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Incorporation of phenyl boronic acid treatment with vapor phase formalization
1997 - IRG/WP 97-40083
Phenylboronic acid (PBA) treatment was incorporated with vapor phase formalization (VPF) in order to increase dimensional stability and boron fixation as well as enhancement of biological resistance. Five and ten hours VPF were applied after PBA treatment as 0.34, 0.50, 1.00 and 2.00% concs. aqueous solutions. Anti swelling efficiency (ASE) attended to 71% in specimens impregnated with 0.50% PBA solution followed by five hour VPF. Leachability test results were supportive to presume a possible chemical bonding of PBA and formaldehyde. Decay test results indicated that formalization imparts superior properties to PBA treated wood against test fungi Tyromyces palustris and Coriolus versicolor, each as brown- and white-rot fungus, respectively. Fungal attack was completely inhibited with five hours of VPF and PBA treatment at the lowest loading level in the study. Shorter formalization seems also appropriate to attain the required fungicidal effectiveness with a little amount of PBA retention. Weight loss caused by Formosan termite Coptotermes formosanus Shiraki could be lowered by PBA-VPF treatment system, in addition to considerable increase in termite mortality.
M K Yalinkilic, S Yusuf, T Yoshimura, W-Y Su, K Tsunoda, M Takahashi


Effect of boron compounds-furfuryl alcohol treatment of wood on dimensional stability, termite resistance and boron leachability
2001 - IRG/WP 01-40195
Sapwood blocks of Japanese cedar (Cryptomeria japonica) and Caribbean pitch pine (Pinus caribaea) measuring 20 (tangential) x 20 (radial) x 10 (longitudinal) mm were impregnated with furfuryl alcohol (FFA) by a vacuum-diffusion process followed by curing under heating. Boron compounds (boric acid, ammonium borate and ammonium biborate) were mixed in the impregnation solution of FFA. Anti- swelling efficiency, water holding capacity and moisture exclusion efficiency were measured. Boron leachability was determined by ion chromatography with ten leaching cycles according to JIS 9201 (1992). The specimens were exposed to termite attack testing, before and after the cyclic leaching process. The results indicated that FFA imparted to wood greater dimensional stability when mixed with boron compounds. Boron when mixed with FFA behaved differently to boron alone treatment, although it was still leachable. The wood specimens treated with FFA-boron compounds were quite resistant to termites even after severe leaching.
S K Ozaki, M K Yalinkilic, Y Imamura, M F Souza


Leachabilty and efficacy of fatty acid derived boron esters as wood preservatives - leachability and efficacy of fatty acid derived boron esters as wood preservatives
2004 - IRG/WP 04-30351
Borates have many advantages as wood preservatives. However, boron is susceptible to depletion under humid conditions and this restricts its outdoor use. In order to reduce boron leachability in treated wood, one of the anticipative approaches is to use organic fixed boron-based preservatives. This study investigated the leachability of six boron ester compounds as potential preservatives. Scots pine sapwood (Pinus sylvestris L.) test specimens were vacuum treated at different concentrations of BAE (Boric Acid Equivalent) of each boron ester active ingredient with and without 10% addition of commercial resin product. Stand-alone boron treatment using 1% BAE disodium octaborate tetrahydrate (DOT) is conducted as a reference. The results of chemical analysis of leachates taken at different periods showed significant differences in boron leachability between the DOT treated samples and specimens treated with both boron esters. Although there are significant differences between the pure boron treatment and the resin protective addition treatment, minor differences were found between boron ester treatments irrespective of resin addition. However, these data allowed the selection of one boron ester compound for further biotesting based on its leaching performance. Results of the biological assays with both Scots pine sapwood and poplar (Populus trichocarpa x deltoides) samples using the European standard EN 113 confirmed the efficacy of the selected boron ester compound against Coriolus versicolor, Coniophora puteana, Gloeophyllum trabeum and Poria placenta. After sixteen weeks of exposure to fungal attack all specimens treated with the new organic boron compound at 0.66 % BAE, irrespective of resin addition, exhibited insignificant mass loss for all four fungi and both wood species tested, which proved the decay resistance of the treated wood.
A Mohareb, J Van Acker, M Stevens


