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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

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

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

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

Biological resistance of aldehyde-treated wood
1994 - IRG/WP 94-40018
Biological resistance of wood treated with aldehyde cross-linking agents such as glyoxal, glutaraldehyde and dimethylol dihydroxy ethyleneurea (DMDHEU) were investigated. Sapwood blocks of Japanese cedar and Japanese beech, measuring 20 x 20 x 10 mm³ (T x R x L), were vacuum-impregnated at room temperature with 5-25% of aldehyde solutions. Blocks were kept in the solution for 1 week to gain the optimum swelling until they were sunk at the bottom, air-dried for 1 week, and cured at 120°C for 24 hours, under SO2-catalysis. After treatment, they were throughly rinsed in running water for several days to leach out the unreacted aldehyde agent. Biological resistance tests were conducted in laboratory by exposing to brown-rot fungus Tyromyces palustris, white-rot fungus Coriolus versicolor, and the two subterranean termites, Coptotermes formosanus and Reticulitermes speratus. Glutaraldehyde was most effective to eliminate the attack of Japanese cedar by all test organisms. Decay by both fungi was almost nil in the treated cedar even at the lowest 5% solution of this agent. A complete death of both termites was gained also in glutaraldehyde-treated cedar at the same concentration. DMDHEU treatment was also effective to enhance the biological resistance of Japanese cedar. Enhancement of biological resistance was recognized also in Japanese beech treated with these agents, but it was somewhat lower than in Japanese cedar. Such a difference might be related to the value of dimensional stability resulted from the treatments. Glyoxal treatment exihibited throughly a poor effect to improve the biological resistance and the dimensional stability of both wood species.
S Yusuf, Y Imamura, M Takahashi, K Minato

Influencia de la impregnación con soluciones tánicas en la estabilidad dimensional de la madera de Pinus pinaster Ait. procedente de España
1992 - IRG/WP 92-3686
En virtud de la importancia que presenta la madera de Pinus pinaster Ait. en el sector constructivo español, se ha sometido a esta a tratamientos en autoclave con distintas soluciones tánicas naturales y artificiales a fin de estudiar su incidencia en la estabilidad dimensional frente a exposiciones exteriores. En el estudio se pone de manifiesto el efecto creado por el tratamiento protector en la estabilidad dimensional de la madera tras exposición de las probetas durante el período de un año al exterior. Se evalúan las diferencias existentes entre maderas tratadas y no tratadas en lo que se refiere a las variaciones de volumen, humedad, y movimientos, empleándose probetas de dimensiones 5 x 5 x 100 cm³, colocadas con una inclinación de 45° y orientadas al Sur.
J A Rodríguez Barreal, J Cubillo Jordan de Urries, L Garcia Esteban

Thermal modification of non-durable wood species 1. The PLATO technology: thermal modification of wood
1998 - IRG/WP 98-40123
The PLATO technology is an innovative upgrading technology with low environmental impact, which can be applied to fast grown and non-durable wood species. This technology is based on a thermal modification of solid wood without the addition of chemicals (e.g. preservatives), consisting of a hydrothermal treatment, followed by drying and curing. The PLATO technology results in a substantial improvement of the natural durability and dimensional stability of wood with only a slight reduction in mechanical properties. Applications of thermally modified wood will include areas where a good durability and/or dimensional stability is required, e.g. garden wood and furniture, wooden sheds, canal lining, joinery, window frames, doors, claddings. In 1998/99 the PLATO technology will be commercialised in the Netherlands. In this paper features of the PLATO technology will be discussed, including selection of wood species, the PLATO process and product development, product properties and applications.
M J Boonstra, B F Tjeerdsma, H A C Groeneveld

Improvements of stability and durability of beechwood (Fagus sylvatica) by means of treatment with acetic anhydride
1991 - IRG/WP 3645
In the present investigations, beechwood (Fagus sylvatica) was treated with non-catalysed acetic anhydrid at 120°C and some physical- and biological parameters of the treated wood were compared with those of non-treated wood. The radial and tangential shrinkage and swelling, respectively, and the absorption capacity of the acetylated wood against moisture is considerably lower. The durability against fungi improves. The results are discussed.
H Militz

Influence of concentration, catalyst, and temperature on dimensional stability of DMDHEU modified scots pine
1998 - IRG/WP 98-40119
Dimethyloldihydroxyethyleneurea (DMDHEU) is being used in textile industry to improve wrinkle recovery. Trials on solid wood have been performed to minimise swelling of the wood. This paper focuses on the effect of various types and concentrations of catalyst and reaction temperature on the dimensional stability of Scots pine. Three different catalysts, NKS (based on magnesium chloride), 3282 (based on aluminium chloride) and citric acid have been tried separately or in combination with tartaric acid. Reaction temperatures between 100° and 125°C have been investigated. The results showed that an anti shrink efficiency of up to 50% can be obtained.
M Van der Zee, E P J Beckers, H Militz

