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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


A case study on quality control on telephone poles as a cost saving tool in Tanzania
1987 - IRG/WP 3418
A sample of 28 CCA treated Eucalyptus poles from a lot of 2,000 poles awaiting delivery to the field, was studied to reveal the quality of treatment. Results showed a product of very poor quality. Average figures for penetration and retention were 8.4 mm and 2.2 kg/m³; these results are 66% and 91% below the required standards, respectively. Consequences of such results are estimated to amount to losses of billion of shillings.
K K Murira


CCA fixation experiments. Part 1
1989 - IRG/WP 3504
A method of squeezing solution from CCA treated wood that has not been dried at various times after treatment appears to be useful in following the fixation of CCA in wood. Experiments confirm that temperature governs the rate of fixation.
W S McNamara


Investigation of the fixation in wood of chromated zinc chloride and copperised chromated zinc chloride preservatives
1976 - IRG/WP 372
A biological method of evaluating the extent to which CZC and CCZC preparations are retained in wood in terms of the potential protection which they afford against destruction by Merulius lacrymans (dry rot) is given. CCZC is recommended for protection of wood under moderate leaching conditions, while the use of CZC under such conditions is not recommended.
V N Sozonova, D A Belenkov


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


Sludge formation in timber treatment with CCA preservatives. Origin and elimination
1984 - IRG/WP 3276
The exact distributions between lignin and holocellulose and retentions on wood of copper, chromium and arsenic as a function of various sets of conditions in a factorial experiment in which combinations of three temperatures of treatment, three CCA solution concentrations, four pH's of the initial CCA solution and two timber species, namely Pinus radiata and Eucalyptus grandis, are reported. Temperature and concentration appear to have an equally important effect on the preservative chemicals retentions and distribution in timber. pH, has also an effect but somewhat less marked than temperature and concentration, with the exception of the formation of sludges. Multivariable regression equations describing the amounts of Cu, Cr and As fixed on lignin and holocellulose for both pine and eucalyptus are also presented. The timber species treated also appears to have an important influence on the amounts of chemicals fixed and their distribution. Eucalyptus appears to be much less tolerant than pine to extremes of treating conditions. The influence of treating time under the most common treating conditions is also briefly discussed.
A Pizzi, W E Conradie, A Jansen


Practical consequences of the clarification of the chemical mechanism of CCA fixation to wood
1983 - IRG/WP 3220
Practical consequences derived from the chemical investigation of the mechanism of fixation of CCA to the wood constituents are discussed. Among these, formulas for the calculation of the time of hexavalent chrome fixation are presented. Furthermore, three parameters are shown to be important to the long-term effectiveness of CCA-treated timber: (i) the temperature of treatment, (ii) the initial pH of the CCA solution and (iii) its concentration. Variation in the values of these three parameters cause drastic differences in the distribution between lignin and holocellulose of the preservative chemicals which will considerably affect the durability of CCA-treated timber. New, more economical and more effective application schedules and CCA formulations both in chemical composition and requiring lower retentions (softwoods) and imparting equal or superior durability to the treated timber can be devised from the results presented. From the results it appears that CCA formulations producing better soft-rot resistant hardwoods can be devised and the changes necessary to obtain this, are outlined.
A Pizzi


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


Occupant re-entry times following insecticidal remedial treatments of timber in dwellings
1995 - IRG/WP 95-50055
This work was carried out principally to obtain quantitative data on the aerial concentrations of permethrin and white spirit likely to arise following the remedial treatment of timber in buildings, using insecticidal formulations. Such data are needed to allow assessments to be made of the length of time buildings should remain unoccupied following such treatments prior to re-occupation, and the likely levels of exposure of the occupants to the treatment products concerned. Two large, free-standing, wood-lined chambers were treated (in separate experiments) with a dilute oil-in-water emulsion and a micro-emulsion, both containing 0.2% m/m permethrin. The atmospheres in the chambers were sampled at intervals and analysed for their permethrin content. In addition, the aerial concentrations of white spirit were determined following treatment with the dilute oil-in-water emulsion. Results indicated that the aerial concentrations of permethrin following treatment never exceeded 20 µg/m³. Comparison of the measured levels with the threshold limit value (TLV) for permethrin (modified to a TLV/40 to represent the value associated with 24 hours-a-day continuous occupancy) indicated that such levels of permethrin constituted no significant risk to occupants. Aerial concentrations of white spirit in the test chambers from the dilute oil-in-water emulsion product indicated by calculation that the TLV/40 of this solvent would be attained approximately 10 hours after treatment in a model domestic situation having the relatively low air exchange rates of the test chambers. This work has shown the importance of further studies needed to identify the rate determining step in the evaporation of deposited constituents from the surface of timber and to quantify the effect of different air exchange rates in treated premises on the aerial levels of formulation constituents.
R J Orsler, G E Holland, G M F Van Eetvelde


