Your search resulted in 172 documents. Displaying 25 entries per page.
Application of radio frequency heating to accelerate fixation of CCA in treated round-wood
1999 - IRG/WP 99-40133
The potential of radio frequency heating to accelerate the fixation of chromated copper arsenate (CCA) in treated round-wood was assessed. Pre-dried Douglas-fir and western red cedar round-wood sections were pressure treated with CCA in a pilot plant retort, after which they were placed individually in a pilot radio frequency (RF) chamber. Based upon the color reaction of chromotropic acid with hexavalent chromium and the quantitative assessment using diphenyl carbazide, fixation was achieved in less than 6 hours. During heating, the temperature at various locations inside the pole sections was monitored by fiber-optic thermocouples. The moisture profiles before, and after fixation, were also recorded. Further studies will examine other benefit of RF heating, including a) sterilization, and b) rapid drying of round-wood with minimum check formation.
Fang Fang, J N R Ruddick
Influence of different fixation and ageing procedures on the leaching behaviour of copper from selected wood preservatives in laboratory trials
2003 - IRG/WP 03-20264
The paper focuses on the role of different parameters, such as fixation, sample size, wood species, and leaching in internationally standardized ageing procedures for wood preservatives from Europe, Japan and the United States. The leaching protocols used were EN 84, JIS K 1571 and AWPA E11 protocols. The wood species were Scots pine, Sugi and Southern Yellow Pine respectively. Three types of commercially important copper-based wood preservatives were used as model formulations, namely copper/copper-HDO, ammoniacal copper/quat and CCA. The most important factors determining the extent of copper leaching in the different lab trials were the sample size (volume/surface ratio) and the fixation conditions prior to leaching. On the other hand, the wood species and the leaching protocol itself were found to have only minor influence on the copper leaching rate in the test methods included in this study.
J Habicht, D Häntzschel, J Wittenzellner
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.
Problems of fixation of CCA-preservatives in palm-wood
1985 - IRG/WP 3338
Palm-wood may be used for posts and poles where it needs proper treatment for long time use. Based on observations by W. Killmann on low CCA-fixation in palm-wood, samples of Jubaea-palm grown in a Greenhouse at Hamburg, have been treated in two different series with a 4% solution of CCA-type B. After 1-16 weeks of storage the blocks were split into sticks of 1-2 mm² and leached. In all series 50% of the chromium and copper content of the individual blocks was leached independent of the time of storage, whereas simultaneously treated pinewood samples showed complete fixation after 4 weeks of storage.
H Willeitner, K Brandt
Radical changes in the requirements for more safe pressure impregnation in the Nordic countries in 1988
1990 - IRG/WP 3581
After introduction of quality control schemes and standards in the Nordic countries during the seventies, the first radical change of the standards and practice of work took place after pressure from the labor unions and authorities in 1988 and 1989 in Denmark and in Sweden. A new class of preservation with less retention for out of ground contact use was introduced, fixation times were prolonged to 6 and 14 days, and branding became a requirement. At the same time, treating companies replaced CCA with arsenic-free preservatives, and started using processes for accelerated fixation. Drying of treated wood was started to be used widely.
Accelerated fixation of CCA in borak bamboo (Bambusa balcooa Roxb.) of Bangladesh
2001 - IRG/WP 01-40193
CCA-C fixation study on impregnated (6% CCA solution), then boiled, oven-dried, normal, air-dried and steamed bamboo slices of air-dried borak bamboo (Bambusa balocca Roxb) of Bangladesh, revealed almost complete fixation in steamed (accelerated fixation) and air-dried (3 weeks, slow fixation) bamboo slices compared to moderate to slow fixation in boiled, oven-dried, normal and 24h air-dried slices.
A K Lahiry
A discussion of current theories concerning CCA fixation
1983 - IRG/WP 3238
The understanding of the fixation mechanism of CCA and related preservatives in wood has been greatly improved by a significant series of recent scientific papers. In view of recent concerns in New Zealand regarding the long-term efficacy of CCA in high decay-hazard situations, it was considered appropriate to review this recent work and to contrast it with theories presented by previous workers.
D V Plackett
A simple leaching procedure for in-plant monitoring of CCA fixation
1993 - IRG/WP 93-30023
A simple leaching test is described to quantitatively estimate the extent of fixation of chromated copper arsenate (CCA) preservative treated wood products. It is based on the reaction between diphenylcarbazide and unreacted hexavalent chromium leached from borings taken from treated wood during the fixation process. The test requires about 20 minutes to complete and can be set up in a treating plant quality control laboratory for less than US $1000.00.