Soil bed studies of the dimensional stability of composite products
1999 - IRG/WP 99-40134
The influence of boron and isocyanate resin on the dimensional stability of high moisture resistant particleboard was assessed after burial in a soil bed for one month. The samples were treated with two levels of a boron compound and coated in isocyanate resin. The samples were randomly placed in a fungal cellar in soils of two different water holding capacities. Weight differences and dimensional changes were measured after one month. The results suggest that there is a significant increase in weight and thickness swelling. Boron treatment prior to resin impregnation also appears to have assisted moisture absorption.
K M Filcock, P Vinden

Effect of boron compounds-furfuryl alcohol treatment of wood on dimensional stability, termite resistance and boron leachability
2001 - IRG/WP 01-40195
Sapwood blocks of Japanese cedar (Cryptomeria japonica) and Caribbean pitch pine (Pinus caribaea) measuring 20 (tangential) x 20 (radial) x 10 (longitudinal) mm were impregnated with furfuryl alcohol (FFA) by a vacuum-diffusion process followed by curing under heating. Boron compounds (boric acid, ammonium borate and ammonium biborate) were mixed in the impregnation solution of FFA. Anti- swelling efficiency, water holding capacity and moisture exclusion efficiency were measured. Boron leachability was determined by ion chromatography with ten leaching cycles according to JIS 9201 (1992). The specimens were exposed to termite attack testing, before and after the cyclic leaching process. The results indicated that FFA imparted to wood greater dimensional stability when mixed with boron compounds. Boron when mixed with FFA behaved differently to boron alone treatment, although it was still leachable. The wood specimens treated with FFA-boron compounds were quite resistant to termites even after severe leaching.
S K Ozaki, M K Yalinkilic, Y Imamura, M F Souza

The Protection of Wood with Oxy-aluminium Compounds
2002 - IRG/WP 02-30286
Wood inorganic composites (WICs) containing aluminium compounds were developed and tested in relation to some essential requirements of preservative treated wood. Four different oxy-aluminium treatments were developed and identified according to the final insoluble compounds formed (sodium aluminate, aluminium hydroxide, magnesium aluminate and aluminium borate) in wood. Vacuum impregnation or double diffusion were used as delivery systems for the chemicals. Higher weight percent gains were obtained when wood was treated by vacuum impregnation. Inorganic deposits were detected throughout the structure of treated wood using scanning electron microscopy. A high degree of dimensional stability was imparted to Scots pine by the treatments, and significant dimensional stability was retained even after treated wood was subjected to cold-water leaching. The oxy-aluminium treatments did not, however, impart water-repellency to wood. The decay resistance of oxy-aluminium treated wood, which was assessed through the use of terrestrial microcosms, was dependent on treatment, soil type and temperature, and exposure times. Oxy-aluminium treated wood showed increased resistance to brown rot. Sodium aluminate and aluminium hydroxide were more effective than magnesium aluminate and aluminium borate in protecting wood against soft rot. The results suggest that it is possible to protect some important wood properties with the use of oxy-aluminium compounds. Further research is needed to fully explore the potential of oxy-aluminium treatments for the protection of wood.
F A Ximenes, P D Evans

Thermal modification of non-durable wood species 2. Improved wood properties of thermal treated wood
1998 - IRG/WP 98-40124
Properties of wood treated in a new heat-treatment process called the PLATO-process have been studied. Several wood species have been treated using this new thermal modification process using a range of process conditions (mainly time and temperature). In this study the characteristics of the treated wood were determined using samples from whole planks treated on pilot plant scale. The modified chemical structure of the wood after treatment results in a product with improved properties. The most important properties of wood, strength, dimensional stability and durability, were determined before and after the heat-treatment. The examined wood species showed a minor loss of strength after treatment. The correlation between the hygroscopicity of the treated wood in moist conditions and the dimensional stability has been studied. Depending on the applied process conditions the hygroscopicity of the treated wood decreased. The hygroscopicity was reduced by 40% and the dimensional stability appeared to have an improvement, ranging to 50%. The durability after heat-treatment was substantially improved.
B F Tjeerdsma, M J Boonstra, H Militz