Soil treatment tests with the three products of boric acid for the prevention of the hyphal growth of Serpula lacrymans
1992 - IRG/WP 92-3693
Laboratory soil treatment tests were conducted for the evaluation of fungicidal or fungistatic effect of boric acid products against Serpula lacrymans. Boric acid products tested were the following three: a thickened boric acid solution in triethanolamine, boric acid-silica gel complex granules, and a nonwoven fabric laminated with a polypropylene film and coated with boric acid granules on one side surface. Effects of these products were evaluated using ezomatsu (Picea jezoensis) wood blocks and Kanuma soil or unsterilized sandy loam as a soil substrate. The thickened boric acid solution exhibited the sufficient efficacy to suppress the hyphal growth and decay of wood with boric acid retention of 2.0 kg/m³ in Kanuma soil medium. The perfect effect of the boric acid-silica gel complex granules was shown with boric acid retention of 3.0 kg/m³. The hyphal growth of the fungus was almost inhibited by placing the nonwoven fabric with boric acid granules over the media incubated with the fungus.
S Doi, A Yamada, Y Mineki, M Mori


Moderate temperature fixation of CCA-C
1989 - IRG/WP 3522
Several Canadian treating plants are using moderate temperature (40-60C°) fixation chambers to reduce drippage and leaching from fresh CCA treated wood. In this study, chromium reduction and surface leaching properties of CCA-C treated red pine (Pinus resinosa) pole sections were monitored during exposure to temperatures of 50-60C° and 90-100% RH conditions. Chromium-VI concentration in the absorbed treating solution dropped significantly during the treating cycle to 50-60% of that in the free treating solution. The chromium-VI concentration also dropped with increasing depth in the pole. During the six to 24 hour fixation cycle the Cr-VI concentration dropped steadily especially in the outer layers of the pole, but even after 6 hours, a significant amount of Cr-VI was observed at all measured depths. After 12 hours, Cr-VI was only barely detectable at all depths. The leachate analyses were consistent with the Cr-VI results, indicating reduced but still significant surface losses while Cr-VI could still be detected.
P A Cooper, Y T Ung


Assessing health risks to occupants following remedial insecticidal treatment of timber in dwellings
1998 - IRG/WP 98-50101-27
Experiments have been carried out to assess (i) the aerial concentrations of volatile wood preservative constituents, and (ii) the potential for contamination from treated surfaces, following in situ insecticidal treatment of timbers in dwellings. Using white spirit as a model for volatile constituents in the treatment of free-standing, wood-lined chambers indicated that temperature and air exchange rate significantly affect the rate of decrease of aerial concentration, but that the rate of diffusion through the treated wood surface may be the ultimate rate-determining step. A simple mathematical model has been proposed to assist in calculating minimum re-entry times after treatment associated with different wood preservative constituents. Using lindane as a model compound in different solvent formulations, comparison between measurements of the concentration at the surface of the treated wood and pick-up by direct contact has demonstrated the need for an agreed methodology for assessing risk through contamination from treated surfaces. Both methods demonstrated that the amount of lindane close to or at the surface of the treated wood decreased with time, thus reducing potential for pick-up.
R J Orsler, E D Suttie, V Rijckaert


Tilting and vacuum treatment - two methods to obtain a non-dripping freshly treated timber
1989 - IRG/WP 3535
Modern impregnation plants are designed to prevent spread of impregnation solutions from the plant through leakage, etc. It is also important that freshly treated timber does not spread solutions through dripping on the storage area. To prevent this, the impregnation procedure is terminated with a vacuum period. In many plants in Sweden this period is minimized or even excluded to gain time. Instead the freshly treated timber is tilted for some time before it is transported to the storage area. To evaluate the effect of these two methods to get a non-dripping freshly treated timber a small study was carried out by the Swedish National Testing Institute (SP) together with the Swedish Wood Preservation Institute (SWPI).
I Johansson, M-L Edlund