P A Cooper, Y T Ung
Assessment of losses of wood preservatives from treated wood by leaching into the environment
1993 - IRG/WP 93-50001-13
Wood preservative chemicals may be lost from treated timber by leaching into water or soil. The degree to which this might occur and its effect on the environment is difficult to assess quantitatively due to the absence of appropriate test methods. This paper describes work to assess test methodology capable of allowing the rates of loss of wood preservative from treated timber to be quantified. The possibility of adapting simple laboratory equipment to monitor preservative losses from treated wood has been investigated. Losses due to leaching from selected faces of treated wood blocks when immersed in water have been monitored, using disodium octaborate as a model water-soluble preservative. The investigation has demonstrated the importance of distinguishing between transverse, radial and tangential surfaces when considering potential losses and the subsequent likely environmental impact of treated timber in service.
R J Orsler, G E Holland
nvestigation of anomalous fixation and leaching of CCA-treated red maple
2004 - IRG/WP 04-30341
The fixation of CCA-C preservative was investigated in red maple sawdust (Acer rubrum L.) at target retentions of 4.0, 6.4, 9.6 and 30.0 kg/m3. The effect of water-soluble extractives on the course of fixation was evaluated comparing the non-extracted with pre-extracted samples treated to 6.4 and 30 kg/m3. Leaching of the CCA components was monitored after complete fixation for all retentions. Fixation results show rapid chromium reduction, with the formation of a significant amount of water-soluble chromium complexes at lower retentions. Copper fixation was extremely fast while a substantial amount of arsenic remained unreacted. Leaching at the lower retentions was characterized by exceptionally high losses of arsenic and moderate losses of copper and chromium. Increase in the strength of the CCA solution consistently improved fixation and leaching of CCA in red maple. The observed anomalies were more pronounced for low retention levels. The presence of water-soluble low molecular weight carbohydrates, phenolic, and other extractives is likely the prominent factor responsible for the observed irregularities.
S Radivojevic, P A Cooper
Multiple-Phase Pressure (MPP) Process: One-stage CCA treatment and accelerated fixation process. 5. Treatment of Sitka spruce and Scots pine
1999 - IRG/WP 99-40136
The suitability of the MPP Process for CCA treatment and accelerated fixation of species other than Radiata pine was assessed by pilot plant trials on UK-grown Sitka spruce (Picea sitchensis) and Scots pine (Pinus sylvestris). Pressure and vacuum kickbacks of spruce (14 l/m3) and Scots' pine (122 l/m3) were both substantially lower than that generated during treatment of radiata pine (369 1/m). Total Organic Carbon (TOC) in kickback from spruce treatment (~ 750 ppm) was approximately half that in Scots pine kickback (~ 1400 ppm), and were substantially less than TOC generated during treatment of radiata pine (~ 2000 ppm). Extent of CCA fixation (spruce: 93%, Scots pine: 97%) was similar to that obtained with radiata pine (97%). To reduce post-treatment drippage, caused particularly by the refractory nature of spruce, a modified Bethell process was found most appropriate for MPP treatment rather than modified Lowry schedules used with radiata pine. Use of hot CCA solutions did not improve penetration into spruce and some collapse (washboarding) of early wood was a feature of its treatment.
M E Hedley, K Nasheri, G Durbin
The influence of previous anti-blue-stain preservative treatments on the fixation of CC in spruce
1997 - IRG/WP 97-30134
Freshly cut and kiln dried spruce boards were treated with 4 different anti-blue stain preservatives (ABP). After a period of 10 days allowing the samples to dry and fixate, the samples were treated with CC (chromium, copper formulation) using a vacuum pressure cycle. After impregnation the wood was steam fixed. A submersion leaching test showed differences in the leachable quantity of copper and chromium. When related to the retention of both salts after impregnation, no differences could be found between samples previously treated with anti-blue-stain preservatives and untreated samples. However, the retention of CC diminished significantly by application of quaternary ammonium compounds.
M Van der Zee, W J Homan
A short note on fungal decay in K33-treated poles
1982 - IRG/WP 1169
Soft rot cavities and erosion of the lumen have been found in K33-treated Pinus sylvestris poles from the years 1956-66 by microscopic studies. Poor treatment quality has been proved for some of these poles. The microscopy showed an unusual pattern of attack, and pre-treatment decay is suspected but not yet proved. Sounding the poles and using the Pilodyn indicated decay, but poking did not. Quantification of the attacks was possible only by microscopic studies.
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.
