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Adsorption of ACQ components in wood
2010 - IRG/WP 10-30522
To investigate the chemical adsorption capacity of copper-monoethanolamine (Cu-Mea) components on wood, the Na+ cation exchange capacity (CEC) of red pine (Pinus resinosa Ait.) was determined and compared to the adsorption capacity of free Mea and Cu-Mea complexes. The CEC increased with increasing pH. Free Mea adsorption as a function of pH followed the sodium adsorption curve except at pH over 9, when it exceeded the CEC. Cu-Mea adsorbed up to the CEC at pH 9.0-9.5 apparently as Cu(Mea)+, whereas the complex in solution is predominantly of the form Cu(Mea)2+. For the quaternary ammonium compound, alkyl dimethyl benzyl ammonium chloride (ADBAC) adsorption isotherm showed two different adsorption mechanisms into wood: ion exchange reaction at low concentration and hydrophobic interaction at high concentration. ADBAC adsorbed at solution concentrations below a critical concentration (hemi-micelle concentration) had high leaching resistance while ADBAC adsorbed into wood at above the critical micelle concentration (CMC) had low leaching resistance. The CMC decreased with addition of Mea and Cu-Mea. The anion, Cl- of ADBAC was only adsorbed at solution concentrations above the CMC and was easily leached out. The adsorption capacity of ADBAC into wood by cation exchange reaction did not achieve the cation exchange capacity (CEC) of wood. However, the total adsorption of ADBAC and Cu achieve the CEC of wood in the presence of copper amine, and ADBAC competes with copper to occupy the same sites in wood.
Myung Jae Lee, P Cooper

How to Document the Performance of Super-Critical Treated Wood in above Ground Situations?
2005 - IRG/WP 05-20316
The paper presents practical experiences from the preparation of a new preservative treated wood product for introduction to the market. The product in question is Superwood™, which is treated with organic biocides using CO2 in a supercritical state as a solvent. The question is how to evaluate the performance of a new product such as Superwood™ in order to get an acceptance on the market and fulfil the formal requirements. In the European Union countries, the EN 599-1 is the standard that needs to be complied when approving a new product for the market, but it only focuses on the toxic limit against representative decay fungi according to EN 113. However, decay test, above ground and other forms of field tests are optional, this is not in line with the traditional test philosophy in the Scandinavian countries. The open question is to which extent treatment to the level of the toxic threshold value also ensures a long service life and expected performance of the treated commodity. Superwood™ is evaluated using a strategy, in which basic laboratory tests are done to get the toxic value (according to EN 599-1) and in addition a number of field tests are done including accelerated testing in the tropics. These tests are focussed on the evaluation of the performance criteria such as durability and service life and maintenance requirements. These questions must be answered by the producer without having a full record of performance test for their new products. A short status on the test performed on super-critical treated wood (Superwood™) is presented. Based on a comparison between field test in Scandinavia and in the tropical Malaysia a service life of more than 25 years for a specific supercritical treated product is estimated. It is stated that the existing European standardisation system is insufficient when it comes to service life prediction. A number of important questions need to be addressed by the European standardisation system as soon as possible because the market and the public opinion change quickly due to environmental concern.
N Morsing, A H H Wong, F Imsgard, O Henriksen

Proposed methodology for the assessment of safety indexes
1990 - IRG/WP 3562
Safety Indexes (SI)s are developped on the same concept as Efficacy Indexes (EI)s: EIs are retentions of wood preservatives (percentages of the critical values "efficacy") which are presumed efficient for a given biological class of risk. In the same way, SIs are retentions of wood preservatives (percentages of the critical values "safety") which are taken as acceptable for human health and the general environment. EIs and SIs as well are derived from different types of bioassays and related to objectives of quality which may be either regulatory or harmonized within the programmes of the Standard Committees (CEN TC/38 for example). Critical Values are characteristics of wood preservatives; EIs and SIs are characteristics of treated wood; they vary with the different classes of risks.
G Ozanne

