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The preliminary characterization of ß-1,4-xylanase of the brown-rot fungus Gloeophyllum trabeum
1990 - IRG/WP 1447
The extracellular ß-1,4-xylanase of the brown-rot fungus, Gloeophyllum trabeum, was isolated from crude extract by chromatofocusing method (PBE 94 column chromatography). The isoelectric point was estimated to 4.2-4.8 by cromatofocusing and 4.5 by isoelectric focusing (IEF). The molecular weight of the enzyme was estimated to 37,000 dalton by SDS-PAGE. The optimal temperature for the crude extract xylanase was +70°C. The enzyme stability, after 1 h incubation, decreased sharply above +60°C and pH 6.
A-C Ritschkoff, M Rättö, L Viikari


Dimensional stability and decay resistance of hot-melt self-bonded particleboard by surface benzylated pine chips
1991 - IRG/WP 3652
Akamatsu (Pinus densiflora Sieb. et Zucc: Japanese red pine) particles were pretreated with 40% NaOH solution and benzylated with benzyl chloride, and the surface of particle was converted into meltable materials. Hot-melt self bonded particleboard having smooth and high glossiness surface was prepared by hot pressing at 150°C and 1.96 MPa without using any conventional adhesives. Dimensional stability and decay resistance of the benzylated particleboard were evaluated. Particleboards made of benzylated particles having more than 38% of weight percent gain (WPG) showed that dimensional stability and decay resistance were superior to the conventional particleboard made by using phenolformaldehyde resin as a binder, because hydroxyl groups of wood were substituted by hydrophobic benzyl groups with benzylation. Though bending strength of the board was a little lower than control board due to the damage of benzylated particles during benzylation, its internal bonding strength was very high, because the hot-melting strengthened the inter-particle bonding.
M Kiguchi, K Yamamoto


Effects of acetylation on the dimensional stability and decay resistance of kenaf (Hibiscus cannabinus L.) fiberboard
1996 - IRG/WP 96-40059
The objective of this study was to investigate the influence of the acetylation treated kenaf fiber, Phenol formaldehyde resin content level, and three fungi species on the dimensional stability and decay resistance of high density non wood composition boards. A standard ASTM method was used to evaluate weight loss and thickness change. The linear shrinkage and expansion of each species were also determined. All specimens were exposed to decay chambers for 16 weeks. Test results indicated that most of the main factors significantly influence the thickness, length changes, and decay resistance of the high density kenaf fiberboards.
P Chow, T Harp, R Meimban, J A Youngquist, R M Rowell


A practical method to evaluate the dimensional stability of wood and wood products
1990 - IRG/WP 2342
This paper presents a new simple method to evaluate wood and wood products for their resistance to swelling and to assess wood preservatives for their ability to dimensionally stabilize treated wood exposed to water. Permeable wood of various dimensions and treated with different preserving chemicals have been measured for swelling in the radial and tangential direction during immersion in liquid water. The results indicate that a simple exponential function describing the dimension of the samples during immersion can be used to evaluate both the water-repellency and anti-swelling effectiveness of wood preserving chemicals. The results can be achieved in reasonable time, and the parameters of the function can be determined by a commercial desk-top computer program.
J P Hösli


Physical properties of ß-1,4-Xylanase produced by Postia (=Poria) placenta: Implications for the control of brown rot
1987 - IRG/WP 1318
The degradation of hemicelluloses is an early event in wood decay by brown-rot fungi. An understanding of the physical properties of hemicellulases may suggest target mechanisms for the development of new control agents. Endo-b-1,4-xylanase was partially purified by column chromatography from wood decayed by Postia (= Poria) placenta. The enzyme was extremely resistant to denaturing conditions; no loss of activity was detected after 2 h in 9 M urea or 6 M guanidine-HCl. Boiling the enzyme for 5 min in 2.5% SDS + 0.5% b-mercaptoethanol reduced its activity by 65%, as measured by the production of reducing sugars. The activity of a-D-galactosidase, another enzyme detected in large quantities in the decayed wood, was reduced by 98% under these conditions. Optimum pH and temperature ranges were pH 2-6 and 50-60°C, respectively. The enzyme appears to be a glycoprotein containing 50-60% carbohydrate (w/w); the carbohydrate moiety may protect the enzyme from adverse environmental conditions. The control of brown rot by in situ inactivation of xylanase may not be feasible because of the enzyme's extreme stability.
J A Micales, F Green III, C A Clausen, T L Highley