Influence of hydrophobic agents on the leachability of boron
1995 - IRG/WP 95-30064
Besides its low mammalian toxicity and a broad range of activity towards both fungi and insects, boron shows a high diffusibility, encouraging it to treat wood species of low permeability. However, its difussibility is at the same time responsible for a high risk of leaching, known since long. Nevertheless quantitative data about this process are only rarely available. Therefore, the leaching of boron under different conditions and possible means of hydrophobising boron treated wood in order to reduce leaching were investigated by laboratory and field tests. For this purpose paraffin and a primer have been applied to protect the inner surface and alkyd-resin and a varnish as surface coat. The results demonstrate that boron diffuses even at moisture contents below 20%. Thus leaching can not be affected by hydrophobic agents placed on the inner surface of wood because diffusion still takes place within the cell-wall. Surface coatings have some protective effect but only during a distinct periode which is depending on the thickness of the coat. With time leaching increases with increasing moisture content underneath this coat. The best way to prevent leaching is the logistical protection by storing and using boron-treated wood exclusively under cover. Only for a short periode, for example during construction, a surface protection with waxes or resins will be effective.
A Peylo, H Willeitner


Borates as wood preserving compounds: The status of research in the United States
1989 - IRG/WP 3542
This paper describes the extensive, on-going cooperative research effort among government and university research laboratories and industry to fully evaluate the potential for borates as wood preservatives in the United States. Research is discussed in terms of laboratory evaluations, field testing and mill trials, pilot plant pressure treatment studies, and remedial treatments. Future research plans are also presented.
H M Barnes, T L Amburgey, L H Williams, J J Morrell


Synthesis of boric acid ammonium oleate salt for wood preservation: Leachability and termite resistance test
2007 - IRG/WP 07-30435
A new chemical compound coupling boric acid and oleic acid through a joint of ammonium salt has been produced and its synthesis followed and validated by Fourier Transformed Infra Red (FTIR). This compound named ammonium borate oleate (BAO) combining biocidal properties of boron and water repellence of fatty acids has then been studied as a wood preservative. Synthesis of BAO involved different molar rates of oleic acid to determine the best formulation regarding boron retention and resistance to termites. Formulations including four moles of oleic acid for one of boric acid and one of ammonia (1:1:4) have shown the best efficiency compared to formulations 1:1:1, 1:1:2 and 1:1:3 with about 52% of boron remaining after weathering when other formulations retained respectively 10%, 29 % and 46% of boron in the case of an impregnation of Japanese cedar sapwood specimens. Seven solutions of 1:1:4 BAO in ethanol of different concentrations were then produced and impregnated sapwood blocks of C.japonica and F.crenata exposed subterranean termites Coptotermes formosanus. Toxicity threshold around 2.0 Kg/m3 BAE for F.crenata and 2.4 Kg/m3 BAE for C.japonica are a bit lower than toxicity thresholds found in previous studies from 2.0 to 4.5 Kg/m3 BAE indicating that boron is available despite its combination with fatty acids. Extremely low mass losses indicate a positive effect of this combination, hydrophobic effect of oil reduces termite attack and boron leaching when boron provides a biocidal protection. Termite mortality rates recorded along the three weeks of exposure precised the action mechanism of BAO as an intermediate between biocidal boric acid and non toxic fatty acid. Termite mortality rates increase with BAO concentration but an inflexion occurs for highest concentrations due to high oil content.
F Lyon, A Pizzi, Y Imamura, M F Thevenon, S N Kartal, J Gril