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

Wood preservation in France. "Bois plus" chain of quality. Description of the scheme early 1989
1989 - IRG/WP 3519
1989 - description of the French "CTB-BOIS PLUS" homologation scheme...
G Ozanne

A critical review of the AWPA standard method (M12-72) for laboratory evaluation to determine resistance to subterranean termites
1986 - IRG/WP 1298
The American Wood Preservers' Association standard (M12-72) for evaluation of candidate wood preservatives against subterranean termites is reviewed and suggestions for revision are made. The most serious flaws in the current test procedure involve a failure to recognize inter- and intraspecific variation and a lack of quantification of test results.
J P La Fage, M Jones

The effect of temperature on the rate of fixation of an alkyl ammonium compound (AAC) wood preservative
1984 - IRG/WP 3293
The rate of fixation of an alkyl ammonium compound wood preservative was measured by soaking samples of wood wool in various preparations of the preservative for arbitrary times followed by immediate leaching in water. The wood wool was then analysed for residual preservative. The results indicated that fixation was very rapid and increased at higher temperatures.
P Vinden

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

Factors affecting the sorption of preservative during diffusion treatment of wood
1988 - IRG/WP 3500
The sorption of preservative into wood during soaking in aqueous solution was found to comprise absorption as well as diffusion of solute. Absorption was increased by partially seasoning the wood prior to soaking and was characterised by (a) a very rapid initial rate of uptake and (b) an extended period of slow uptake, the rate of which varied with prior conditioning. It was concluded that some partial seasoning was desirable to optimise absorption (and therefore reduce soaking times), but that extensive partial seasoning would not significantly increase the quantity of solution taken up during short soaking periods, because of the back pressure from air which tended to become embellished in the wood during soaking. The factors influencing the retention of solute following momentary immersion were identified and included: 1. Surface roughness (which may be influenced by the basic density of the wood species together with the wood sawing or machining processes used); 2. The critical surface tension of the wood substrate; 3. The solubility of the solute; 4. The surface tension of the solution. It was found that during momentary immersion the surfaces of the wood become saturated very quickly. When stored overnight under non-drying conditions however, there was movement of the solution from the surface to the coarse capillary structure of the wood. Subsequent dipping in solution resaturated the surface of the wood. Thus by a process of multiple dipping preservative retentions could be increased as though timber had been kept in the solution.
P Vinden

Wood extractive concentration and sem examination of pretreated southern yellow pine wood chips with blue-stain fungi for mushroom production
2001 - IRG/WP 01-10407
Mushroom-producing white-rotting basidiomycetes either do not colonize or else colonize very poorly on freshly prepared southern yellow pine wood chips. This study evaluates the resinous extractive content of southern yellow pine before and after treatment with colorless mutant blue-stain fungi. The blue-stain fungi penetrate into the sapwood of southern yellow pine and utilize nonstructural resinous extractives, simultaneously reducing the total resinous extractive content. Scanning electron microscopic examination showed that heavy mycelial growth with good sporulation occurred on the surface of wood chips within 2 days and in parenchyma cells within 6 days. Ophiostoma spp. removed 61.1% to 99.9% of the extractives from the southern yellow pine wood within a period of 4 to 5 days. We conclude that white-rot basidiomycetes can easily colonize and produce fruiting bodies on treated southern yellow pine wood wastes.
S C Croan, J Haight

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

Health hazards and environmental aspects when using Cu-HDO-containing wood preservatives in vacuum pressure plants
1993 - IRG/WP 93-50001-11
Apart from the biological efficacy of wood preservatives, the health and environmental aspects concerning the utilisation of wood preservatives, the use of treated timber and the disposal of impregnated wood are of high significance today. Therefore, information on a possible aerial concentration of wood preservatives, on the mobility of active substances in soil leached from treated timber in service and on the composition and toxicity of thermal decomposition gases releasing on combustion of impregnated wood, are of absolutely fundamental interest. Measuring procedures relevant for the practical application will be presented, and the results concerning the utilisation of Cu-HDO-containing wood preservatives will be described. With the proper use of Cu-HDO-containing wood preservatives, the aerial concentration at workplace falls distinctly below the maximum permissible limit. If vacuum pressure treated timber is used properly, no active substances will seep into the ground water as a result of the leaching process of impregnated wood in service. The composition measured and the acute toxicity of the thermal decomposition gases released on combustion of impregnated wood may axtually be compared to those of untreated timber.
W Hettler, S Breyne, M Maier