A new ground-contact wide-spectrum organic wood preservative: DNBP
1986 - IRG/WP 3358
A new organic wood preservative, which 25 years field tests have proved to be of efficiency and effectiveness comparable to CCA wood preservatives for ground-contact applications, is presented. Physical and chemical tests, supporting the long term field test results as well as indicating the characteristics of this preservative, are also presented.
W E Conradie, A Pizzi


Report of the meeting of the refractory timbers sub-group, Lappeenranta, Finland on 25 May 1989
1989 - IRG/WP 3561
The first meeting of this sub-group took place on Thursday 25 May and considered the following agenda: 1) Papers presented to the meeting "Performance of treated spruce in Canadian field test sites" by J.P.Hösli and E.E.Doyle, IRG/WP/3506 and "Performance of CCA treated spruce and pine in unsterilized soil" by A.J.Nurmi. 2) Future work areas for the sub-group 3) Membership of the sub-group 4) Circulation of information
R J Murphy


Water-repellent additive for CCA
1991 - IRG/WP 3655
Hickson have developed a water repellent additive for incorporation into copper-chromium-arsenate timber treatment solutions. The water repellent emulsion shows good stability in the treatment solution, is easily incorporated and applied in a single stage treatment. No modifications to the additive is safe to treatment schedule are usually needed and use. Weathering of the treated wood is substantially inhibited by the presence of the additive. Adhesion of paints is not affected.
P Warburton, R F Fox, J A Cornfield


An investigation into the stability of TBTO in LOSP-treated radiata pine
1987 - IRG/WP 3459
Nuclear magnetic resonance (NMR) spectroscopy and reverse phase paper chromatography were used to characterise the organotin compounds found in radiata pine treated with bis (tri-n-butyl) tin oxide (TBTO). Preliminary results indicate that the preservative is remarkably unstable in wood after light organic solvent preservative (LOSP) treatment. Significant decomposition of TBTO occurs in a matter of hours. White crystalline material observed on the surface of treated wood was identified as tributyltin acetate (TBTA). Other tributyltin esters, dibutyltin ethers, and butyltin chlorides were also identified.
K J Archer, R Meder


Localization of oxalate decarboxylase in the brown-rot fungus Postia placenta
1996 - IRG/WP 96-10161
Oxalate decarboxylase, the enzyme that breaks oxalic acid down into formic acid and carbon dioxide, was recently detected in mycelial extracts of the brown-rot fungus Postia placenta. Differential centrifugation was used to demonstrate that the enzyme is loosely associated with the hyphal surface. Enzyme activity can be removed by washing the hyphae with a low pH buffer. Only low levels of activity were detected in soluble and membrane-bound intracellular fractions. The presence of the enzyme on the hyphal surface and possibly in the hyphal sheath supports the hypothesis that this brown-rot fungus actively regulates the pH and oxalic acid concentration of its environment.
J A Micales


Treatment of particleboard with isocyanate resin to impart improved dimensional stability and water repellency
2000 - IRG/WP 00-40178
Standard particleboard panels (for interior use) of 16 mm nominal thickness were cut into samples measuring 6.4 mm x 78 mm2. The samples were divided into 4 end matched batches. Two batches were treated with isocyanate resin and cured. The other 2 batches were left untreated. One of the treated batched and 1 of the untreated batches were edge sealed with epoxy resin prior to isocyanate resin application. The weight and thickness of each samples was measured prior to placing the sample in a beaker of distilled water. The weight and thickness were measured periodically for 1 week. Treatment with isocyanate resin reduced the average weight gain of sealed samples compared to the controls after 1 week. The average weight gain after 144 hours was 37% and 63% respectively while unsealed samples achieved a weight gain of 37% and 100% respectively. The thickness swelling was also reduced in the sealed samples compared to the controls (10% and 17% respectively) and the unsealed samples had a thickness swelling of 9% and 21% respectively. The results show a reduction in the rate of moisture uptake (water repellency) and amount (dimensional stability). Further experiments are described comparing particleboard with solid wood, with and without isocyanate resin application.
K M Filcock, P Vinden


