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Development of preservative treatment method using sub and super critical carbon dioxide
2007 - IRG/WP 07-40385
Significant efforts have been devoted for developing biocide impregnation method into wood materials using supercritical fluid. Developing better understandings of fluid phase and its effect on treatment results would facilitate a more rational development of supercritical fluid (SCF) impregnation. In this project, the preservative treatabilities under super- and sub-critical fluid conditions were evaluated using Pinus Radiata sapwood. Treating characteristics are discussed in relation to different fluid phases and treatabilities (biocide penetration, distribution, and retention).
Myeung-Won Cho, Sung-Mo Kang, Gyu-Hyeok Kim

A review of the configuration of bordered pits to stimulate the fluid flow
2005 - IRG/WP 05-40315
As the bordered pits have generally been thought to have an influence on the refractory nature of softwoods, structural behaviour of this conducting pathways is discussed according to the published literature. Various theories on the role of bordered pits to axial flow are expounded in respect to preservative treatment. Pit aspiration is also reviewed.
I Usta

Options for accelerated boron treatment: A practical review of alternatives
1985 - IRG/WP 3329
Boron wood preservatives are almost exclusively applied by momentary immersion and block diffusion storage. Alternative techniques are described which can be used to accelerate boron treatment. Diffusion coefficients have been derived to define the acceleration of diffusion with increasing temperature. Schedules are described for pressure impregnation of green timber, involving steam conditioning, evacuation and alternating pressure method treatment. Timber Preservation Authority penetration and retention requirements can be met in approximately 4-5 h. The optimum schedule, however, included a 12 hour holding period between steaming and preservative treatment. A method of applying boron preservatives as a vapour is described, Trimethyl borate vapour reacts with wood moisture to form boric acid. The kinetics of this reaction, however, are very fast. This limits treatment to timber dried to very low wood moisture contents.
P Vinden, T Fenton, K Nasheri

Direct measurement of fluid flow within wood
1986 - IRG/WP 2248
The problematics of fluid flow mechanism within wood using a permeability concept are highlighted, and the non-feasibility of a practical and versatile model is explained. An alternative method using a negative temperature coefficient thermistor to measure flow velocity directly is presented. The method has been verified in living trees and shows extreme sensitivity for flow above 1 meter/hour. For measuring lower velocities, the method needs improvement.
J P Hösli

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

Analysing the characteristic role of moisture content for drying and fluid flow in Sitka spruce. - Part 1: The drying process of sapwood and heartwood of two different thickness of Sitka spruce using a kiln. - Part 2: Effects of moisture content on longitudinal permeability of Sitka spruce in vertical variation of the tree
2000 - IRG/WP 00-40173
The characteristic role of the moisture content in Sitka spruce (Picea sitchensis (Bong.) Carr.) that grown in the United Kingdom was examined by this study on the basis of (1) the reduction of moisture content in two different thickness of sapwood and heartwood by kiln drying process, and (2) the effects of moisture content to the longitudinal void volume filled of tanalith-C by the full-cell process from base (1 m) to apex (3 m) of the tree in sapwood zone. Accordingly, conclusions on indication of the drying process of sapwood and heartwood, and vertical variation of longitudinal flow with effects of moisture were listed separately: (1) Comparison of Drying Characteristic of Sapwood and Heartwood: The two different thickness (300x30x30 mm3 and 300x20x20 mm3) of sapwood and heartwood of Sitka spruce was dried using the suggested drying schedule in kiln. The reduction of moisture was schematically diagrammed according to sapwood and heartwood stakes. The reduction of moisture followed the same downward trend that sapwood (S) loses more moisture than heartwood (H) although the small stakes of S and H lost moisture rapidly compared with the large ones. (2) Vertical Variation of Moisture Content and Longitudinal Permeability: The 90 kiln dried defect free sapwood stakes (150x25x25 mm3) of Sitka spruce was taken from base to apex of the trees at 1, 2 and 3 m above ground level. After having the determination of moisture content in each experimental stake, the treatment was carried out by the full-cell process with CCA preservative (Tanalith-C) using a model pressure treatment plant. Significant differences observed among the tree heights from 1 to 3 m showing that slightly increases of moisture content from base to apex and conversely decreases of longitudinal void volume filled by preservative fluid.
I Usta

The Phase Out of CCA in the United States
2002 - IRG/WP 02-50194
In mid-February, 2002 the Administrator of the United States Environmental Protection Agency, Christine Todd Whitman, announced that the US treated wood industry will have until the end of December 2003 to end residential uses for Chromated Copper Arsenate (CCA). Industrial uses of CCA will still be allowed after the December 2003 date. This paper explores the events that led up to the announcement by the US EPA Administrator.
J D Schert

