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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


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


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


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


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


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


Evaluation of fluid distribution in pressure treated wood in different flow directions
2004 - IRG/WP 04-40281
Among different methods, polymerization technique was chosen to study distribution of fluid through cell types in treated wood. Red maple wood specimens with the size of 2 by 2 by 4 cm (radial, tangential and longitudinal, respectively) were prepared. Styrene monomer was used as the fluid for impregnation; because its physical properties such as surface tension, specific gravity and viscosity fall between those of many preservatives. Before impregnation, apart from the uncoated specimens, some samples were coated with epoxy resin such that lateral flow along with longitudinal flow could be studied. Full cell process with the exception of final vacuum was applied for impregnation. Thin sections from the treated wood were prepared to be microscopically examined for distribution study. The results indicated uniform fluid distribution in lateral flow (both in radial and tangential) and non-uniform distribution in longitudinal flow as well as flow in uncoated specimens. Since uniform distribution of preservative among different cell types is very important, it is recommended that in some cases such as poles, piles, posts and sleepers, end coating of wood should be done before impregnation.
A Omidvar, M H Schneider


Aspects of diffusion of boron through wood
1984 - IRG/WP 3298
Boron compounds have been shown to be toxic to a wide range of wood destroying insects and fungi. They are cheap, have low mammalian toxicity and their application in the treatment of wood does not demand specialized equipment. These attributes make them specially attractive to developing countries. Currently, however, little is known about the mechanism of diffusion of boron through wood. Effective treatment with boron preservatives requires good understanding of how the preservatives diffuse through wood. This paper presents a research proposal with the overall objective of determining the relative importance of structural wood components in determining diffusion rates.
S Iddi


Comparison of cubic and plug samples for preparation and data assembly in permeability study
2000 - IRG/WP 00-20197
In order to determine if plug experimental samples (PES: 30 x 15 mm2 diameter) could be used for inspection of wood permeability characteristics, radial and longitudinal flow directions were prepared according to either PES or cubic experimental samples (CES: 100 x 20 x 20 mm3) from the sapwood zone of Sitka spruce and treated by tanalith-C according to full-cell process. Results from the two preparation techniques agreed in the test to determine the mean percentage of void volume filled by liquid both radially and longitudinally, while the preparation process (i.e. machining, sealing, etc.) of the experimental samples and the period of the data collection was quite longer in CES than that for PES in either flow direction.
I Usta


New technique to analyze impregnation processes
1988 - IRG/WP 2304
Equipment has been developed to measure liquid flow in wood during impregnation processes. Basic principles of flow measurements using directly heated negative temperature coefficient thermistors, and some characteristics of the hardware developed are presented in this paper.
J P Hösli


Flow charts for termite and decay tests to determine the natural durability of Japanese cedar (Cryptomeria japonica D. Don)
2008 - IRG/WP 08-20385
This paper deals with the experimental flow charts that were used for determination the effects of fungal decay and termite attack on Sugi heartwood during the course of the study of “Comparative studies of natural durability of Japanese cedar (Cryptomeria japonica D. Don) among the geographic cultivate”, which was carried out by Usta et al (2006).
I Usta, S Doi


Creosote movement from treated wood immersed in fresh water: Initial PAH migration
2003 - IRG/WP 03-50201
Creosote has a long history of successful use as a wood preservative, but polycyclic aromatic hydrocarbons (PAHs) in this preservative have raised environmental concerns, particularly when creosote-treated wood is used in aquatic environments. A number of models have been developed to predict the risk of creosote use in aquatic environments, but one limitation of these models is a lack of data on the initial rates of creosote migration from treated wood. We examined the effect of flow rates on creosote migration from freshly treated wood immersed in fresh water. Creosote component levels declined to a steady state within 7 days, suggesting that creosote migration decreased sharply after an initial spike. The data will be used to enhance existing predictive models.
Sung-Mo Kang, J J Morrell, J Simonsen, S T Lebow