Effect of double-vacuum and vacuum-pressure impregnation with water-borne preservatives on the dimensional characteristics of spruce
1990 - IRG/WP 3613
Air-dried planed spruce (Picea abies) samples were treated with a water-borne preservative (micro-emulsion) and one oil-borne type both containing azaconazole and deltamethrin. Each set of samples contained equal number of specimens with different growth ring orientation, heartwood content and density. In addition to the preservative retention and the penetration of a.i., the swelling of the samples was measured immediately after impregnation and further after 6, 24 and 48 hours. The growth ring figure induced different uptake levels when the impregnation process was intensified. Gradual increase of tangential surfaces reduced the retention. The effect of the wood properties on liquid absorption seemed to be greater for the oil-borne treatment. Volumetric swelling of the test samples treated with the water-borne solutions ranged from 0,5 to 0,6% immediately after double-vacuum impregnation increasing to a maximum of 0,8% 6 hours later. Subsequent air-drying of treated samples did not produce checking nor deformation. The oil-borne preservative gave rise to a swelling 3 to 4 times less. A swelling of 0,8% for spruce treated with a water-borne preservative may be considered acceptable taking into consideration volumetric movement figures of 1 to 1,5% for tropical hardwood species, classified as low movement timbers.
J Van Acker, M Stevens, G Rustenburg


Lignin degradation by wood-degrading fungi
1986 - IRG/WP 1310
The wood-degrading white-rot fungus Phanerochaete chrysosporium, has been the subject of intensive research in recent years and, based upon isolation of the extracelluar enzyme ligninase, major advances have now been made toward elucidating the mechanism by which this fungus degrades lignin. From these developments, a model emerges which could explain the process by which wood-degrading fungi in general, attack lignin.
P J Harvey, H E Schoemaker, J M Palmer


Towards a colour assay of wood degradation
1982 - IRG/WP 2180
A colour assay for the enzyme catalase is described. Since the activity of this enzyme has previously been shown to be correlated with degree of wood degradation as determined by other methods, this assay may provide a rapid quantitative indicator of superficial and internal wood decay.
M A Line


Effects of the addition of polyethylene glycol to the CCA-C preservative treatment
1985 - IRG/WP 3337
A modification of the CCA-C wood preservative system for utility poles has been investigated to see if spur penetration into the poles is assisted during climbing. Addition of polyethylene glycol to the CCA system has been shown to accomplish this purpose. This paper addresses the effects of the addition of polyethylene glycol to other physical properties germane to utility poles.
W P Trumble, E E Messina


Biological degradation resistance of pine wood treated with dimethylol compounds
1989 - IRG/WP 3528
The study reports the increase of dimensional stability and biological degradation resistance of pine wood (Pinus sylvestris L) after impregnation with dimethyloldibydroxyethyleneurea. Decay resistance was determined according to BS 838:961. Nearly complete protection against Coniophora puteana, (Schum.ex Fr. Karst) weight loss of 2-3% was shown when modification, expressed as weight gain, exceeded 15%. Resistance to biological attack of modified wood is speculated to be due to modification of the wood components and cross linking with dimethyloldihydroxyethyleneurea.
C L Videlov