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

The influence of gaseous oxygen concentration on fungal growth rates, biomass production and wood decay
1998 - IRG/WP 98-10283
The effects of air and several levels of oxygen balanced with nitrogen (% oxygen (v/v) nitrogen to 100%) on growth rates, biomass production and wood decay were investigated. The best technique for measuring daily growth rates in anaerobic jars was found to be by using 40 mm petri dishes which were attached to the walls of the jars. At the end of the test period the same petri dishes were also used for determining the dry weight of the fungal mycelia. The results showed that 5% oxygen concentration was very favourable for white rot and brown rot fungi (Basidiomycetes). When oxygen levels were reduced from 1% to 0.01%, the growth rates and dry weight of these fungi were steadily decreased. On the other hand, there was a large difference between very low oxygen levels (0.01 to 1%) and other levels (5 to 21% 02). In the case of other fungi there was not a big difference on their growth rates and biomass. Observational and numerical results on Fagus sylvatica (beech) and Pinus sylvestris (Scots pine) degradation by Coriolus versicolor, Coniophora puteana and Chaetomium globosum showed that there was a large difference in the degradation of the wood samples caused by C. puteana and C. versicolor when exposed to air and other levels of oxygen (0.25,1, 5 and 10% 02). Weight losses obtained by C. globosum as a soft rot on timber specimens in air and other oxygen levels were all in same range and below 5%. On the other hand there was a safety point at 5% 02 below which the fungus was unable to degrade beech. This point was 10% 02 for scots pine. At these points, weight losses were under 5%.
S M Kazemi, D J Dickinson, R J Murphy

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

Environmental risk assessment of treated timber in service: The Environment Focus Group approach
2000 - IRG/WP 00-50162
In the context of the Biocidal Products Directive (98/8/EC), and of the OECD work on wood preservatives, the Environment Focus Group (EFG), comprising 8 institutes and the European Wood Preservative Manufacturers Group, has been working on the environmental risk assessment of treated timber in service. A literature review of emissions from treated timber has revealed that very little existing data is usable for environmental risk assessment; the most relevant data are kinetic curves of emissions over time, which show clearly the non-linear emissions behaviour of treated wood over time. The EFG has suggested real exposure conditions for treated timber in the environment, and listed typical exposure scenarios. Five representative scenarios are characterised in detail, for use in the calculation of Predicted Environmental Concentrations (PECs). The existing methods to determine emissions from treated wood have been reviewed. Most existing experimental models cannot be used to predict environmental emissions. Monitoring of commodities in service has its specific constraints. Chemical analysis and ecotoxicity testing have also been reviewed and their relationship has been discussed. Principles for the design of experimental models, for the determination of emission fluxes from treated wood to the environment, have been established.
G Deroubaix, G Labat, I Le Bayon, S Legay, P Marchal, C Yrieix, E Melcher, R-D Peek, S De Geyter, J Van Acker, W J Homan, D J Dickinson, R J Murphy, E D Suttie, A J Nurmi, A-C Ritschkoff, D Rudolph, I Stephan, D Aston, E F Baines, J B Simonin

A comparison of inductively coupled plasma spectroscopy and neutron activity analysis for the determination of concentrations in wood
1993 - IRG/WP 93-10048
As wood decays the ionic composition changes, with increases often being seen in the concentrations of Ca, Mg, Fe, Mn and sometimes K. The concentration of eight cations in red spruce sapwood and heartwood samples was determined independently by inductively coupled plasma spectroscopy (ICP) and by neutron activation analysis (NAA) as part of an effort to standardize our analytical procedures and create a uniform wood standard for use by multiple researchers. Preliminary studies indicate a difference in the values of Ca and K as estimated by ICP and NAA, possibly due to a loss of these elements due to volatilization during ashing.
J Jellison, J Connolly, K C Smith, W T Shortle