Laboratory simulation of leaching from creosote treated wood in aquatic exposures
2000 - IRG/WP 00-50157
Creosote has a long history of use as a preservative particularly in industrial wood products, but its use has come under increasing scrutiny as a result of concerns about its potential effects on aquatic and terrestrial non-target organisms. Despite its long use, there is relatively little data on the rates of creosote loss in many exposures. In this report, we describe small scale leaching tank procedures for evaluating migration from creosote-treated Douglas-fir lumber exposed at 35°C under 0 flow rate conditions. Creosote component concentrations in the water column were quantified using solid phase microextraction and gas chromatography. As expected, migration rates were higher for lower boiling point fractions. Leaching in the first eight hours followed a linear relationship for acenaphthene, dibenzofuran, fluorene, phenanthrene and fluoranthene. Chemical concentrations arrived at a steady state after 24 hrs of leaching. Concentrations of all creosote components tested tended to be lower than their reported water solubilities, suggesting that other factors were influencing migration. Further analyses of the leaching system are planned. The results will be used to expand a model that simulates creosote loss from treated wood in flowing fresh water.
Ying Xiao, J Simonsen, J J Morrell

Vapour boron treatment of wood based panels: Further studies on mechanical properties
1993 - IRG/WP 93-30028
Samples of medium density fibreboard, chipboard and oriented strandboard were treated to two retentions of boric acid by vapour phase methods. The results of short term mechanical tests on this material were discussed by Hashim et al. (1992). The present paper discusses results with long term studies on bending and impact resistance with panel types. Long term tests of impact resistance showed no greater reduction in toughness of treated panels compared to control panels over the test period of one year
R Hashim, R J Murphy, D J Dickinson, J Dinwoodie

Alternative technologies for wood wastes recycling - Part B: Biotreatment of PCP- and creosote-treated wood
1998 - IRG/WP 98-50101-18 b
Alternative technologies have been investigated to detoxify treated wood. Two classes of organic compounds are studied. Creosote-treated wood are classified in France as dangerous wood wastes. A conventional incineration could be provided for these wood wastes but the cost of this elimination could be very high (> 2000 FFR/ton). For these reasons, we have tested two kinds of new processes as alternative ways. The developed strategy is described in this paper and illustrated by a few examples. Part B - The second one is based on an oxidative degradation of organic compounds directly in the wood: oxidative degradation by fungi. Few examples are presented in this paper. Three fungi are tested directly on treated wood. High levels of contaminants are tested around 0.6 g of PCP/kg and 3.7 g of 8 PAH/kg of wood. Few oxidation products generated by this biological treatment are identified. An ecotoxicological assessment is performed to validate this process. Technical feasibility of these developed processes as well as economic aspects are discussed,
S Legay, P Marchal, G Labat

Comparison of decay rates of preservative-treated stakes in field and fungus cellar tests. Results after 40 months fungal cellar exposure
1983 - IRG/WP 2200
Decay rates of preservative-treated Pinus radiata stakes during 40 months exposure in the FRI fungus cellar were compared with those of similarly treated material in a field test. Decay rates in the fungus cellar were from 4 to 100 times higher than in the field, although for the majority of preservatives the rate was between 7 and 12 times higher. The lag phase before onset of decay, noticeable with most of the preservatives in the field test, was largely eliminated in the fungus cellar. Possible reasons are given for inconsistencies in relative rates of decay of preservatives in the two tests.
M E Hedley

Bending properties of TCMTB-treated Southern pine sapwood using supercritical carbon dioxide impregnation process
1997 - IRG/WP 97-40080
The effects of elevated pressure and treatment with thiocyanomethylthiobenzothiazole (TCMTB) on the bending properties of Southern pine sapwood were evaluated at pressures ranging from 1,800 to 3,600 psi. All bending properties were affected to some extent by supercritical fluid treatment. Modulus of elasticity and work to maximum load were not significantly affected by pressure levels. Modulus of rupture differed among individual pressure levels, but the effects on bending strength were less definitive. TCMTB retention had little or no effect on properties, suggesting a lack of chemical interactions between the lignocellulosic matrix and this biocide. The effect of treatment on bending properties was unexpected as previous trials on smaller specimens and selected composite panels had shown no negative effects. Further trials of other wood samples with increased replication are planned to more fully understand potential treatment effects on strength properties.
Gyu-Hyeok Kim, S Kumar, E S Demessie, K L Levien, J J Morrell