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
A fixation model, based on the temperature dependence of CCA-C fixation
2000 - IRG/WP 00-40163
A model was prepared for the fixation of 1% CCA-C in red pine that allows the prediction of extent of fixation based on the temperature history of the treated wood following pressure treatment. The reaction kinetics of the rapid initial reaction and the slower main reaction were characterized using the Van t'Hoff equation. The initial reaction could be represented by a 10th order chemical reaction and the main reaction by a first order chemical reaction. The main reaction zone in red pine starts once approximately 47% of the total Cr VI in the impregnated CCA-C solution is fixed on wood matrix and is much slower so it controls the fixation rate. The rate constants for the two zones were estimated at a range of fixation temperatures and the temperature dependence defined by the Arrhenius equation. The rate equation and the temperature dependence were combined in a single model for each fixation zone providing an equation that related extent of fixation to the time/temperature history following fixation. The model accurately predicted fixation rate of pine poles exposed to variable temperature conditions following treatment in most cases, although slight changes in the reaction and Arrhenius constants due to natural variability in wood density and other properties could result in relatively large errors in some cases.
P A Cooper, K M F Kazi, Jianbin Chen, Y T Ung
Copper naphthenate-treated Southern Pine pole stubs in field exposure. -Part 2: Chemical characterization of full size pole stubs 12 years after treatment
2000 - IRG/WP 00-30246
This study examines the influence of pre-treatment and post-treatment steaming on the character and physio-chemical nature of copper naphthenate in hydrocarbon solvent treated pine in larger, pole diameter, pole stub-length samples. This work is the continuation of two projects that began almost a decade ago. Previous reports indicated that certain morphological changes might occur in small laboratory steamed samples of copper naphthenate treated southern pine. Toluene-methanol extraction, UV-Vis spectroscopy, X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM) were used to investigate the nature and properties of the copper naphthenate present in the wood after 12 years of exposure. The formation of solid cuprous oxide occurred regardless of pre- or post-steaming conditioning.
H M Barnes, D P Kamdem, M H Freeman
The variation in electrical resistance in the CCA-treated wood during the fixation
1989 - IRG/WP 3554
The curve commonly used in Scandinavia for describing the fixation period at different temperatures for CCA-impregnated wood is based on investigation by Dahlgren on the pH-variations in a mixture of sawdust and preservative solution. As far as we know there is no such investigation on solid wood. We have therefore measured the electrical resistance in CCA-treated solid wood to see if this will differ according to the different ion consentrations that are in the wood during the fixation process. Our investigation shows that the electrical resistance in the CCA-treated wood varies. At first the resistance will increase, then it will decrease and at last stabilize at a higher ohm-value than in the start. This variation may describe the fixation in the wood and perhaps be used to measure the fixation time at different temperatures for solid, impregnated wood.
F G Evans, B Nossen
Field Test Results after Nine Years for CCA and ACQ Preservative-treated Wood Fixed in Different Climates
2003 - IRG/WP 03-30303
During assessment of the ground contact stakes in the Norwegian test field, we have frequently found that the first visual rot attack is in the zone of the stakes, where the stakes have been in contact with each other during the fixation. These parts are usually light green, caused by the lack of light during fixation, compared to the rest of the stake surface, which has a darker colour. To investigate if light on the stakes during fixation can affect the durability of the treated wood, we started a test in 1993. CCA and ACQ treated stakes were tested according to EN 252. The stakes were treated with two retentions of each salt. One according to the Nordic Class A (for ground contact i.e. hazard class 4) and one lower retention (25 % of the class A retention. This is even lower than the Nordic class AB (HC 3) retention). Before exposure they were fixed in 7 different climates: 1) Normal fixation = 60 % RH and 25 °C, light days, dark nights for 7 days, 2) Dark fixation = normal fixation without light for 7 days, 3) UV-light fixation = normal fixation with UV-light 24 hours for 7 days, 4) Hot fixation = 95 % RH and 90 °C for 2 hours, 5) Cold fixation = 50 % RH and 10 °C for 30 days, 6) Dry fixation = 10 % RH and 50 °C, for 24 hours, 7) Wrapped fixation = each stake packed in black plastic foil, 50 °C and without light for 24 hours. The colour of the ACQ stakes varied from light green to black, depending on the fixation climates. These different colours and the durability results after 5 years were reported at the 30th IRG meeting in 1999. The different fixation procedures give only small differences in durability/rot index after 9 years in field test. Hot, dry and wrapped fixations give ACQ a better durability than CCA in the Nordic class A retention. None of the ACQ stakes were rejected in the first 9 years, while the CCA stakes had a few rejected stakes after 8 and 9 years caused by sot-rot. For the low retention, ACQ gives a better durability than CCA for all fixation procedure, but both preservatives had several rejected stakes.
