Your search resulted in 197 documents. Displaying 25 entries per page.
Copper binding capacity of modified wood flour
1992 - IRG/WP 92-3709
Wood flour was modified by reaction with oxidising agents and CCA preservative. The copper chromium and arsenic were removed from the CCA treated wood flour by an acid leaching procedure. The modified wood flours were allowed to react with copper acetate solution and the level of copper fixation achieved was determined. The modified wood flours had greater affinity for copper ions present in solut...
N C Milowych, W B Banks, J A Cornfield
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 p...
A Pizzi
Kinetics and mechanism of fixation of Cu-Cr-As wood preservatives. Part 5: Effect of wood species and preservative composition on the leaching during storage
1975 - IRG/WP 354
Conversion reactions during storage of CCA treated wood take place even at and below the fiber saturation point as long as ion transport is possible. Increase in drying temperature increases the final pH of the treated wood and the leachability of Cu and decreases slightly the leachability of Cr, while the leachability of As is not affected. This temperature effect is considered to be of no techni...
S-E Dahlgren
Kinetics and mechanism of fixation of Cu-Cr-As wood preservatives. Part 6: The length of the primary precipitation period
1975 - IRG/WP 359
The end of the primary precipitation fixation period of CCA preservatives coincides with the first peak in pH versus time. This offers a simple way of estimating the duration of the period. The duration is determined by a number of factors and their interactions, the most important of which are: wood species (anatomy, natural pH, accessibility of reducing agents), preservative type, preservative c...
S-E Dahlgren
Studies of the mechanism of chromated-copper preservative. Fixation using electron spin resonance
1992 - IRG/WP 92-3701
Two softwoods and one hardwood species were treated with chromium trioxide, copper sulphate, chromated-copper wood preservative (CCA). The treated wood samples were analyzed during fixation by electron spin resonance (ESR). ESR spectra indicated that more than one Cr(V) species was generated from Cr(VI) soon after CCA treatment. The Cr(V) signal became strong within increased several hours followe...
K Yamamoto, J N R Ruddick
Kinetics and mechanism of fixation of Cu-Cr-As wood preservatives. Part 4: Conversion reactions during storage
1974 - IRG/WP 332
Precipitates simulating those produced in wood by preservative fixation reactions were prepared by the reduction of Boliden K 33 and Celcure AP solutions with hydrogen peroxide and hydrazine. The pH changes on aging at 20 and 50°C were studied and related to the chemistry of fixation previously described. Hydrolysis of copper arsenates may render arsenic acid temporarily water soluble pending pre...
S-E Dahlgren
A theoretical-industrial correlation and perspective on copper-based wood preservatives - a review of thermodynamic and kinetic aspects on copper-wood fixation mechanism
2009 - IRG/WP 09-30499
Copper was and it will continue to remain one of the key active component in wood protection industry. Over the past decades, a significant effort from R&D teams in industry, academia and research institutes was directed toward understanding the copper-wood fixation mechanism, optimising the copper retentions in the wood and reduce leaching in order to maximized performance, prolong the lifetime o...
R Craciun, M Maier, J Habicht
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 com...
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 ge...
G Ozanne
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 he...
Fang Fang, J N R Ruddick
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...
H Willeitner, K Brandt
A new concept of oxalic acid biosynthesis in physiology of copper-tolerant brown-rot fungi
2001 - IRG/WP 01-10394
Recently, a wide variety of roles of oxalic acid (oxalate) in wood decay systems have been receiving much attention. Copper tolerance of wood-rotting basidiomycetes has been believed to be due to the detoxification of copper wood preservatives by oxalate produced by these fungi. However, biochemical mechanism of oxalate biosynthesis in relation to physiology of wood-rotting fungi has not been eluc...
E Munir, T Hattori, M Shimada
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 slice...
A K Lahiry
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 ...
B Moldrup
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. T...
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. Fix...
S Radivojevic, P A Cooper
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
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...
M E Hedley, K Nasheri, G Durbin
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 pl...
P A Cooper, Y T Ung
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. Quant...
H Friis-Hansen
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 ...
M Van der Zee, W J Homan
Antifungal mechanism of dichloro-N-octylisothiazolone
1998 - IRG/WP 98-30183
4,5-dichloro-N-octylisothiazolin-3-one (DCOI) is a member of the isothiazolone class of preservatives, whose antimicrobial mechanism of action has been intensively studied over the last decade. DCOI has also been intensively studied for use in wood preservation. The isothiazolones are electrophilic molecules that rapidly react with thiol groups to form covalently bonded isothiazolone-thiol adducts. This ability to bond with thiol groups is crucial to their ability to act as preservatives.
Thiol groups are present in proteins as part of the amino acid cysteine, where they play an important role in maintaining protein structure and function. A number of enzymes have thiol groups at the site where the enzyme function is performed, and these thiol groups may participate in the enzyme reaction. If the isothiazolone reacts with this thiol group, the activity of the enzyme is inhibited. Our studies have shown that there are several enzymes in the Krebs cycle that are inhibited by isothiazolones and these enzymes are required to generate energy and perform many biosynthetic functions. Reflective of this, DCOI has been shown to be a rapid inhibitor of cellular respiration, causing the cell to cease consuming oxygen almost immediately upon contact with DCOI. The multiplicity of targets and their central importance to the metabolism of the cell, as well as the fact that all microbes use at least parts of the Krebs cycle, can be related to the low use levels and broad spectrum of activity of DCOI.
The antimicrobial mechanism of DCOI results in a potent rapid-acting preservative with a broad spectrum of antifungal and antibacterial activity that is effective at low levels.
J S Chapman, M A Diehl, K B Fearnside, L E Leightley
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...
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 labora...
H M Barnes, D P Kamdem, M H Freeman
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