Thickened boron treatment
1990 - IRG/WP 3632
Commercial trials with thickened boron preservatives "Diffusol™" indicate a number of advantages when compared to traditional methods of dip-boron preservative treatment. These include: (i) more even uptake and distribution of preservative on and within the timber; (ii) faster diffusion times; (iii) the treatment of gauged timber (though improved retention); (iv) saving in energy costs (heating of boron solutions no longer necessary and no burner maintenance); (v) improved sapstain and mould control during diffusion storage; (vi) the treatment of surface dry timber - overcoming the hydrophobic properties of surface dry timber; (vii) antisapstain formulated at time of manufacture - improved quality control and effectiveness; (viii) delivered as liquid - no bags to dispose of, no dust generated from emptying bags; (ix) reduced antisaptain chemical breakdown as solution is used at ambient temperature; (x) assistance in the treatment of high resin content species e.g., Pinus elliottii; (xi) reduced solution degradation (from wood sap diffusing into the solution); (xii) reduced aerosol effect during stacking; (xiii) cheaper manufacture - there is no costly flashing-off of moisture to produce powder boron preservatives. Forty timber preservation plants in New Zealand have adopted "Diffusol" in the first year of commercialisation.
P Vinden, J A Drysdale, M Spence


Experimental variations in the distribution of CCA preservative in lignin and holocellulose as a function of treating conditions (temperature, concentration, pH, species, and time)
1984 - IRG/WP 3277
The exact distributions between lignin and holocellulose and retentions on wood of copper, chromium and arsenic as a function of various sets of conditions in a 3x3x4x2 factorial experiment in which combinations of three temperatures of treatment, three CCA solution concentrations, four pH's of the initial CCA solution and two timber species, namely Pinus radiata and Eucalyptus grandis, are reported. Temperature and concentration appear to have equally important effect on the preservative chemicals retentions and distribution in timber. pH, has also an effect but somewhat less marked than temperature and concentration, with the exception of the formation of sludges. Multivariable regression equations describing the amounts of Cu, Cr and As fixed on lignin and holocellulose for both pine and eucalyptus are also presented. The timber species treated also appears to have an important influence on the amounts of chemicals fixed and their distribution. Eucalyptus appears to be much less tolerant than pine to extremes of treating conditions. The influence of treating time under the most common treating conditions is also briefly presented.
A Pizzi, E Orovan, M Singmin, A Jansen, M C Vogel


Effects of the sulfuric acid modification of CCA treating solution
1987 - IRG/WP 3415
Sulfuric acid modification of CCA treating solution is often used to control the formation of sludges and undesirable deposits on the surface of treated wood. The consequences of sulfuric acid addition are examined in this work and negative effects are shown to far outweigh any benefits. Major risks include the loss of copper due to leaching from treated wood and the accelerated corrosion of treating equipment when even small quantities of sulfuric acid are employed. Twenty-year stake test results demonstrate that the addition of as little as 0.5% by weight of sulfuric acid to CCA treating solution can result in premature field failure. A mechanism for the effects of sulfuric acid on the chemistry of this system is discussed.
R F Fox, H J Fry, E A Pasek, A S Ross


Effects of concentration and temperature of CCA and CCB on wood strength of Turkish fir (Abies bornmulleriana Mattf.)
2009 - IRG/WP 09-40450
The purpose of this study was to present evidence for the effects of concentration and temperature of solutions of water-borne preservatives (chromated copper arsenate, CCA and chromated copper boron, CCB) on the static bending properties (modulus of elasticity, MOE and modulus of rupture, MOR) of Turkish fir (Abies bornmulleriana Mattf.). Wood samples were mechanically tested after a mild full cell preservative treatment with 2.5 and 3.0% CCA and CCB solutions heated to 30 and 40 °C.Untreated controls were included for comparison.The experimental data indicated that heating the solutions of both CCA and CCB caused a greater shift in the fluid uptake, i.e. it increased with temperature up to 30 ºC, but at 40 ºC it was lower than that of unheated controls. In absolute terms, the fluid uptake of either preservative solutions was higher particularly in lower concentrations. CCB treatment had a greater fluid uptake for all cases. Results also showed that the effects of increasing concentration and temperature of both water-borne preservatives on MOE and MOR were very highly significant, while these strength properties were a significantly lower after the wood treatment with concentration of 3.0 % and heated at 40 ºC. Both MOE and MOR decreased even more by the treatment of CCB. It was therefore concluded that the strength properties of Turkish fir based on MOE and MOR were affected to a small extent by the full-cell vacuum/pressure wood treatment by using CCA and CCB with the concentrations of 2.5 and 3.0 % heated at 30 and 40 ºC. The worst case was 3.0% CCB treatment at 40 °C which resulted in a 5.0% reduction in MOE and a 5.2% reduction in MOR.
I Usta, M Hale