Incorporation of phenyl boronic acid treatment with vapor phase formalization
1997 - IRG/WP 97-40083
Phenylboronic acid (PBA) treatment was incorporated with vapor phase formalization (VPF) in order to increase dimensional stability and boron fixation as well as enhancement of biological resistance. Five and ten hours VPF were applied after PBA treatment as 0.34, 0.50, 1.00 and 2.00% concs. aqueous solutions. Anti swelling efficiency (ASE) attended to 71% in specimens impregnated with 0.50% PBA solution followed by five hour VPF. Leachability test results were supportive to presume a possible chemical bonding of PBA and formaldehyde. Decay test results indicated that formalization imparts superior properties to PBA treated wood against test fungi Tyromyces palustris and Coriolus versicolor, each as brown- and white-rot fungus, respectively. Fungal attack was completely inhibited with five hours of VPF and PBA treatment at the lowest loading level in the study. Shorter formalization seems also appropriate to attain the required fungicidal effectiveness with a little amount of PBA retention. Weight loss caused by Formosan termite Coptotermes formosanus Shiraki could be lowered by PBA-VPF treatment system, in addition to considerable increase in termite mortality.
M K Yalinkilic, S Yusuf, T Yoshimura, W-Y Su, K Tsunoda, M Takahashi

The multi-phase pressure (MPP) process. One stage CCA treatment and accelerated fixation process - Concepts proved by repetitive pilot plant treatments
1997 - IRG/WP 97-40079
Twenty-four charges of radiate pine roundwood or sawn timber were treated using the MPP Process and hot CCA solution. Treated timber met the CCA retention and penetration requirements of the NZ Timber Preservation Council for Hazard Classes H3 to H5. The objectives of the trials were: (1) To "stress" CCA solution by repetitive heating, treating and cooling to determine its stability in the process; (2) to determine any effects of pre-drying regimes on the standard of treatment; (3) to determine the extent of fixation influenced by various treatment variables. At the finish of the trials, the working solution was clear with no propensity to sludging. Preservative element ratios remained constant throughout the trials. Wood moisture content at the time of treatment had, not unexpectedly, most effect on degree of fixation achieved. Kickback liquid contamination with residual CCA and organic carbon was greater when wood moisture contents were high.
A J Pendlebury, J A Drysdale, K Nasheri, H Pearson, M E Hedley

Effects of seed origin and site on both wood density and longitudinal fluid uptake of Sitka spruce (Picea sitchensis (Bong.) Carr.) with height in the tree grown in the United Kingdom
2002 - IRG/WP 02-40226
The variation in density and longitudinal fluid uptake was investigated in short specimens of wood taken from eight seed origins of Sitka spruce trees grown at two sites in the UK. Five trees of each seed origin at each site were sampled at three heights (1, 2 and 3 m above ground level). The density of the samples decreased with increasing height within the stem. This corresponded with increasing ring width. The change of the longitudinal fluid uptake from base to apex showed an inverse trend to density. Site had an effect on density and increased density reduced fluid uptake. Seed origin had a marked effect on density and fluid uptake but the two factors showed no correlation. Some seed origins showed a variety of desirable characteristics and recommendations are made for the selection of seed origins for further UK plantations based on growth rate, density, tree form and permeability.
I Usta, M D C Hale

Multiple-Phase Pressure (MPP) Process: Pilot plant trials for disposal of kickback using reverse osmosis membrane filtration
2001 - IRG/WP 01-40202
The MPP Process (a one-stage CCA treatment and accelerated fixation process) generates ~ 250 litres of kickback per cubic metre of timber treated. Composition of kickback is mainly wood sugars and traces of copper, chromium and arsenic. In pilot plant scale trials, MPP process kickback was filtered through a Reverse Osmosis (RO) membrane of a type found from earlier small-scale trials to be the most effective for this operation. To reduce the total organic carbon (TOC) from 2000 ppm to around 100 ppm in the shortest time, preliminary pilot plant trials showed an optimum operating temperature of 20°C and pressure of 25 bar . Using this schedule, a final trial was undertaken in which 300 litres of kickback was separated into 275 litres of permeate and 25 litres of retentate. TOC was reduced from around 2000 ppm down to 98-108 ppm and CCA to less than 1 ppm in the permeate. To determine whether the permeate could be used as make-up water in a treatment plant operation, CCA solutions (1.6% oxide) were prepared using 0, 50 and 100% permeate containing 0, 65.6 and 131.2 ppm TOC respectively. After heating to 75°C and cooling to room temperature daily for 21 days, there were no differences in the amount of CCA sludge produced in each solution, indicating that permeate could be safely used as make-up water at the treatment plant. Impregnating retentate into MPP-treated material was investigated as an option for its disposal.
H Pearson, G Durbin, M E Hedley