The Comparison of Fixation and Leachability of Bark, Fruit and Leaf Tannin Extracts with Boron Minerals
2008 - IRG/WP 08-30473
Tannins extracted from several plants have natural durability properties. Due to these properties, some of the researchers have studied them for protecting wood. In this study, Scots pine (Pinus sylvestris) and beech (Fagus orientalis) wood samples were treated with bark, fruit, and leaf extracts as well as water-based wood preservative salts at various concentrations to increase fixation. The penetration, fixation, and antifungal properties of different treatment solutions were compared. Retention levels were generally higher for Scots pine wood than beech wood. The highest retention levels were seen in wood treated with valex and sumex, which are extracts of oak fruits and sumac leaves, respectively. Leaching tests indicated that both wood types treated with sumac extracts showed higher retention levels than wood treated with the other fruit and bark extract solutions. Adding 1% water-based wood preservative salts to valex and sumac extracts increased the retention levels. Higher concentrations of wood-preserving salts accelerated and increased the amount of leaching. We found that the extract alone was resistant to leaching. Mycological tests showed that bark extract solution was the most effective at preventing mycelium penetration and that adding water-based wood-preservative salts to all extract solutions significantly affected the resistance of the wood against fungal infection.
S Sen, C Tascioglu, K Tirak


Effects of new fixative additives on leachability of boron wood preservatives
2009 - IRG/WP 09-30507
Borates are well known with their protective capacity against both fungi and insects with low mammalian toxicity and environmental acceptable. However, boron itself does not ensure the appropriate protection for wood in the exterior applications because of their easily depletion from the treated wood under wet conditions. In this study, the potential use of monoglyceride and polyvinyl alcohol products as boron fixative agents was investigated. Two levels of these selected compounds (10%, 15% for the monoglyceride and 2.5%, 4% for the polyvinyl alcohol) were evaluated separately with three boric acid equivalent concentrations (1%, 2% and 4% BAE) in double vacuum impregnation processes using Scots pine sapwood and European beech specimens. Leaching was performed according to a laboratory leaching procedure (ENV 1250-2). Results of boron analysis using atomic absorption spectrometer (AAS) for the wood specimens and the leachates showed a significant reduction in boron leachability for the samples treated with both tested fixation additives when compared to the stand-alone boron-treated specimens. For boron protective additive treatments, the percentages of residual boron ranged from 20% – 37% of the initial boron retention. In all cases for these treatments, the detected boron retentions were above the toxic limit (1 kg BAE/m3) set for wood protection against basidiomycete fungi. Polyvinyl alcohol additive was the most promising product with approximately the same boron fixation effect but at lower levels when compared to the high levels of the tested monoglyceride compound.
A Mohareb, J Henry, E Wozniak, P Gérardin


Effects of polyvinyl alcohol on leachability and efficacy of boron wood preservatives against fungal decay and termites attack
2010 - IRG/WP 10-30526
In this study, the use of polyvinyl alcohol (PVA) as boron fixative agent was investigated. Two levels of PVA (2.5 and 4%) were evaluated with disodium octaborate tetrahydrate (DOT) at three concentrations (1, 2 and 4% boric acid equivalent (BAE) using a double vacuum impregnation processes on Scots pine sapwood specimens. Leaching was performed according to a laboratory leaching procedure. Boron analysis using atomic absorption spectrometer showed a significant reduction in boron leachability for the samples treated with both concentrations of PVA when compared to the stand-alone boron treatment leading to boron retentions capable to prevent wood biological degradations. Decay resistance of the leached specimens was evaluated using the brown rot fungus Poria placenta. Even if complete protection was not fully achieved, an improvement of decay resistance was observed for the samples treated with DOT in presence of PVA. This leak of efficacy was attributed to a decrease in the biological activity for the complexed boron against fungi. Durability of treated wood against termites attack, evaluated using Reticulitermes santonensis, indicated a significant enhancement for the samples treated in presence of the fixative agent comparatively with the pure boron treatment.
A Mohareb, M F Thévenon, E Wozniak, P Gérardin