Influence of concentration, catalyst, and temperature on dimensional stability of DMDHEU modified scots pine
1998 - IRG/WP 98-40119
Dimethyloldihydroxyethyleneurea (DMDHEU) is being used in textile industry to improve wrinkle recovery. Trials on solid wood have been performed to minimise swelling of the wood. This paper focuses on the effect of various types and concentrations of catalyst and reaction temperature on the dimensional stability of Scots pine. Three different catalysts, NKS (based on magnesium chloride), 3282 (based on aluminium chloride) and citric acid have been tried separately or in combination with tartaric acid. Reaction temperatures between 100° and 125°C have been investigated. The results showed that an anti shrink efficiency of up to 50% can be obtained.
M Van der Zee, E P J Beckers, H Militz

The critical moisture and temperature conditions for the growth of some mould fungi and the brown rot fungus Coniophora puteana on wood
1988 - IRG/WP 1369
The growth of some mould fungi on pine and spruce sapwood was studied in 40 different constant moisture and temperature conditions. The temperature range was between +10 and +40°C and the relative humidities varied from 76 to 100% relative humidity (RH). The incubation time was 12 weeks. The mixed mould inoculation used included typical fungi growing on wood: Aspergillus versicolor, Cladosporium sphaerospermum, Penicillium sp., Aureobasidium pullullans and other fungi, which were collected from the air in the Forest Products Laboratory. The growth of Coniophora puteana was studied at +20°C and the relative humidity range was between 76 and 100% and the incubation time 60 weeks. The studied moulds grew rapidly in higher humidities (RH > 96%). The lowest humidity for growth was 80%, where the growth was very slow and it could be detected only by microscopy. At higher temperatures the growth was faster and the needed relative humidity was lower than it was in lower temperatures. The brown rot fungus Coniophora puteana grew only at 96-100% RH conditions, where the moisture content of wood was over 25 weight%. The growth was very slow at 96% RH, and after one year incubation the weight losses were quite low. The mycelium strands could mainly be clearly detected, but in some cases no mycelium could be detected on the surface of wood, even if weight losses were measured.
H Viitanen, L Paajanen

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

The suitability of high pressure sap-displacement for the retention of UK grown spruce and pine
1990 - IRG/WP 3595
The concentration and radial distribution of copper, chrome, arsenic (CCA), and the moisture content and depth of radial checking in UK grown, field exposed spruce and pine poles treated by high pressure sap-displacement are examined. The concentration of CCA elements in samples obtained from increment cores is similar in Norway spruce, Scots pine and Corsican pine but is significantly lower in Sitka spruce. The concentration of chromium in all species, arsenic in Sitka spruce, Norway spruce and Corsican pine and copper in Sitka spruce are at a maximum in the outer sapwood and decrease centripetally with increasing core depth. In contrast, arsenic in Scots pine and Norway spruce at groundline and copper in Norway spruce, Scots pine and Corsican pine are at a maximum in the inner sapwood. The slopes of metal concentration against radial core depth are similar in Norway spruce and Scots pine but are significantly larger (steeper) and smaller (less steep) respectively in Sitka spruce and Corsican pine. Checking is more severe in Sitka spruce than in the other species and appears to be associated with steep moisture gradients. In Sitka spruce, checks penetrate the preservative treated annulus thus greatly facilitating decay since micro-organisms have access to untreated non durable wood. The results suggest that high pressure sap-displacement is suitable for the treatment and long term protection of Norway spruce, Scots pine, and Corsican pine but is inadequate for the protection of Sitka spruce. Modifications to the high pressure sap-displacement process that could improve the treatment of Sitka spruce are discussed.
P D Evans, S D Hainey, A Bruce, G M Smith, B King