Heat treatment of wood strands for OSB production: Effect on the mechanical properties, water absorption and dimensional stability
2002 - IRG/WP 02-40238
The effect of heat treatment on the mechanical and physical properties of commercial OSB strands was evaluated. Heat treatment was applied under inert atmospheric conditions to wood strands. The aim of this study was to examine the heat treatment parameters to achieve significant reduction of thickness swelling (upon exposure to moisture in service) without causing excessive reductions in strength. Heat treatments of 200, 210, 220, 230, 240, 250, and 260°C for 20 minutes were applied and swelling tests were performed. Subsequently the modulus of rupture and modulus of elasticity were measured in wood strands. High temperature treatments resulted in significant reductions in thickness swelling of wood strands but resulted in 20% reductions of modulus of rupture and modulus of elasticity.
G J Goroyias, M D C Hale


Dimensional stability, biological resistance, and mechanical properties of phenol-resin-treated particleboard
1990 - IRG/WP 3622
Particleboards were treated with a low molecular-weight phenol-formaldehyde (PF) resin and their enhanced properties were evaluated. Besides dipping of particles in aqeous solutions of resin, and spraying of resin solutions before spray of the conventional phenol-formaldehyde resin for adhesive binder, one step treatment by spraying of the mixture of the low molecular-weight resin and the adhesive resin was also employed. After 2-hour boiling, the boards treated at 10% incorporated resin loading (IRL) retained 80% of their strength values in a dry condition. The internal bond strength increased with increasing IRLs, and the boards of 20% IRL showed twice of the value of untreated controls in the same level of board density. Treated particleboards resulted in a more dramatic reduction in the rate of swelling even at low resin loadings. Results obtained from accelerated laboratory tests on biodegradation suggested that incorporated resin-solids worked well to enhance decay and termite resistance of particleboards.
Y Imamura, H Kajita


N-tritylmorpholine as a potential marine wood protectant against teredinids and pholads - A preliminary evaluation
1983 - IRG/WP 497
The molluscicide, N-tritylmorpholine, is effective in eradicating certain fresh water snails, the intermediate hosts in the transmission of schistosomiasis in man. This preliminary study shows that N-tritylmorpholine is also active against wood-boring marine mollusks. Fine sapwood impregnated with this morpholino compound was not damaged by teredinids or pholads while exposed at two marine sites in Panama. Because of its extreme insolubility, N-tritylmorpholine becomes a very specific toxicant, affecting only those marine mollusks (teredinids and pholads) which bore into the treated wood.
J D Bultman, K K Parrish


Stability and performance of tributyltin compounds
1984 - IRG/WP 3275
Based on the critical examinations of the disputable permanence of tributyltin compounds in wood, this paper deals with a number of examinations of the relative evaporation, thermal stability and oxidation stability of some TBT-compounds. While thermal and oxidative stability is high for all TBT-species, the relative evaporation at elevated temperature is highly variable, and lowest for the TBT-esters examined. Evaporation measurements on treated wood confirm this order of precedence and stress the importance of the preservative formulation. The results also indicate that TBTO evaporates 2-3 times faster than TBTN. It is established that at high retention of TBT in wood the decomposition is slower than at low retention. This fact combined with the extra high retention of TBT in vacuum treated joints of window frames explains the fine record of non-failure for such windows, and the paper ends up with a calculation indicating the presence of sufficiently high amounts of tributyltin for effective fungicidal protection of Nordic class B impregnated windows for at least 20 years.
F Imsgard, B Jensen, H A B Landsiedel, H Plum


Biodegradation of acetylated southern pine and aspen composition boards
1994 - IRG/WP 94-40020
This objective of this study was to investigate the influence of the acetylation treated wood fiber, Phenol-formaldehyde resin content level, two wood fiber species, three fungi species on the dimensional stability and decay resistence of high density composition boards. A standard ASTM method was used to evaluate weight loss and thickness change. The linear shrinkage and expansion of each species were also determined. All specimens were exposed to decay chambers for 16 weeks. Test results indicated that most of the main factors significantly influence the thickness and length changes and the decay resistance of the high density composition boards.
P Chow, T Harp, R Meimban, J A Youngquist, R M Powell