Trial to determine a suitable schedule for radial and longitudinal treatment of plug samples by comparison of changes in the fluid retention and the treated area
2001 - IRG/WP 01-40211
A full-cell process was carried out using different treatment schedules for radial and longitudinal samples because of the anisotrophy of flow. When timbers are impregnated with preservatives much better penetrations are obtained via the end grain than laterally (across the grain). Therefore, suitable schedules for radial and longitudinal flow directions were determined in an trial experiment using locally grown Sitka spruce, Queen Charlotte Islands (QCI) provenance, from Beddgelert Forest in North Wales. The full cell experimental schedules used were: initial vacuum 15 minutes at -0.84 bar and various pressure periods that was 5 bar pressure in radial flow direction for 15, 45, and 60 minutes, 3 bar pressure in longitudinal flow direction for 3, 6, and 9 minutes. No final vacuum was applied. After the treatment, the fluid uptake was calculated, and the fluid retention was determined on a whole-block basis. After fixation, plugs were dried and cut longitudinally through the centre and copper penetration was determined by spraying a 1% solution of Chrome Azurol-S on the cut surface and observing the blue colour indicative of copper. The preservative penetration was then measured by image analyser as depth (mm) and as total treated area (%). From the experimental data, it was concluded that the suitable schedules are 5 bar pressure for 45 minutes for the radial flow direction, and 3 bar pressure for 7 minutes for the longitudinal flow direction. Therefore these schedules are suggested to be used to examine the permeability of the different seed origins in both radial and longitudinal flow directions.
I Usta

Cellular and fractural failure after supercritical fluid impregnation of four wood species
2004 - IRG/WP 04-10503
Supercritical fluids (SCFs) have been investigated for delivering biocides into sawn wood. Pressure differentials during treatment may exceed the compressive or tensile strength perpendicular to grain, creating a potential for transverse deformations that exceed elastic strain limits. Wood treated by SCF processing with CO2, a potential biocide carrier, was inspected macroscopically and microscopically. Both cell wall damage and smooth fracture surfaces appeared in the cellular structure. Damage was related to the rates of pressurization and venting and appeared to be species-specific. Cell walls were damaged during pressurization, whereas fracture damage occurred during venting. Specimen dimensions, permeability and anatomical structure are critical variables in developing SCF processes for biocide treatment of wood and wood-based products.
M E Anderson, R J Leichti, J J Morrell

Penetration and distribution of styrene in pressure treated hardwoods
1997 - IRG/WP 97-40094
A styrene impregnation method was used to compare liquid distribution in several species as affected by flow direction, sapwood/heartwood, and method of impregnation. Twenty-five mm ( 1") cubes were cut from the sapwood and heartwood of red maple (Acer rubrum), white birch (Betula papyrifera), yellow poplar (Liriodendron tulipifera), trembling aspen (Populus tremuloides), red oak (Quercus rubra), basswood (Tilia americana), red pine (Pinus resinosa) and American beech (Fagus grandifolia). Samples at 20-25% MC were sealed to permit either radial only or tangential only penetration or left unsealed and vacuum or pressure treated with catalysed and pigmented styrene. The styrene was polymerized in situ and the gross retention and penetration evaluated and the distribution in various cell types evaluated by light microscope. There were higher retentions and penetrations for tangential flow than for radial flow for all examined hardwoods except for red oak; red pine also was penetrated more readily in the radial direction. For transverse flow, the fibres were the most important flow paths in most hardwoods, with relatively little ray penetration, except in oak and the red pine (softwood). In uncoated samples, the vessels were the main flow paths, as expected, but the fibres were also significantly penetrated.
P A Cooper, T S Janezic, U Srinivasan, A Omidvar

Leachability of didecyldimethylammonium chloride (a quaternary ammonium compound) from four wood species
1982 - IRG/WP 3204
Sapwood blocks prepared from red pine, ponderosa pine, southern yellow pine and hem-fir (a commercial mixture of western hemlock and amabilis fir) were treated with didecyldimethylammonium chloride, (an alkylammonium compound, AAC). After oven drying the blocks were vacuum impregnated with distilled water and subjected to a static leach cycle for 48 hours. The leachate was analyzed and the amount of AAC which leached from each wood species, calculated. The results showed that the leaching of didecyldimethylammonium chloride from ponderosa pine was not unusual, and that the amount of AAC leached for the various wood species increased in the order > red pine > ponderosa pine > southern yellow pine > hem fir.
J N R Ruddick, A R H Sam