Smart hydrogels from low molecular weight amphiphilic compounds: toward a solution to decrease leachability and increase efficacy of boron preservatives?
2012 - IRG/WP 12-30589
A new catanionic system associating amphiphilic carnosine (AlaHisC8) and lauric acid forms supramolecular hydrogel at very low concentration. This gel was investigated and we have checked the validity of the concept of hydrogels utilization to reduce boron leachability and to develop new wood protection treatments. Impregnation with 5% aqueous borax solution (w/w) and 0.3% gelator agent (w/w) allows to improve resistance of Scots pine sapwood subjected to water leaching towards the brown rot fungus Poria placenta, while samples treated with 5% aqueous borax solution were partially degraded by the fungus. These results clearly indicate the effectiveness of hydrogel to retain boron in wood.
F Obounou Akong, P Gérardin, C Gérardin-Charbonnier


Hydrogels: a solution to reduce boron leachability without reduction of its biodisponibility to wood decaying fungi?
2012 - IRG/WP 12-30602
Products used today for wood protection must fulfill to more and more environmental constraints, such as being of low toxicity in answer to the Biocidal Product Directory, but also to involve waterborne treatments to limit rejection of volatile organic compounds in the atmosphere. Boron preservatives have been described as valuable alternatives for wood protection for non-ground contact applications. Disodium octaborate tetrahydrate (DOT), boric acid and borax are the most widely used boron-based wood preservatives. They possess many advantages such as being colourless, odourless, non corrosive, non flammable, inexpensive, having low vapour pressure and low toxicity for mammals and the environment, but suffer of an important drawback due to their high susceptibility to leaching which limits their use in outdoor applications. Numerous studies have been described to reduce boron leachability involving mainly the use of organic chemicals to reduce boron solubility in water through formation of insoluble or hydrophobic complex. However, complexation reduced boron biodisponibility to fungi, limiting the application of such complex to develop antifungal treatment. The objective of this work was to design supramolecular hydrogels, built on low-molecular-weight amphiphilic molecules and containing boron salts conferring fungicidal properties. Mixing boron with thermoreversible hydrogels allows the formation of a supra molecular network incorporating boron and important amount of water upon gelification of the solution when the temperature decreases. Hydrogels obtained from several amphiphilic peptides, pseudo-peptides or various gelling molecules of the same type were impregnated in pine wood block using vacuum pressure treatment and subjected to leaching. Results indicated that incorporation of boron salts in the hydrogel network, allowed to protect effectively wood from degradation caused by the brown rot fungus Poria placenta even after leaching. It was assumed that these hydrogels are able to fill the cell walls and the lumina of the tracheids limiting the leachability of boron salts when the wood is subjected to re-humidification.
F Obounou Akong, P Gérardin, M-F Thévenon, S Parant, C Gérardin-Charbonnier


State of progress of utilisation of supramolecular gels for formulations of water-soluble wood preservation salts
2013 - IRG/WP 13-30630
This article is a compilation of the work done so far concerning the utilization of supramolecular hydrogels, built on low-molecular-weight amphiphilic molecules and containing boron salts conferring fungicidal properties. Mixing boron with thermoreversible hydrogels allows the formation of a supra molecular network incorporating boron and important amount of water upon gelification of the solution when the temperature decreases. Hydrogels obtained from several amphiphilic peptides, pseudo-peptides or various gelling molecules were impregnated in pine wood block using vacuum pressure treatment and subjected to leaching. Results indicated that incorporation of boron salts in the hydrogel network, allowed to protect effectively wood from degradation caused by the brown rot fungus Poria placenta even after leaching. It was assumed that these hydrogels are able to limit the leachability of boron salts.
F Obounou Akong, P Gérardin, M-F Thévenon, C Gérardin-Charbonnier


Aspects of diffusion of boron through wood
1984 - IRG/WP 3298
Boron compounds have been shown to be toxic to a wide range of wood destroying insects and fungi. They are cheap, have low mammalian toxicity and their application in the treatment of wood does not demand specialized equipment. These attributes make them specially attractive to developing countries. Currently, however, little is known about the mechanism of diffusion of boron through wood. Effective treatment with boron preservatives requires good understanding of how the preservatives diffuse through wood. This paper presents a research proposal with the overall objective of determining the relative importance of structural wood components in determining diffusion rates.
S Iddi