Acetylation of lignocellulosic materials
1989 - IRG/WP 3516
A simplified procedure for the acetylation of lignocellulosic materials has been developed. The acetylation is done with a limited amount of liquid acetic anhydride without the addition of a catalyst or an organic co-solvent. Dimensional stability and biological resistance are both much improved by the acetylation. Equilibrium moisture content in acetylated material is considerably lower than in unmodified material. No reduction of bending strength was found for acetylated solid wood samples. The process can be employed for both fibers, wood particles and solid wood. The process is applicable to hardwoods and softwoods, including solid spruce wood, and to non-wood fibers such as jute.
P Larsson, A-M Tillman


The effect of high temperature and long pressing time on the dimensional stability and decay resistance of OSB
2002 - IRG/WP 02-40237
The exterior use of OSB is restricted because when it is exposed to wet conditions swelling, loss of internal bond strength (IB) and decay occur. In this study an alternative process of pressing which results in the production of dimensionally stable and a more decay resistant strandboard was investigated. Boards were pressed at elevated temperatures for prolonged pressing cycles and their physical (thickness swelling and water absorption after 2 and 24 hours soak), mechanical properties (IB, MOR, MOE) and decay resistance were assessed. Analysis of variance (ANOVA, p=0.005) between pressing time/temperature and each property tested were used for the assessment of the results. The decay resistance of the boards was tested according to a draft European standard (DD ENV 12038: 1996) with a slight modification to the sample size. Boards were tested against Coniophora puteana, Postia placenta, Trametes versicolor and Pleurotus ostreatus. The results of this study showed that the increase of pressing time and temperature resulted in significant reductions in the thickness swelling and water absorption of the boards. The treatment had little effect on board mechanical properties. The resistance to fungal biodegradation was significantly improved at the higher temperature / pressing time combinations tested. The results of this study show that the production of a dimensionally stable and a more decay resistant OSB is possible without excessive use of preservative chemicals. If adopted these findings may lead to the development of new wood-based panel products (non-preserved dimensional stable and decay resistant hazard class 3-OSB) which may replace preservative treated plywood and solid wood for many exterior construction applications.
G J Goroyias, M D C Hale


Physiologic response of Phanerochaete chrysosporium to exposure to triazole fungicides
1994 - IRG/WP 94-10066
Triazoles are increasingly important fungicides which are employed for a variety of applications included wood protection. Several recent studies suggest that white rot fungi are more tolerant of triazole compounds than other wood degrading fungi. Cultural studies using a white rot fungus, Phanerochaete chrysosporium, and 0.2 or 0.8 ppm of tebuconazole or propiconazole suggested that mycelial dry weight was most affected by the presence of triazoles. Extracellular carboxymethylcellulase, cellobiosidase and phenol oxidase activities were depressed but not inhibited by triazoles, while ß-glucosidase activity appeared to be slimulated by the presence of these biocides. The results suggest that white rot fungi may be less sensitive to triazoles and this diminished sensitivity may permit these fungi to become more important on wood treated with this biocide.
J J Morrell, R K Velicheti


Effects of Trichoderma harzianum on enzyme activity and oxalic acid production of Gloeophyllum trabeum in ponderosa pine sapwood blocks
1992 - IRG/WP 92-1550
The effect of a bioprotectant, Trichoderma harzianum, on the activity of Gloeophyllum trabeum was investigated using a wood wafer sandwich method. Wood weight loss was greatest with Gloeophyllum trabeum exposed wafers, intermediate with those exposed to both the bioprotectant and decay fungus, and lowest with the bioprotectant exposed wafers. Extracts of wood wafers after 2, 4, or 6 weeks of fungal exposure revealed that the bioprotectant depressed, but did not completely inhibit enzyme activity of the decay fungus. Analysis of extracts for oxalate content revealed that the bioprotectant had little effect on the levels of oxalate present. The results suggest that the bioprotectant was not capable of completely inhibiting the decay fungus. Further trials to evaluate the effect of prior bioprotectant colonization on basidiomycete activity are planned.
C M Sexton, J J Morrell


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