Supercritical fluid impregnation of Douglas-fir heartwood with cyproconazole using temperature induced deposition
2003 - IRG/WP 03-40259
A limited understanding of the fundamental aspects of supercritical fluid (SCF) impregnation in wood remains an obstacle to the development of this technology. Developing a better understanding of the effects of various process parameters on treatment results would facilitate more rational development of SCF impregnation. In this project, the effect of treating period and specimen length on supercritical fluid impregnation of cyproconzaole was evaluated on Douglas-fir heartwood using temperature decrease to induce biocide deposition. The results showed that biocide movement was slower than expected, and suggested that diffusion was the primary phenomena accounting for biocide penetration into the interior of sample. Further trials will be required to better understand the mechanism of biocide movement.
Sung-Mo Kang, J J Morrell

Supercritical fluid treatment: Effects on bending strength of white spruce heartwood
1993 - IRG/WP 93-20008
The effects of supercritical carbon dioxide on wood strength were evaluated using white spruce heartwood, a species known to be especially susceptible to collapse during exposure to higher pressures. The effects of pressures of 2000 or 3600 psig and temperatures of 40 or 80°C were evaluated using 30 or 60 minute exposure periods. No significant differences were noted in modulus of rupture or modulus of elasticity between specimens treated with supercritical fluid at selected pressures, temperatures or exposure periods or between treated and untreated control samples. Furthermore, no evidence of crushing or deformation were noted in specimens exposed to higher pressures. These results indicate that exposure to supercritical conditions should not adversely affect material properties of spruce.
S M Smith, J J Morrell, E Sahle-Demessie, K L Levien

Alternative technologies for wood wastes recycling - Part A: Supercritical extraction of PAH compounds from wood wastes
1998 - IRG/WP 98-50101-18 a
Alternative technologies have been investigated to detoxify treated wood. Two classes of organic compounds are studied. Creosote-treated wood are classified in France as dangerous wood wastes. A conventional incineration could be provided for these wood wastes but the cost of this elimination could be very high (> 2000 FFR/ton). For these reasons, we have tested two kinds of new processes as alternative ways. The developed strategy is described in this paper and illustrated by a few examples. Part A - The first one is based on the use of supercritical fluid as C02 to solubilize organic compounds as organochlorine compounds and Polycyclic Aromatic Hydrocarbons (creosote) from treated wood. Kinetics results of this extractive process are presented on the basis of 200 g of wood.
L Schrive, C Perre, G Labat

Potential for using dip/supercritical fluid treatments for wood impregnation
2004 - IRG/WP 04-40276
While supercritical fluid impregnation offers tremendous potential for impregnating wood species that resist conventional liquid preservative treatments, the resulting treatments are often not uniform among samples in a charge or between charges. One factor that influences treatment is the dynamic change in pressure that occurs during introduction of the biocide laden supercritical fluid into the treatment vessel. Subcritical conditions during these time periods sharply reduce biocide solubility, setting the stage for more variable treatment results. One approach to limiting these variations would be to deliver a large percentage of the biocide into the wood prior to SCF treatment. This would place the biocide closer to their intended locations with in the wood as it was solubilized. The potential for using a dip treatment to deliver biocide into the wood surface followed by SCF impregnation was assessed using Douglas-fir heartwood blocks and cyproconazole. Dipping in biocide tended to produce slightly more uniform internal retentions, however, inclusion of otherwise untreated samples in the vessels indicated that biocide also diffused from the blocks into the SC-CO2 where it was available for uptake into other wood. The results suggest that surface loading of wood prior to SCF treatment produced only marginal gains in uptake and is probably not practical.
Sung-Mo Kang, J J Morrell

Methods for improving preservative penetration into wood: a review
2002 - IRG/WP 02-40227
Pressure treatment technologies have been available since the mid-1830's, but the processes used for wood treatment are still largely unable to overcome the fundamental limitations of flow through semi-permeable pit membranes. Instead, methods have arisen that attempt to improve treatability of the wood including incising, compression rolling, through boring, or radial drilling. Other approaches have altered the characteristics of the treatment fluid primarily by reducing viscosity. None of these methods has been completely successful. This paper reviews the methods employed to improve preservative penetration in wood and outlines research needs for addressing treatment of refractory wood species.
J J Morrell, P I Morris

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