffusion of fused borate rods in top ends of poles
1989 - IRG/WP 3518
Diffusion tests of fused borate rods were carried out on extremities of sapwood poles in service. Rods were set in drills under the cone with or without addition of liquid Boracol 40. After one year of weathering, a good diffusion in the slice under the cone and even below the slice and in the cone itself was observed in Scots pine and spruce poles. The rods were still intacts and constitute, in fact, a reserve of boric acid for the future. This type of treatment would be satisfactory as secondary treatments of poles in service.
D Dirol, J P Guder


The Chemical and Biological Properties of Polymeric Betaine
2009 - IRG/WP 09-30512
Didecyl polyoxyethyl ammonium borate (DPAB), also known as Polymeric Betaine, was developed as a co-biocide for chromium-free copper based wood preservatives in Europe in the 1980’s. DPAB as a wood preservative has been reported previously. This paper summarizes the chemical, physical, and biological properties of DPAB.
H Härtner, S Schmitt, Futong Cui, H M Barnes


Performance if internal remedial treatments to arrest fungal attack in poles and large timbers
2018 - IRG/WP 18-40834
Internal remedial treatments have been used to arrest internal fungal attack in utility poles and other large timbers. Water diffusible systems and volatile fumigants have both been used for this purpose. While both work, it is important to understand the performance attributes of each system. This paper reviews the literature on both systems and makes recommendations for future research.
J J Morrell


The Role of Coformulants in Preventing Bacterial Biotransformation of IPBC
2002 - IRG/WP 02-10436
The inhibitory effects of disodium tetraborate decahydrate and benzalkonium chloride (BAC), two common coformulants of IPBC in antisapstain treatments, on an IPBC-transforming enterobacterial isolate ‘W1’ were determined by their effect on the specific growth rate constant in vitro. The IC50s of IPBC, BAC and borate were found to be 0.46, 0.026 and 5.7 mM respectively. The IC50 of the Arch antistain product AntibluTM Select was 0.024 mM, based on its BAC content. Although their IC50’s were significantly different, it was clear that the vast majority of the bacterial toxicity of the AntibluTM Select was due to its BAC content. The degradation of 0.4 mM IPBC by the bacterium W1, as measured by the accumulation of its degradation product, iodide, in liquid culture, was completely inhibited by BAC concentrations greater than 18 μM, and the toxicity of the spent culture medium to Aspergillus niger, as measured by an antibiotic assay disc assay, was not ameliorated above this concentration. Below 18 μM, the toxicity of the spent broth was significantly reduced, and the accumulation of iodide occurred rapidly. Demonstrating the toxicity of BAC to bacteria, and its consequent inhibition of IPBC degradation in vitro, are indicative of the importance of coformulation in controlling bacteria that might otherwise cause preservative loss, and of their significance in determining the ultimate environmental fate of cobiocides.
S R Cook, D J Dickinson


Emission of trimethyl borate and methanol from radiata pine (Pinus radiata D. Don)
1995 - IRG/WP 95-30088
Sawn and kiln dried radiata pine conditioned to 3, 6, and 12% moisture content was treated with trimethyl borate (TMB). The treated wood samples were placed in mini-desiccators maintained at 20 or 40°C. The air space within the mini-desiccator was analysed for TMB and methanol. An initial period of emission of TMB and methanol was observed. This was followed by a period of gradual dissipation of both TMB and alcohol. There was an equilibrium of 2 ppm and 60 ppm respectively of TMB and methanol for 12% moisture content timber stored at 20°C. Dissipation was slower for 6% and 3% moisture content timber. Higher temperatures resulted in higher concentrations of TMB and methanol during the emission and dissipation stage.
F J Romero, P Vinden, J A Drysdale


Effect of borate on uptake and efficacy of an anti-sapstain treatment
2005 - IRG/WP 05-30380
The potential for using borates to enhance uptake and efficacy of propiconazole-based anti-sapstain chemicals was assessed on ponderosa pine sapwood wafers. Borates had no consistent effect on either net solution absorption or propiconazole distribution in the wood. Even small amounts of borate, however, markedly improved the performance of propiconazole against fungal discoloration. These results are consistent with previous tests of borate addition to other fungicides and highlight the potential for using less expensive ingredients to boost the performance of more costly biocides.
Jianju Luo, Hua Chen, J J Morrell


Potential toxicants for controlling soft rot in preservative treated hardwoods. Part 4: Evaluation of combined diffusion and toxicity
1979 - IRG/WP 2129
A large number of inorganic and organic preservatives were evaluated as potential soft rot control chemicals, by their degree of inhibition of fungal growth after allowing them to diffuse through a 6 mm thick wood slab. The tests were inoculated with wood powder from soft-rotted CCA treated poles. Pentachlorophenol was unable to diffuse quickly through the wood slab, although formulations with hexylene glycol showed some promise. Hydroxyisoxazole gave good results as did a number of other organic materials including "Busan 30", "Busan 52", "Permapruf T", sodium oxinate, sodium trichlorophenate, "Gloquat C", „Hyamine 1622", butyl icinol, and the commercial bandage materials "Osmoplast" and "Wolman pole bandage". Of the inorganic materials tested, good results were obtained with "Basilit BFB", with other Cu-F-B formulations including "Blue 7", and with fluoroborate and fluorosilicate preparations in general. Arsenates also showed some promise.
E W B Da Costa, O Collett


