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Treating Eucalyptus tereticornis wood with boron: Optimizing treatment conditions
2005 - IRG/WP 05-40309
Even though Eucalyptus tereticornis wood is suitable for small timber purposes, being non-durable, it needs to be treated with preservative chemicals. As it is a heavy, hard and difficult to treat species, the possibility of using diffusible boron compounds was investigated. The present study explored the effect of impregnation conditions such as treatment schedule, concentration of treatment solution and the moisture content of wood on the achievement of desired dry salt retention (DSR) of the preservative in the treated wood by conducting a commercial scale trial. The study revealed that wood density and moisture content adversely affected the boron impregnation. It was clear that even E. tereticornis wood in green condition could be effectively boron impregnated using appropriate treatment schedule. Only long duration treatment schedules were found to yield the desired DSR levels. A solution concentration of 8% boric acid equivalent (BAE) was found to be required. Application of an initial vacuum of 760 mm Hg (- 85 kPa) for 15 minutes followed by a pressure of 1300 kPa for a minimum period of 60 minutes and a final vacuum of 760 mm Hg(- 85 kPa) for 5 minutes was found to be an appropriate treatment schedule.
T K Dhamodaran, R Gnanaharan


Boron treatment methods for lyctid susceptible hardwoods growing in Tasmania
1998 - IRG/WP 98-30168
A survey of existing boron plants that treat to protect hardwoods from attack by lyctids in Australia showed that hot and cold bath, and vacuum pressure impregnation (vpi), were the two most common methods employed. In experimental work, two of the treatment methods, vpi and dip diffusion, were used to treat seasoned and green messmate (Eucalyptus obliqua) and blackwood (Acacia melanoxylon). The treating solution in both cases was Diffusol. For vpi treatment, a solution of 2.5% boric acid equivalent (BAE) was used to treat rough sawn boards with a Bethell schedule. After treatment, boards were strip stacked on a pallet under cover, later cut in half, and the centres sprayed with turmeric reagent to reveal that all sapwood was adequately treated with boron. The solution for dip diffusion contained 12% BAE. Block stacked timber was dipped, wrapped, and stored to allow diffusion of the boron. All green E. obliqua and A. melanoxylon boards were adequately treated after dipping in Diffusol and two, four or six weeks diffusion. Some of the air dried A. melanoxylon boards could not be adequately treated by this method when diffusion periods were just two or four weeks. However, a six week diffusion period allowed full sapwood treatment of all boards.
L J Cookson, D Scown, K McCarthy


Gaseous preservative treatment of wood
1990 - IRG/WP 3631
A recent development in processing wood with a gaseous preservative means that dry, treated wood can be produced in under 30 hours with the benefits of product diversification, faster stock turnover and the ability to respond to short term demand. About 400,000 m³ of wood are treated each year in New Zealand with boron salts to protect from borer infestation. Traditionally this treatment is effected by dipping the freshly sawn wood into a solution of boron salts and then stacking the wood while the salts diffuse through it. For 50 mm thick timber the diffusion process takes from 5 to 8 weeks. The Forest Research Institute has developed a new technique whereby the treatment is carried out in the gas phase effecting full impregnation within seconds. This process is carried out in a pressure vessel, which acts as both a kiln, preservation vessel and steam conditioning chamber. The wood is first high temperature dried to a low moisture content, exposed to a vapourised organoborate and then steamed. Total time in the vessel is about 30 hours. Preservative treatment in the gas phase is a novel development for the wood processing industry. An outline of the development of the process is presented and the implications for this industry are discussed.
R Burton, A J Bergervoet, K Nasheri, P Vinden, D R Page