The use of natural and synthetical tannins to improve the dimensional stability and durability of beechwood (Fagus sylvatica)
1993 - IRG/WP 93-30016
Synthetical tannins and natural extractives of oak, spruce and chestnut have been combined with different fungicides to make the wood more dimensionally stable and more durable. The anti-shrink-efficiency and the improvement of the durability of different synthetical and natural tannins have been evaluated. The results make clear, that an application of the mentioned agents for common use cannot be recommended without further preface. Under "moist" conditions (high relative humidity) none of the tested tannin/preservatives seem suitable for the treatment of beechwood. All the combinations of tannins and preservatives are hygroscopic and poor in fixation and therefore leach quickly. The result of the soil block test too, (approx. 15% weight loss of specimens at relative high loadings of preservatives) is not sufficient to recommend application. Further research has to demonstrate, whether with softwood species better results can be achieved. Furthermore, different concentrations of the most promising agents (tannins and chromium containing salts) have to be tested to determine optimum retentions and toxic values before and after leaching. A considerable improvement of the dimensional properties (ASE 50-75%) was obtained by a treatment with Tannin AKF in ranges of low relative humidities (0-60% RH). Under these dry conditions, however, no fungicides are needed.
H Militz, W J Homan

Dimensional stability and decay resistance of wood upon modification with some new type chemical reactants
1994 - IRG/WP 94-40028
Solid wood of home grown species can be upgraded by chemical modification with environmentally acceptable chemicals. The best kwown example of modification reaction is acetylation with acetic anhydride. A continued search for reactive chemicals other than acetic anhydride is ongoing, aiming at the improvement of technical properties of wood. This contribution deals with the results of a screening experiment of different potential chemicals for modification reactions. The following reactive chemicals were selected for the treatment of small wood blocks: glutaric anhydride wether or not in combination with epichlorohydrin; cyclohexylisocyanate; glycidylmethacrylate; propyltrimethoxysilane and sodiumperiodate. The dimensional behaviour (ASE-values; water vapour sorption) and chemical stability (hydrolysis) of modified samples at different weight add-on levels were examined. Decay resistance was tested for all modified samples against Coniophora puteana (pine) and Coriolus versicolor (beech). Esterified wood at a WPG of 25% affords the highest level of improvement to both pine and beech, with ASE-values of 50 up to 70% and low weight losses on fungal exposure, particulary for treated pine.
P Goethals, M Stevens

Improvement in dimensional stability against water of the main Spanish timbers impregnated with water repellent organic protectors
1988 - IRG/WP 3468
The study reported the increase of dimensional stability against water of the main Spanish timbers, both broadleaved and coniferous, after impregnation in the autoclave with organic protector, with contains 33.3% water repellent waxes and resins. The proposed Spanish standard, U.N.E. n° 56541 is used, where dimensional stability of the impregnated wood is expressed as a% of that of the non-impregnated wood. Account is taken of the effects of lamination on dimensional stability, cold resorcin glues bring used for lamination. A series of curves representing swelling againts immersion time were thus obtaines, as well as the dimensional stability value for each species. The highest values were achieved with coniferous laminated and the lowest with non-laminated broadleaved timbers (Dimensional stability).
J A Rodríguez Barreal

Durability of Wood/Plastic Composites Made From Parthenium species
2002 - IRG/WP 02-40225
Previous study indicated that the natural chemical constituents of the guayule plant (Parthenium argentatum) improved some durability properties of wood when it was treated with resin extracted from guayule. At present, there are about a dozen species of Parthenium growing in the North American continent. P. argentatum is the only species with harvestable amounts of the rubber latex. Other species such as P. incanum and P. tomentosum produce primarily resinous materials, but which could be as useful as the P. argentatum species for making composites. The predicted commercialization of guayule for its hypoallergenic latex will result in a significant amount of waste plant material or bagasse that can be put to use in making wood products and would otherwise be a disposal problem. Thus, the guayule fiber residues can be a source of natural wood preservative to improve the durability of wood/plastic composites. Preliminary laboratory tests were conducted to determine the resistance of wood/plastic composites made from three Parthenium species against Eastern subterranean termite. The physical properties of these three types of composites were also measured, namely dimensional stability (water absorption, thickness swelling, two-hour boil, and linear expansion), and the strength properties such as bending and internal-bond (IB) or tensile stress perpendicular to face. The results were compared with a wood/plastic composite made from the commercial pine wood flour or fibers.
P Chow, F S Nakayama , J A Youngquist, J H Muehl, A M Krzysik

The effect of heat treatment on the properties of spruce
1994 - IRG/WP 94-40032
The effect of high temperature treatment (above 150°C) on the wood quality is studied at the VTT. Improved dimensional stability, lower equilibrium moisture content and increased durability against biodeterioration is achieved, depending on the environmental factors. The biodeterioration resistance of spruce is improved due to changes in chemical composition and lower equilibrium moisture content. As a result of the treatment, darkening of colour and reduction of the strenght of the wood due to changes in microstructure is also observed.
H Viitanen, S Jämsä, L Paajanen, A J Nurmi, P Viitaniemi

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