Preservative Treatment of simul (Bombax ceiba) Veneers with Hot and Cold Water Solution of borax-boric acid by Soaking Process
2010 - IRG/WP 10-40528
Veneers of simul (Bombax ceiba) were treated with different concentrations of water- borne preservatives borax-boric acid (BB) by soaking process for different time periods. In the case of hot water treatment, it was found that the average retention of preservative chemicals increased gradually with the increasing treatment period from 20 minutes to 60 minutes. Similar trend was observed in the case of cold water treatment when treatment period was increased from 1 day to 3 days. The maximum retention (20.37 kg/m3) was observed from the samples treated with 10% BB solution for 60 minutes and in 2.5% BB treated samples, the average retention gradually increased from 5.35 kg/m3 to 7.16 kg/m3 when treatment duration was varied from 20 to 60 minutes. In the case of cold water treatment, maximum retention (22.97kg/m3) was observed from the veneers treated with 10% BB solution for 3 days and 7.35 kg/m3 retention was obtained when treated with 2.5% Borax-boric acid solution for 1 day. According to the Indian Standard (IS-1902), the retention of 4 kg/m3 boron compounds are sufficient to offer protection for non-structural purposes.
K Akhter, Md Abul Hashem, S Akhter


Study on the Effect of Combined Nanosilver-Hygrothermal Treatment on Wood Properties
2012 - IRG/WP 12-40581
In this study, the impregnation process with nanosilver solution, before hygrothermal treatment was carried out to investigate its effect on some physical and mechanical properties of Iranian beech (Fagus orientalis Lipsky) and Russian imported spruce (Picea abies). Wood specimens were impregnated with nanosilver solution (400ppm) in an impregnation tank under pressure of 0.25 Mpa, for 20 minutes. Hygrothermal treatment was carried out at the temperatures of 120, 150 and 180ºC for 1, 3 and hours. One group of specimens was only hygrothermally treated and considered as controls. Values of volumetric swelling after 24 hours soaking in water, bending strength, impact load resistance and compressive strength parallel to the grain were measured. The results showed that by increasing the temperature of hygrothermal treatment volumetric swelling and mechanical properties of specimens were decreased. The duration of treatment has no significant effects on mechanical properties. Also, in wood specimens which were impregnated with nanosilver solution and treated at 180ºC, volumetric swelling were lower than controls, without any significant decrease in mechanical properties. On the whole, it could be said that with nano silver impregnation of wood, hygrothermal treatment can be carried out at higher temperature (180ºC) to achieve better dimensional stability with no more decrease in mechanical properties.
G Rassam, H Reza Taghiyari, A Karimi, B Jamnani, M Ebrahimi


Environmental safeness of 60% and 72% concentrated CCA-C solution and paste for wood treatment
2012 - IRG/WP 12-50284
In this study 30-years practical and observational experience of the present author about using of 72% concentrated CCA-C paste for preparing treating solutions and for treating wooden poles, anchor logs and cross arms has revealed that the 60% concentrated CCA-C solution is superior to the 72% concentrated CCA-C paste regarding solubility, homogeneity, cleanliness, treatability, sludge formation, problems of plant operators. Often certain percentage (1% to 2%) of 72% concentrated CCA-C paste cannot be dissolved in water and remain in solution as suspended minute particles that helps formation of sludge on treated products and at the bottom layer of reserve tanks. Therefore, 60% concentrated CCA-C solution has been found to be environmentally and economically safer than 72% concentrated CCA-C paste and has been recommended to use 50% to 60% concentrated CCA-C solution stopping using problematic 72% concentrated CCA-C paste as a source of treating solution.
A K Lahiry