The Effects of Industrial-Scale Heat Treatment and Impregnation with Boron Compounds on Water Uptake and Tangential Swelling of Some Wood Species
2012 - IRG/WP 12-40599
This study evaluated the effects of boron impregnation and heat treatment on water uptake and tangential swelling of spruce (Picea orientalis), pine (Pinus nigra), beech (Fagus orientalis) and poplar (Populus deltoides) wood species. The samples (10 x 5 x 40 - tangential x radial x longitudinal cm) were impregnated with 4 % boric acid and 4 % borax according to the ASTM D-1413 standard method. After the impregnation, heat treatment was applied on the impregnated test samples in an industrial plant, at four different temperatures and two different durations under steam atmosphere. Soft wood and hard wood samples were subjected to the heat treatment at 212 °C - 220 °C, and at 180 °C - 190 °C, respectively, for 90 and 120 min. Heat treated and impregnated test samples were reduced smaller sizes (3 x 3 x 1.5 cm - tangential x radial x longitudinal) for water uptake and tangential swelling tests. The tests were carried out based on TS 2472. Results indicated that the highest retension was 26.9 kg/m3 in pine wood samples impregnated with BA (26.93 kg/m3). Hardwood retention was lower than soft wood retention. In generally, water uptake and tangential swelling ratios of only heated samples was found lower than non-treated control samples.The combination of heat treatment and BX impregnation was negatively affected water uptake especially in spruce and poplar wood. Borax was more hygroscopic than boric acid. The tangential swelling rates of four wood species impregnated with boric acid and borax were found lower than the non-treated control samples. The tangential swelling rates of spruce and pine wood samples impregnated with boric acid decreased compared to the only heated samples. Heat treatment process significantly affected the remaining boron compounds in wood. Although the steam atmosphere in the oven during the heat treatment, the amount of boron leached from wood was low especially in BX treatment.
A Can, S Yildiz, Ü C Yildiz


Development of new wood treatments combining boron impregnation and thermo modification - Effect on decay and termites durability
2014 - IRG/WP 14-40666
Environmental pressures appeared in most European countries during the last decade has lead to the development of more environmentally acceptable preservation methods. In this context, wood heat treatment has been one of the most investigated alternative methods during the last years. Treated at temperatures ranging between 180 and 220°C, wood components undergo more or less important chemical modifications conferring to the material new properties like increased decay resistance or higher dimensional stability. However, even if some of the wood properties are improved, the overall durability of the material is not sufficient to envisage use class 4 applications, where the wood is in direct contact with soil. Impregnation of borax before thermal treatment could be an attractive way to improve properties of thermally modified wood. Indeed, boron is known as biocide allowing not only improving decay durability but also resistance to insects like termites. The main drawback of boron is its poor retention in wood due to its high leachability with water. To reduce boron leachability, polyglycerol methacrylate was added to the borax solution taking advantage of thermal treatment to initiate polymerization within the wood structure in order to limit boron mobility. Samples were the subjected to leaching before evaluation of their durability using different white rot and brown rot fungi. Results indicated a significant improvement of wood durability of treated samples even after leaching. Such treatments may be valuable alternative to extend the scope of utilization of thermally modified wood in outdoor conditions.
S Salman, A Pétrissans, M-F Thévenon, S Dumarçay, B Pollier, P Gérardin


Improvement of wood decay and termite durability resulting from combined treatments based on borax/phenol-formaldehyde impregnation followed by thermal modification
2019 - IRG/WP 19-40871
This study determined the factors influencing the boron content after leaching of pine blocks impregnated with aqueous solution of phenol-formaldehyde (PF) resin with or without borax and subjected to heat treatment by response surface methodology. An experimental design permits to analyze the effects of heat treatment temperature (150, 185 and 220°C), curing time (5, 12, 5 and 20 hours), resin concentration (5, 12.5, and 20%) and boron concentration BAE (0, 2, and 4 %) on the mass gain, boron content as well as degradability. After leaching, the treated samples with 20% PF, and 220°C had high boron content, and the heating time had no significant influence on the boron content. Decay and termite resistance were also studied for treatments involving impregnation of samples with 10% of PF alone or in the presence of borax, followed by curing at 220°C for 5 h. The results of this study indicated that the decay and termite resistance of all samples pretreated and leached is sufficient to envisage use in outdoor exposure.
S Salman, M-F Thevenon, A Petrissans, S Dumarcay, P Gerardin


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


Improved equipment and technique for high pressure sap displacement impregnation of natural round wood
1972 - IRG/WP 309
Hitherto the main problem in the practical application of high pressure sap displacement impregnation (HPSD) has been in devising a satisfactory cap. Such a cap must be easily fitted to different size log ends to give a leak proof seal. The present contribution describes a new type of cap and sealing system designed to meet these requirements.
C G W Mason, F B Shorland


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


An investigation of the effects of pre-steaming on the treatment of sawn spruce timber with Celcure A, a copper-chrome-arsenic preservative
1981 - IRG/WP 3150
Difficulties in the treatment of spruce using standard vacuum/pressure techniques with both water-borne and organic solvent preservatives are well known. We have evaluated the influence of steaming on treatability with a waterborne CCA preservative.
C R Coggins