Utilization of curcumin for detection of presence of boron in wood
1982 - IRG/WP 3191
It has been shown that curcumin is not a reliable reagent for detecting boron in wood that has been attacked by fungi
M-L Edlund


Strength loss associated with steam conditioning and boron treatment of radiata pine framing
1987 - IRG/WP 3438
The combined effect of included defects and wood moisture content on the strength loss of second rotation radiata pine framing following conventional steam conditioning is investigated. The green Modulus of Elasticity (MOE) is reduced by approximately 13% after steaming. When dried after steaming, however, neither the MOE nor MOR is significantly different from unsteamed dried controls.
M J Collins, P Vinden


Synergistic effect of boron on Streptomyces rimosus metabolites in preventing conidial germination of sapstain and mold fungi
1992 - IRG/WP 92-1565
We evaluated the synergistic effect of boron (4% BAE solution of Tim-Bor or 4% boric acid) on Streptomyces rimosus metabolites in preventing spore germination of sapstain and mold fungi using plate bioassay, Southern yellow pine and sweetgum block tests, and green pine log sections: sapstain -- Ceratocystis coerulescens, Ceratocystis minor, and Aureobasidum pullulans; mold fungi -- Aspergillus niger, Penicillium spp, and Trichoderma spp. Inhibition of spore germination in plate bioassay by metabolites with boron was more effective than without added boron. Treatment of wood samples with the mixture of boron and unconcentrated metabolites also resulted in the synergistic effect and completely inhibited spore germination of sapstain and mold fungi.
S C Croan, T L Highley


Insect resistance of preservative treated tropical plywood against Lyctus
1990 - IRG/WP 1453
Seven plywood types composed of tropical wood species, vulnerable to Lyctus, were treated with various commercial water-borne and oil-borne preservatives. A wide range of preservative retentions was obtained by treating boards with dip treatment, steeping, double-vacuum and vacuum-pressure impregnations. Selected samples were subsequently tested for their insect resistance against Lyctus africanus during 6 to 8 months according to European Standard EN 20. All control samples were attacked, except one Obeche plywood exhibiting only 50% attack. Water-borne preservative solutions containing arsenic, boron or fluoride could not prevent attack at common retention levels for interior use e.g. lower than 5 kg/m³. Quaternary ammonium compounds showed no insecticidal efficiency, up to 3 kg/m³. TCMTB at 1.5-1.7 kg/m³ proved to be able to reduce slightly the susceptibility for insect attack. Organic insecticides gave the best results, with nearly no attack for plywood treated with lindane or cypermethrin. In spite of a preservative uptake of 25 to 30 kg/m³, endosulfan only could reduce attack by 50%. Protection by permethrin at 0.1% a.i. required a retention of 28 kg/m³. Besides the fact that variability in wood species and composition of the plywood are leading to different retention levels, variation in penetration and distribution of a.i., and as a consequence to a different insect resistance of the impregnated boards, some poor results were directly related to inadequate insecticidal activity and/or concentration of a.i. in some commercial formulations for Lyctus control.
J Van Acker, M Stevens, M Pallaske


Non-pressure treatability of plywood by CCA, CCB and boron
2005 - IRG/WP 05-40295
Study on diffusibility and absorbability of CCA, CCB and boric acid in 3 mm thick 3-ply hardwood plywood at water saturated and air-dry conditions and dipped at same concentration (5%) and same duration of time (12 hours) revealed complete diffusion of all the preservatives at water saturated condition. Only the CCA-C was found absorbed by the plywood at air-dry condition. The rate of absorption and diffusion of CCA-C was found about 4.5 times higher than CCB and boric acid.
A K Lahiry