Preliminary evaluation of borate baits and dusts for eastern subterranean termite control
1990 - IRG/WP 1433
Borates are of potential use in the development of baiting systems for subterranean termite control. In the 15-day laboratory assays reported here, the oral toxicity of disodium octaborate tetrahydrate to Reticulitermes flavipes (Kollar) was evaluated under choice and no-choice conditions. These assays suggest a range of 2500 to 5000 ppm to be applicable in developing baits, and that concentrations greater than 5000 ppm may deter feeding. Laboratory assays with borate dusts (disodium octaborate tetrahydrate, zinc borate, and a fine-grain zinc borate) are also reported. In a toxic variation of mark-release methodology, these materials are passed among the test group by grooming foragers exposed to the dust. In these assays, 10% of the test group was exposed to the borate dust, then released placed in contact with unexposed workers in a simulation of a field release. Zinc borate treatment elicited the greatest mortality (99-100%), although disodium octaborate tetrahydrate also elicited mortality significantly greater than that in the control groups. These results suggest that less soluble borates may be more efficient dust toxicants, and that capture and dust-treatment of a portion of the foraging termite population could elicit high mortality among termites contacting the treated individuals after their release back into the colony.
J K Grace, A Abdallay, J M Sisson


Leachability of borate-modified oriented strandboard: A comparison of zinc and calcium borate
2002 - IRG/WP 02-40232
The leachability of boron in zinc and calcium borate-modified oriented strandboard (OSB) was investigated in this study. The leaching experiments were conducted by exposing edge-sealed OSB samples under running water for 8, 24, 72, and 216 hours. The results were compared with those from the unleached controls. Boron leaching of the modified OSB occurred upon the initial water exposure, and the leaching rate decreased as the leaching time increased. Borate type, initial BAE level, wood species, and sample thickness swelling significantly influenced the leachability. There was no consistent effect of polyethylene glycol (PEG) on zinc borate leaching. Calcium borate with a smaller particle size helped reduce its leachability. The glueline washing due to thickness swelling of the test samples under water and decomposition of the borate to form less water-soluble boric acid are thought to be two possible causes for the observed leaching. The relationship between assayed BAE and leaching time followed a decaying exponential function for zinc borate OSB and a Harris decaying power function for calcium borate OSB. The material constants of the regression models allow comparing leachability of the modified OSB for various wood species. A unified leaching method for treated wood composite materials is needed.
S Lee, Q Wu


Ten year field test with a copper-borate ground line treatment for poles
1993 - IRG/WP 93-30017
A wood preservative paste consisting of borax and copper naphthenate has been tested to determine its efficiency in protecting wood from decay fungi and insects. The paste was applied to polyethylene-backed wraps that were fastened to the below-ground portions of unseasoned southern pine pole stubs. After 4 years of exposure in Mississippi, the untreated control stubs were completely deteriorated. The below-grade portions of the treated stubs remained sound after nearly 6 years of exposure due to movement of copper and diffusion of the borate throughout the cross section. Borate and copper also moved vertically in the stubs and was present in sufficient amounts to protect sections of the stubs as high as 3 feet above grade. After 9 years of exposure, the below-grade portions of the treated stubs had limited areas of decay and no termite damage; the majority of the cross section remained sound. Wood analysis indicated that concentrations of borate in the sound areas were about 1/10 the estimated toxic threshold. A visual examination and push test indicated that the treated stubs continued to be protected at groundline after 10 years of exposure. It is hypothesized that the continued protection of the below-grade portions of the stubs against both decay fungi and subterranean termites is the result of copper-borate complexes that have formed in the wood.
T L Amburgey, M H Freeman


A Preliminary Report on the Properties of Engineered Wood Composite Panels Treated with Copper Naphthenate
2005 - IRG/WP 05-40294
This paper reports on our preliminary investigation of the properties of randomly oriented strandboard which had waterborne or powdered copper naphthenate (CuN) incorporated into the board during manufacture. When compared to zinc borate-treated controls (ZnB), the mechanical properties of strandboard (MOR, MOE, work-to-maximum load, internal bond strength) were not adversely affected by treatment with either form of copper naphthenate. In general, values for mechanical properties followed the trend untreated controls > waterborne CuN = powdered CuN > ZnB. Water absorption and dimensional properties followed a similar trend. This preliminary study suggests that CuN is a viable alternative treatment for engineered wood composites.
J W Kirkpatrick, H M Barnes


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