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


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


Finite element analysis of boron diffusion in wooden poles
2003 - IRG/WP 03-40263
The problem of describing the migration of dissolved boron in wood is treated with special reference to the commonly used remedial treatment of wooden poles. The governing equations are derived and discussed together with some of the material parameters required. The equations are solved by the finite element method and finally, results showing the effect of different treatment strategies are presented.
K Krabbenhøft, P Hoffmeyer, C G Bechgaard, L Damkilde


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


Fire resistance of Alder wood treated with some chemicals. Part II. Effect of Other Chemicals on the Combustion Properties
2002 - IRG/WP 02-40235
Samples from alder wood (Alnus glutinosa (L.) Gaertn. subsp. barbata (C.A.Mey) Yalt.) were impregnated according to ASTM D 1413-88 with boron compounds (boric acid, borax, sodium perborate), vinyl monomers (styrene, methyl methacrylate), Tanalith-CBC, Phosphoric acid, Vacsol, Immersol, Polyethylene glycole (PEG-400) and their mixed solutions of chemicals in order to determine their combustion properties. The results indicated that inorganic boron compounds with aqueous solutions were very effective as fire retardant and reduced burning of some vinyl monomers at some extent such as styrene and methylmetacrylate when used as a secondary treatment chemical polimerized later on wood structure and phosphoric acid was also showed fire-reterdancy. Further studies are suggested on boron-vinyl monomers, and boric acid+borax with different concentrations by physical and chemical interactions in terms of fire reterdancy.
A Temiz, Ü C Yildiz


A new approach to the maintenance of wooden railway sleepers. (Second report)
1988 - IRG/WP 3492
The microenvironment and micro-ecology of wooden railway sleepers was investigated to assess their condition to determine the necessary treatment, repair and replacement criteria. In this report the efficacy of the secondary preservative treatment with solid boron rods is discussed and the development of an in-situ, nondestructive test method based on the creation and assessment of structural dynamic vibrations is described.
W Beauford, P I Morris, A M Brown, D J Dickinson


The benefits to New Zealand of boron salt treatment of Pinus radiata
1992 - IRG/WP 92-3692
The historical reasons for New Zealand adopting boric salt diffusion of Pinus radiata are summarised, and present day processes and their associated costs are given. The biological hazards of using Pinus radiata untreated are then argued, using endemic fungal and insect species as examples, as well as a discussion of the risks from species that may yet be accidentally introduced into the country.
D J Cross


HCB - a new preservative combination for wood pole maintenance
1996 - IRG/WP 96-30122
New combination of heavy creosoted boron (HCB) applied on hardwood and softwood logs at different moisture content revealed successful diffusion of boron in all sapwoods within 7 days and in all sapwoods plus hardwoods within 15 days. The new cost effective paste sterilizes wood through diffusion and suitable for pole maintenance at groundline and above groundline e.g. cut ends, drilled holes, woodpecker's holes etc.
A K Lahiry


The secondary treatment of creosoted electricity poles with fused boron rods
1988 - IRG/WP 3485
After preliminary trials selected poles were treated at the groundline with fused boron rods. Early samplings showed that movement was slow in the dry heartwood but after six years the distributions obtained indicate that the system has merit for the treatment of the heartwood of poles in service.
D J Dickinson, P I Morris, B Calver


Treatment of Douglas fir heartwood with disodium octaborate tetrahydrate (Tim-BorÒ ) to prevent attack by the Formosan subterranean termite
1991 - IRG/WP 1487
Toxicity of disodium octaborate tetrahydrate (Tim-BorÒ) to Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), and termite feeding on treated Douglas-fir heartwood were evaluated in laboratory and field tests. Feeding on filter papers impregnated with Tim-BorÒ solutions reduced but did not eliminate termite gut protozoan populations. In a forced-feeding laboratory assay, Douglas-fir heartwood treated to Tim-BorÒ retentions ³0.35% BAE drastically reduced termite feeding and resulted in 100% termite mortality within three weeks. Gradual and significant mortality (49%) after four weeks of feeding at 0.16% BAE suggests that this or lesser concentrations may be useful in baits for remedial termite control. After 162 days of field exposure to an active Coptotermes formosanus colony in an accelerated field test, moderate feeding was noted at 0.65% BAE (13.6% weight loss) and 0.73% BAE (16.9% wt. loss), and only slight damage (2.5% wt. loss) at the highest retention field tested of 1.02% BAE. These results indicate that Tim-BorÒ provides protection from Formosan termite attack, but that some cosmetic damage occurs even at high retentions. This cosmetic damage is unlikely to create a structural hazard, but additional field evaluations are needed to determine the treatment requirements for timbers visible to the consumer.
M Tamashiro, R T Yamamoto, J K Grace