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


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


The treatment of sawn whitewood with organic solvent wood preservative
1982 - IRG/WP 3192
The impregnation schedules approved in the UK for the treatment of sawn European whitewood (Picea abies) with organic solvent borne preservatives result in comparitively high loadings relative to the limited depth of penetration they achieve. Results are presented, which show how substantial reduction in the overall loading may be achieved without concomitant reduction in penetration. A model for organic solvent behaviour is postulated as a basis to account for these findings.
L D A Saunders


Probing red maple pit membrane pore size at FSP and OD using polystyrene macromolecules
2001 - IRG/WP 01-40217
A modified solute exclusion technique was used to pressure impregnate a polystyrene molecular weight (MW) series dissolved in styrene into red maple samples at approximately the fiber saturation point (FSP) and oven dry (OD). Radial penetration was less than tangential and FSP less than OD. There was a marked penetration change with MW in the tangential direction, although there appeared to be a slight decrease in FSP penetration at the higher MW tested.
A Omidvar, M H Schneider, A R P Van Heiningen


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


Efficiency of wood impregnation processes
1980 - IRG/WP 3151
Many wood impregnation processes have been in use for a very long time, up to 150 years, but they have not been progressively modified. This paper considers impregnation processes in relation to current requirements, particularly impregnation efficiency and energy consumption. The term 'pore' is used throughout in its physical sense and is not confined to botanical 'pores'. SI units are used and, for convenience, atmospheric pressure is assumed to be exactly 100 N/m²; complete vacuum is 0 N/m². These observations and conclusions summarise an extensive programme of investigation at Penarth Research Centre involving creosote and water-borne preservatives, as well as a range of organic solvent preservatives.
B A Richardson


Studies of the ray parenchyma cell ends on the radial flow of Sitka spruce (Picea sitchensis)
2000 - IRG/WP 00-40164
It is widely accepted that either ray tracheids or ray parenchyma cells offer the major flow pathways radially for the impregnation of softwood with preservative chemicals. It is now generally recognised that, if radial flow does occur through ray parenchyma cells, the cross-field pits play a dominating role for the liquid movement in the radial direction. In this case, the radial flow of fluid is through the ray parenchyma cells to the longitudinal tracheids across cross-field pit apertures and then back again to the other ray parenchyma cells. It is in this context that cross-field pits which favours flow in the radial direction via a longitudinal route, and thus gives a long path length for radial flow. However, the presence of small channels (i.e. simple pits) between the two ray parenchyma cells may also have a recognisable influence on the radial flow, and exceed the continuous pathway for liquid movement. In this study, therefore, the anatomical structure (the end platform angle, the number of the simple pits per ray parenchyma cell end, their dimensions and the changes in dimensions across growth rings) of the ray parenchyma cell ends have been examined by scanning electron microscope (and microscopic images were then analysed by image analyser) to explain the differences in radial permeability between the extremes in the radial treatment data.
I Usta


A novel solvent penetration assessment technique for wood preservativation treatments using waterborne systems
1990 - IRG/WP 2346
Solvent and hence solute (a.i.) penetration during any wood preservation treatment cycle and the flow pathways taken by the solvent in the wood are crucial elements in determining the adequacy of any treatment. Inadequate solvent penetration into specimens or an inappropriate tissue throughflow pattern during impregnation will markedly affect the distribution pattern achieved by many non-diffusible preservative systems. There is to date no direct method of determining the pathways liquid solvents take during their penetration into wood. Currently used methods, such as directional gas permeability measurements are indirect and only provide indications of the relative potential for certain pathways in the wood to be used during liquid impregnation of wood. The following work describes the development and experimental trial of a technique using cryogenic electron microscopy for the direct visual determination of water penetration into samples of Pinus patula and its potential for use in Eucalyptus grandis.
A J Pendlebury, J Coetzee, E Sorfa, A Botha


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


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


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