Models of the critical time of humidity and temperature conditions for the development of mould fungi in pine and spruce sapwood
1995 - IRG/WP 95-20066
Regression models of the time factor for the growth of mould fungi in pine and spruce sapwood are studied. The first group of models are based on the results of exposures of mould fungi in static humidity and temperature conditions indicating the time for the start of mould growth in wood. The second group of models are based on the exposures of mould fungi in fluctuating or alternating humidity and temperature conditions when limited models are presented. An aspect of surface quality (nutrient rich, nutrient poor) and wood species (pine, spruce) are included in the models. The growth of mould fungi on wooden materials depends mainly on the water activity (the air relative humidity), temperature, exposure time, presence of mould fungi and other organisms and the nutrient content of wood surface. In humidity exposures at RH above 80% (water activity above 0,8) of several weeks - months, the risk for the mould growth in pine and spruce sapwood exists when the temperature is between +5 and +50°C. Between -5 and +5°C, the growth of mould fungi is slow and possible only when the water activity is above 0,9. At water activity above 0.95 (RH 95%), the critical time for mould growth in wood is only some days, when temperature is between +25 and +45°C, and some weeks, when temperature is between +10 and +20°C. Within the same temperature and humidity conditions, the critical time for mould growth on nutrient rich wood is shorter than that of wood with low nutrient content In fluctuating humidity conditions when favourable and unfavourable conditions are alternating, the development of mould fungi is slower and the final rate of mould growth is lower as compared to the constant favourable condition
H Viitanen

Effect of climate, species, preservative concentration and water repellent on leaching from CCA-treated lumber exposed above ground
2001 - IRG/WP 01-50178
Few studies have examined leaching of chromated copper arsenate (CCA) from treated wood in above ground exposures due to the assumption that leaching is less severe compared to wood in continuous contact with soil or water. However, a significant portion of CCA treated wood is used for above ground applications, exposing considerable volumes of the preservative to precipitation and potential leaching. This paper presents preliminary results of a one-year study that continuously monitors CCA leaching from above ground, naturally exposed 5.08 cm x 15.24 cm (2 x 6 inch) dimensional lumber. Three wood species, southern yellow pine (Pinus spp.), jack pine (Pinus banksiana Lamb.), and black spruce (Picea mariana (Mill.) B.S.P.), along with two preservative concentrations and one commercial water-repellent are evaluated for their effect on leaching rates. Preliminary leaching results indicate significant differences between wood species, treating solution concentrations, and the use of water repellent. In addition it appears that climatic variables affect elemental leaching of copper, chromium and arsenic differently. However, the exact effects of climatic variables are inconclusive at this time. Upon completion, this study will offer a substantial amount of leaching data to validate the findings of previous leaching tests, and provide insight into the leaching mechanism of CCA-treated lumber in above ground exposures.
J L Taylor, P A Cooper

The remaining concentration of inorganic wood preservative components in EN 252 stakes after ground contact
2000 - IRG/WP 00-50159
In order to determine the biological efficiency and the remaining concentration of different inorganic and organic active ingredients during service, EN 252 specimens were impregnated with 3 copper based wood preservatives. The stakes were installed in the test field of the DESOWAG GmbH, Rheinberg, for at least 7 years. At the end of the field test some of these stakes were divided into 10 uniform segments. Afterwards each segment was milled and mixed to guarantee a nearly homogenous sample. After further sample preparation like an acidic digestion the remaining concentration of the inorganic components copper, zinc, boron and fluoride were measured by means of AAS, ICP and an ion selective electrode. Concerning the remaining concentration the following ranking of the investigated active ingredients could be deduced: Cr (90%)> Zn (60%)> Cu (40-70%) >= F (40%) > B (concentration <10%). Furthermore the results show that the remaining content of copper differs depending on the wood preservative used. The lowest content was detected for the CCZnF-formulation, the highest for the copper-quat-preservative. Furthermore it is obvious that the rate of biological decay correspond well with the distribution of the wood preservative components in the segments.
E Melcher, H-W Wegen

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