Leaching of the new boron based biocide from coated wood
2001 - IRG/WP 01-30267
We investigated leachability of the new boron based biocide - a complex of an amine and boric acid - from vacuum impregnated spruce wood samples. It was determined by the standard ENV 1250-2 procedure that the new biocide is susceptible to leaching so from the water borne as well as from the ethanol borne boron containing preservative treated wood. Leaching may be retarded by application of surface coatings. The ability of a surface finish to prevent leaching is correlated to its water vapour permeability.
M Petric, M Pavlic, F Cadez


CCA modifications and their effect on soft rot in hardwoods
1982 - IRG/WP 3201
Decay tests were carried out on wood samples treated with three waterborne compounds all identical in composition but applied in different forms. There were significant differences in the effectiveness of the treatments particularly as regards the control of soft rot.
S M Gray, D J Dickinson


Depletion of boron and copper from CCB treated test specimens using different leaching protocols
2004 - IRG/WP 04-50208
The objective of this study was to measure the depletion of inorganic wood preservative components regarding the proposed OECD guideline "Estimation of emissions from preservative-treated wood to the environment: laboratory method for wooden commodities exposed in the use class 4 and 5" as part of the project "Investigations concerning the influence of test parameters on the release of biocidal actives from treated timber in leaching tests". Pine sapwood specimens (50x10x150) were pressure impregnated with CCB according to European Use Class 4. Before leaching all samples were stores 4 weeks for fixation. In addition leaching tests were performed according to the European Standard EN 84 by means of EN 113 blocks. Parallel investigations were carried out between two laboratories to assess the repeatability and comparability of the methods. The results of chemical analysis of leachates taken at different time intervals show that similar depletion rates were determined for copper and boron independent on the leaching protocol used. However, the loss of copper as well as chromium in short term dipping experiments was often lower than the detection limit. Furthermore it can be stated that the difference between parallels was higher for the results which were obtained for the OECD guideline that EN 84. A comparison of both laboratory results indicate that a quite good repeatability is given in case of the CCB treated material.
E Melcher, R-D Peek, U Schoknecht, R Wegner


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


Water-based wood preservatives for curative treatement of insect-infested spruce constructions
1998 - IRG/WP 98-30171
On laying down sanitation measures for wooden constructions infested by wood boring insects, we must take into account static risks for the construction - and, thus, for the security of the user - as well as risks for humans and environment due to the chemical preservative compounds of the treated wood. Analyses on many roof constructions made with spruce (Picea abies L.) have revealed that Hylotrupes bajulus L. and Anobium punctatum De Geer have not the significance given to them for decennies. That often allows to replace solvant-based with water-based wood preservatives in old buildings, for the protection of humans and environment. Therefore, a method has been developed in Switzerland for testing wood preservatives with delayed curative efficacy against the house longhorn beetle. Like the European Anobium Standard EN 370 this method intends to prevent the emergence of Hylotrupes beetles. Laboratory tests with diverse water-based wood preservatives available on the market in Switzerland have shown that particularly boron and benzoylphenylurea derivatives containing products get a sufficient penetration in the wood and prevent the emergence of the beetles.
E Graf, P Manser, B Lanz


The long-term performance of boron treated joinery in service - A case study
2000 - IRG/WP 00-20208
Joinery treated with borates 23 years ago and in service in residential flats was surveyed and analysed for boron content. The levels of boron still present were sufficient to prevent decay. None of the windows surveyed showed any decay despite the fact that moisture and sapwood contents were conducive to decay.
D J Dickinson, R J Murphy


Boron treatments for the preservation of wood - A review of efficacy data for fungi and termites
1994 - IRG/WP 94-30037
Boron treatments have been used for many decades for protection of timber from biological attack and also as a fire retardant treatment. In recent years there has been an increased interest in boron treatments as an option for protection of structural timbers' e.g. timber framing used in termite risk areas. This paper reviews efficacy data for both fungi and termites relevant to this end-use.
J A Drysdale


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