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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

Combined effects of the treatment of wood with formaldehyde
1978 - IRG/WP 3117
Treatment of fibrous materials with reagents in a vapor phase is neither new nor unique. Numerous examples exist in literature of vapor phase experiments on cellulose fibers and fabrics, and on wood. For many years the textile research and industry have used vapor phase processes for the treatment of textiles. The chemical modification of cellulose is based on different types of reactions e.g. esterification, alkylation, resin formation or polymerization, monomer grafting and crosslinking. Vapor phase treatment of wood offers certain potential advantages over the conventional liquid phase wood impregnation. The higher mobility of low molecular weight compounds in the gaseous state ensures a rapid, uniform and homogeneous distribution throughout the wood structure. The vapor phase treatment of wood is also a better approach from the standpoint of cell wall penetration. Bulking, which takes place in the cell wall only, means that less chemicals are required and that the final weight of the composite is limited. Furthermore, due to the low viscosity of a gas, the application of a lower pressure differential remains possible. Within the framework of a wood improvement programme carried out at the Laboratory of Wood Biology and Wood Technology (University of Ghent, Belgium) the treatments were based on the impregnation of wood with liquid synthetic monomers and with gaseous formaldehyde. The results of the hygroscopic and dimensional behaviour of the wood-plastic-combinations have been published previously. Other papers deal with the physical and chemical interactions between the synthetic products and the natural polymers of the cell wall. This contribution will be restricted to the treatment of wood with formaldehyde in the gaseous state.
M Stevens, J Schalck

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

Effects of boron treatments on partially decayed oak and pitch pine heartwood
1996 - IRG/WP 96-30106
This paper reports results of borate based preservative treatment and leaching experiments on partially decayed oak and pitch pine heartwood. Previous experiments have shown little damage is caused to sound timber of these types when treated with Polybor and Boracol 20 preservatives. This experiment was carried out to assess the suitability of selected borate based preservatives for use in historical ships' timbers and therefore the physical effects of these preservatives on such timber was investigated. The results indicate that weight losses incurred due to treatment with Polybor or Boracol 20 are no more damaging than those incurred by treatment with water. Weight changes were more apparent in decayed timber than in sound timber with greater uptakes in non-leached samples and greater weight losses in leached samples. However, comparable weight changes were recorded between water treated samples and preservative treated samples. Dimensional changes were minimal in most cases, the greatest found in non-leached Boracol 20 samples as expected. These results indicate that treatment with these preservatives is suitable for partially decayed oak and pitch pine heartwood.
S McCutcheon, G M Smith, J W Palfreyman, P Durrant

Steam/hold/APM boron treatment - Treatability trials with green gauged radiata pine
1987 - IRG/WP 3439
Freshly sawn 100 x 50 mm radiata pine was green gauged, steam conditioned and preservative treated with a mixture of borax and boric acid using a modified Alternating Pressure Method (APM) treatment schedule. A 12 hour holding period between steam conditioning and treatment resulted in the necessary moisture loss and moisture re-distribution to facilitate treatment to NZ Timber Preservation Authority preservative retention and distribution requirements.
P Vinden

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

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

Long-term performance of a "wax" type additive for use with water-borne pressure preservative treatments
2000 - IRG/WP 00-40159
Field performance results are updated for matched CCA treated decking boards with and without an emulsion water repellent additive incorporated with the initial pressure treatment. Decks have been exposured for over 9 years in Harrisburg, NC. Boards were evaluated for in-service and laboratory performance for water repellent efficacy, as well as additive loadings in the boards after this exposure. All results support that these additives can provide long-term protection against many of the physical defects that develop in pressure treated wood during exposure.
A R Zahora

Dimensional stabilization of wood with dimethylol compounds
1987 - IRG/WP 3412
This study showed that a substantial degree of dimensional stability can be imparted to wood by crosslinking with low concentrations of dimethyloldihydroxyethyleneurea. It was demonstrated that by selecting the right catalyst system the cure temperature can be reduced to the point that strength loss of the treated wood is minimized.
D D Nicholas, A D Williams

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

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

Three dimensional computer representations of growth of microbial populations in wood
1984 - IRG/WP 1243
Creosoted distribution poles inoculated with either Lentinus lepideus, biological control organisms including Triochoderma or combinations of both were extensively sampled to monitor the spread of organisms. A computer program which enabled the results to be portrayed in a three dimensional graphic form was developed and is illustrated. Results showed that computer mapping of this type usefully enabled microbial interactions in wood to be evaluated.
A Bruce, B King, C Bruce, G M Smith

Treatment of wood with formaldehyde. Acid catalysis of the reaction between formaldehyde and wood
1980 - IRG/WP 3146
Formaldehyde reacts with the free OH-groups in wood forming cross-linking bonds. The reaction can be brought about without any catalyst but in that case the activation energy is very high and high temperatures and long reaction times are needed. Normally, the reaction is catalysed by different acids. Acid catalysts, however, tend to degrade the cellulose and the wood matrix causing reduction in the strength of the wood. The effect of the specific properties of catalysts on the cross-linking and hydrolytic reactions as well as the reaction kinetics have been inadequately investigated. Investigations on the treatment of wood with formaldehyde were started in 1976 at the Forest Products Laboratory of the Technical Research Centre of Finland. In the beginning, HCl-catalysed treatments were used which proved to reduce the strength properties of wood rather strongly. In continued trials more satisfactory catalysts have been sought in order to achieve maximal formaldehyde cross-linking and minimal degradation of the wood. The tests have included various inorganic and organic acids and metal halides soluble in water as well as sulphur dioxide (SO2) and boron trifluoride (BF3) in vapour phase. Some of the results are reviewed in this paper.
T Vihavainen, K Piispanen, P Mansikkamäki

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

Effect of cyclic change of temperature on fungal growth and mass loss
1994 - IRG/WP 94-10065
For estimating the effect of cycling change of temparature on fungal growth, four Japanese species, sugi (Cryptomeria japonica), hinoki (Chamaecyparis obtusa), akamatsu (Pinus densiflora) and buna (Fagus crenata), four fungal species, Tyromyces palustris, Gloeophyllum trabeum, Coriolus versicolor, Pycnoporus coccineus, and five temperature conditions, 10, 20, 27, 35°C and cyclic temperature (20°C 12 hours and 30 or 27°C 12 hours) under constant humidity (75% RH) were examined. The results were summarised that the cyclic condition was rather high fungal growth rate in the case of majority of fungi tested but was not surely increased the mass loss of wood. This tendency is rather clear in the case of brown rot like Tyromyces palustris. The cyclic temperature conditions were not favorable to the groth of Serpula lacrymans.
K Suzuki, K Okada

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

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