Study on the Effect of Combined Nanosilver-Hygrothermal Treatment on Wood Properties
2012 - IRG/WP 12-40581
In this study, the impregnation process with nanosilver solution, before hygrothermal treatment was carried out to investigate its effect on some physical and mechanical properties of Iranian beech (Fagus orientalis Lipsky) and imported Russian spruce (Picea abies). Wood specimens were impregnated with nanosilver solution (400ppm) in an impregnation tank under pressure of 0.25 Mpa, for 20 minutes. Hygrothermal treatment was carried out at the temperatures of 120, 150 and 180ºC for 1, 3 and 5 hours. One group of specimens was only hygrothermally treated and considered as controls. Values of volumetric swelling after 24 hours soaking in water, bending strength, impact load resistance and compressive strength parallel to the grain were measured. The results showed that by increasing of the hygrothermal treatment temperature, volumetric swelling and mechanical properties of specimens were decreased. The duration of treatment had no significant effect on mechanical properties. Also, in wood specimens which were impregnated with nanosilver solution and treated at 180ºC, volumetric swelling were lower than controls, without any significant decrease in mechanical properties. On the whole, it could be said with nano silver impregnation of wood, hygrothermal treatment can be carried out at higher temperature (180ºC) to achieve better dimensional stability with no more decrease in mechanical properties.
G Rassam, H Reza Taghiyari, A Karimi, B Jamnani, M Ebrahimi


Overview of the treated wood quality control program in the United States with the recent challenges and advances
2017 - IRG/WP 17-20616
In the past two decades, there have been significant and rapid changes in wood protection technologies for residential applications which have moved away from long established heavy duty metal oxide based products such as chromated copper arsenate (CCA). The successor generation of wood protection systems usually contain copper as the primary biocide, in combination with carbon-based co-biocides such as quaternary ammonium compounds (Quat), and/or triazoles (Tebuconazole and/or Propiconazole). The most recent developments have given rise to even more complicated combinations including multiple carbon-based biocides formulated in the form of emulsions or dispersions with or without water repellents or polymers aiming to minimize the use of heavy metals as well as provide improvement in wood dimensional stability and surface weathering performance. Also, long developed non-biocidal wood modification treatments, such as acetylation, thermal modification, furfurylation and hydrocarbon wax/oil treated wood have finally gained more commercial traction in the market place, especially in Europe. These new developments have challenged the industry to develop and use appropriate methods in order to meet the quality control (QC) standards and requirements in respect to concentration of treatment solutions, as well as chemical retention and penetration in treated wood. In the US, the QC system for treated wood product includes three key elements: treating plant internal QC for treating solution, treated wood, and treatment process; QC assistance and monitoring by the chemical/technological suppliers for their customers, and QC inspection by third-party inspection agencies. The enforcement of the QC standards through this comprehensive system is essential to ensure the performance of the treated wood products, the validity of product warranty program, and ultimately for the protection of consumers and the public. This paper overviews the US’s current QC standards and procedures used by treating plants, suppliers and independent inspection agencies. The chemistry challenges with the recent developments of multi-component systems and complex wood protection technologies, and their impacts on quality control methods are also discussed. Case studies have been used to illustrate how some of these challenges can and have been successfully addressed.
L Jin


Proposal for further work on accelerated ageing
1988 - IRG/WP 2314
M-L Edlund


Status of the research and development of a new preservative system (EFPL) for pressure treatment of spruce in Canada
1975 - IRG/WP 348
Our work has been to develop a system which would have the stability of the ACA system and the formulation flexibility of the CCA system enabling properties such as fixation of arsenic, water repellency, appearance and cost to be controlled. Our permeability studies of spruce using a method previously developed indicated that an ammoniacal solution of copper arsenate is an excellent candidate for the treatment of spruce. Studies of the permeability of spruce sapwood microsections to CCA preservative and to an ammoniacal solution of copper arsenate proved that the ammoniacal system penetrates 1.7 to 1.8 times faster than the CCA system, in the radial direction. The permeability in the tangential direction was on the average 3.8 times better. These results were confirmed by pressure treatments of spruce lumber and spruce roundwood with both preservatives.
J Rak, M R Clarke


IRG/COIPM INTERNATIONAL MARINE TEST - to determine the effect of timber substrate on the effectiveness of water-borne salt preservatives in sea-water. Progress Report 2: Report of treatment and installation in Australia
1978 - IRG/WP 440
The purpose of this test and the procedures to be followed have been fully set out in documents distributed by the International Research Group on Wood Preservation and numbered IRG/WP/414 and IRG/WP/420. The prescriptions set out in these two documents have been closely followed.
J Beesley


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