Assessment of contamination of soil and water at a CCA treatment plant: A demonstration project
1996 - IRG/WP 96-50067
Soil, sludge, dust and water samples were collected at a copper/chromium/arsenic wood preservation plant. Contamination of soil, sludge, dust and surface water with copper, chromium and arsenic was detected. Levels of contamination were sufficiently high to require remediation. Contamination originated from preservative solution dripping from recently treated wood. Migration of contaminants was via surface water run-off; poor housekeeping and operational procedures; forklift movements and wind-blown dust.
P N Durrant, D C R Sinclair, G M Smith


Evaluation of a solid remedial wood preservative containing boron and fluorine
1993 - IRG/WP 93-30022
The fungicidal and termiticidal effectiveness of a new rod form of diffusible remedial wood preservative, containing disodium octaborate tetrahydrate/sodium fluoride and marketed as Polesaver Rod, was evaluated in laboratory tests against three species of basidiomycete fungi (Coniophora olivacea, Pycnoporus coccineus, Perenniporia tephropora) and two species of subterranean termites (Coptotermes acinaciformis, Mastotermes darwiniensis). The rods were dissolved in water and various dilutions were used to treat specimens of Eucalyptus regnans sapwood using a full-cell process, providing retention levels which ranged from 1.2 to 37.4 kg/m³. Soil jar decay tests have shown the remedial preservative is toxic to Coniophora olivacea and Pycnoporus coccineus at a retention of 1.2 kg/m³ solubilised total rod and 2.3 kg/m³ for Perenniporia tephropora. Mean% mass loss data showed that a retention between 2.3 and 4.7 kg/m³ was necessary to protect specimens from significant attack by Coptotermes acinaciformis and between 9.3 and 18.7 kg/m³ for the more voracious Mastotermes darwiniensis. Laboratory diffusion tests on several species of eucalypt hardwoods have confirmed the capability of the preservative's active ingredients to diffuse through both heartwood and sapwood in concentrations toxic enough to inhibit fungal growth. In addition, field testing has shown that after eight months, significant radial and longitudinal diffusion of boron and fluorine was achieved from rods introduced into Eucalyptus obliqua pole stubs. Samples taken within the diffusion zone indicated loadings of up to 4.1 kg/m³ of boron and 5.2 kg/m³ of fluoride.
K J McCarthy, J W Creffield, L J Cookson, H Greaves


Study on the treatment of construction timbers by diffusion methods
1983 - IRG/WP 3252
Several species of timber that could be used for constructional purposes have to be pressure impregnated before such use. Pressure impregnation requires expensive equipment, and needs specialized trained operators, etc, which is not possible in most parts of India. Some timbers cannot be pressure impregnated, but can be treated by diffusion. Diffusion treatments could protect these timbers with simple inexpensive apparatus, using local resources and labour. It is our purpose, therefore, to locate such species which are commonly used in India for constructional purposes, and to preserve these by diffusion; to check if the results are satisfactory, and to find a preservative and simple procedure for the treatments of these timbers based on their treatability.
V R Sonti, B Chatterjee


Washboard effect: A surface deformation of spruce resulting from vacuum-pressure impregnation with water-borne preservatives
1987 - IRG/WP 3450
The washboard effect has been observed in sawn spruce after both commercial and laboratory based preservative treatments and is of increasing economic importance. The effect is defined as a specific phenomenon at the wood surface. It is distinct from internal collapse in the wood, but it may occur in association with internal collapse damage. Experimental investigations on the causes of washboarding and preliminary results indicate that a combination of several factors induce the effect. At treating pressures below about 10 bar washboarding appears to develop with post treatment drying of the wood whereas with higher pressures it will occur during the impregnation cycle. Further research has been started to develop measures to minimise the problem.
H Willeitner, R J Murphy


Ancillary properties of vapor boron-treated composites
2001 - IRG/WP 01-40210
This paper discusses the water absorption, thickness swelling, and internal bond strength of North American composites treated using a vapor boron treatment process. For oriented strandboard, high boron loadings led to lower internal bond strength and lower thickness swelling. Water absorption results were variable but no deleterious effect of treatment was noted. For medium density fiberboard, the highest loadings led to reduced internal bond strength. Thickness swelling decreased with increasing boron level, but not significantly. As with OSB, water absorption results varied.
W A Jones, H M Barnes, R J Murphy


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