F G Evans
Rapid leaching test
1991 - IRG/WP 2367
An accelerated test which is suitable for measuring the extent of metal fixation in both chromium and non chromium containing preservatives is described.
J A Cornfield, M Bacon, A Lyman, C Waldie, M R Gayles
1983 - IRG/WP 3268
Effect of leaching temperature and water acidity on the loss of metal elements from CCA treated timber in aquatic conditions. Part 2: Semi-industrial investigation
1995 - IRG/WP 95-50040-13
In continuation of previous leaching research on the quantification and modelling of metal elements released from CCA treated timber, a series of experiments has been carried out dealing with the influence of temperature and pH of the relative aquatic environment. The leaching method used is the Dutch prestandard for building materials, a long term static leaching test simulating practical bank-shoring situations. Parameters of study are type of fixation, wood species and specimen profiles. With decreasing water temperature, significantly less leaching of copper, chromium and arsenic is observed. An outdoors/indoors temperature ratio of 0.7 could be established. Increasing acidity of the leaching water mainly enhances the release of copper, whereas chromium and arsenic show a minimum leaching tendency at neutral pH. Both conditioning chamber fixation and steam fixation prove to be effective in fixing the metal elements in the wood substrate. With steam fixed timber, however, a higher loss of copper is observed during the early leaching cycles, due to the presence of copper salts on the wood surface. With regard to specimen profiles, boards in comparison with posts demonstrate a remarkable resistance to leaching of active ingredients, presumably due to the different heartwood/sapwood distribution and the specimen dimensions. In conclusion, the observations made confirm the results obtained from previous leaching studies. Converting the emission data into leaching fluxes, a highly correlated double logarithmic flux formula is regarded the best tool for curve fitting, however, for a limited time span. Other models which are more suitable for extrapolation of emitted quantities over a longer period of time are still under investigation. Likewise, proprotional metal ratios versus retention levels highlight the relativity of experimental data obtained with standard emission tests.
G M F Van Eetvelde, W J Homan, H Militz, M Stevens
The use of zirconium as an inert fixative for borates in preservation
2001 - IRG/WP 01-30256
Stand-alone borates have been used in internal protected situations as wood preservatives for about 60 years. They have not been deemed acceptable for external situations because of their leaching characteristics. Work carried out to reduce the leachability of borates has been reviewed briefly here, and a specific fixation agent based on zirconium has been tested in standard leaching and decay tests. It was found that the performance of zirconium could be optimized for fixation at specific drying temperatures and at higher formulation pH. Using sufficient quantities of ammoniacal zirconium carbonate and potassium zirconium carbonate such formulations are then able to pass both Standard European and American Wood-Preservers' Association methods designed for testing exterior wood preservatives. Formulations based on borate with a zirconium additive are probably suitable for use in exterior above ground and possibly ground contact situations. As only initial indicative tests have been carried out so far, further testing with a range of wood destroying organisms and field tests should be carried out to evaluate this system further.
J D Lloyd, J L Fogel, A Vizel
Literature survey on the permanence and distribution of salt-type wood preservatives
1969 - IRG/WP III 1B
The objective of this survey is generally to review some of the more important published work dealing with the distribution and permanence of salt-type waterborne wood preservatives in treated timber. The survey is limited to the major chrome-containing formulations and the classification system proposed by Becker (1964) has been adopted throughout. CK - chromium, copper (copper, chrome); CKA - chromium, copper, arsenic (copper, chrome, arsenate); CKB - chromium, copper, boron (copper, chrome, boron); CFK - chromium, fluorine, copper (copper, chrome, fluorine); CFA - chromium, fluorine, arsenic (fluor, chrome, arsenate); CF - chromium, fluorine (fluor, chrome). The literature compilation covers the performance of these preservatives assessed from laboratory tests, field tests and practical experience; their application and distribution in the treated wood; and their influence on materials such as glues, paints or metals and the wood itself. It is not the purpose of this survey to draw conclusions regarding the relative merits of the various formulations, the choice of a formulation in a given situation depending upon many factors outside the terms of reference of this review, and not all of a technical nature. In general, there is insufficient directly comparable data for a definitive assessment and in the few comparisons available special factors frequently apply.
Checking of sodium pentachlorophenate fixation in wood
1990 - IRG/WP 3620
In order to estimate the volatilization of sodium pentachlorophenate from treated wood, wood samples treated with pentachlorophenate were analysed after various durations of an EN 73 weathering The results giving no clear evidence of volatilization, treated wood samples were put in a test chamber with precise climatic conditions, the air used in the experiment being analysed. The pentachlorophenate content in air was quantified: 1.8 µg/m³
M Lamour, H Sageot