Swelling Of Wood Research Articles

Hygric properties of Norway spruce and sycamore after incubation with two white rot fungi

Abstract In this study, changes in the hygroscopic properties of two main wood species for violin making, Norway spruce and sycamore, after treatment with Physisporinus vitreus and Xylaria longipes were investigated. Swelling and moisture sorption capacity of wood at the growth ring scale were visually and quantitatively assessed by thermal neutron radiography analysis. It was demonstrated that the fungal treatment improved the dimensional stability of both Norway spruce and sycamore, but also increased their moisture adsorption capacity. Dynamic vapor sorption tests and measurements of the changes in dimensions of the specimens in the laboratory were in good agreement with the results of neutron radiography analysis. The main difference between the moisture sorption of the untreated controls and treated wood was observed at high relative humidity, e.g., above 75%. The contradictory behavior of the increased hygroscopicity and reduced swelling was explained by selective degradation of the chemical components and condensation of the moisture content gained in the capillary voids that developed in the cell walls during fungal decay.

A Comparative Study of the Physical Properties of Thermally Treated Poplar and Plane Woods

Effects of heat treatment on some physical properties of poplar and plane wood specimens were investigated. The main aim was to compare effects of heat on some physical properties of low-density poplar wood and high-density oriental plane wood. Heat treatment was conducted at temperatures of 150 and 200 °C for 3 h in the presence of air at atmospheric pressure. After the heat treatment, the mass loss; oven-dried density; tangential, radial, and volumetric swelling; fiber saturation point; and moisture content were determined. Regression analyses between mass loss and volumetric swelling were performed. The findings were analyzed statistically with ANOVA and the T-test. The results showed that heat treatment at 200 °C influenced the physical properties of both poplar wood and plane tree wood. In addition, the heat treatment had a little greater effect on the swelling and fiber saturation point of poplar wood than it did on the properties of plane wood.

Wettability and liquid sorption of wood investigated by Wilhelmy plate method

The wettability of Scots pine veneers was investigated with different approaches using the Wilhelmy plate method. The probe liquids were water and octane, which differ; in that, water is able to swell the wood sample, whereas octane does not. Novel approaches based on the Wilhelmy plate method to study wettability, liquid penetration, and swelling behavior of wood veneers are introduced. First, immersion to constant depth was performed, and liquid uptake with time was evaluated. Different kinetic regimes, the fastest one associated with contact angle changes and the slowest regime associated with liquid sorption by capillary and diffusion, were observed. Two other approaches, imbibition at constant depth (with initial deeper immersion) and full immersion, were utilized in order to keep the contact angle constant during measurements. Dynamic wettability studies were done by a multi-cycle (10–20 cycles) Wilhelmy method. Based on this, the time-dependent swelling of wood and changes in sample perimeter could be obtained. Generally, water showed higher absorption than octane. In all wettability studies, and for both probe liquids, the penetration process starts with a fast initial sorption, which is followed by swelling in the case of water.

Changes in Swelling and Water Absorption of Wood Degraded by Brown Rot Fungi

This paper presents results of experimental laboratory establishment of changes in physical properties (swelling, water absorption) of timber (spruce, pine, oak) caused by wood-destroying fungi (Serpula lacrymans, Stereum hirsutum). The experiment was carried out using standard test samples (20x20x30 mm) prepared from new timber and subsequently exposed to the wood-destroying fungi under optimal growth conditions for the period of 10 to 30 days. Changes in physical properties were observed in the damaged samples in compliance with CSN 490126 (equivalent to ISO 4859-1982, equivalent to ISO 4860-1982) and CSN 490104 Czech National Standards. The experiment proved changes in the observed properties depending on the wood and fungi species and the duration of the exposure.

Modification of some Albanian wood properties through chemical treatment

A study was carried out to evaluate the influence of acetylation on physical properties and gluing ability of some Albanian woods. Three woods were studied: beech (Fagus sylvatica L.), poplar (Populus alba L.) and fir (Abies alba Mill.). For acetylation, pyridine and acetic anhydride were used. After treatment, all the samples were conditioned to 100% relative humidity of air and were measured according to radial and tangential directions. After that, the samples were ovendried and were weighed and measured again, calculating the shrinkage and wood percent gain. Again, the samples were reconditioned to 100% relative humidity of air, calculating the swelling. The volumetric shrinkages of acetylated poplar and beech resulted 4.05 and 8.5%, meanwhile for non acetylated samples 9.8 and 16.5%. Tangential shrinkage of acetylated fir was 2.2% and for non acetylated 6.5%. The volumetric swellings of acetylated poplar and beech resulted 4.2 and 9.3%, meanwhile for the non acetylated 10.8 and 19.8%. Tangential swelling of acetylated fir wood was 1.7 and 5.8% for non acetylated. It seems that acetylation reduced more than 50% the moisture-related dimensional changes of wood. Regarding gluing the shear strength of acetylated beech resulted 2.4 times less comparing with non acetylated one. Key words: Acetylation, gluing, shrinkage, strength, swelling, wood.

Protein Modifiers Generally Provide Limited Improvement in Wood Bond Strength of Soy Flour Adhesives

Abstract Soy flour adhesives using a polyamidoamine-epichlorohydrin (PAE) polymeric coreactant are used increasingly as wood adhesives for interior products. Although these adhesives give good performance, higher bond strength under wet conditions is desirable. Wet strength is important for accelerated tests involving the internal forces generated by the swelling of wood and plasticization of the adhesive with increasing humidity. Soy proteins are globular due to their hydrophobicity; thus, it was expected that adding modifiers to open the protein structure should improve protein–protein and protein–wood interactions to help withstand both internal and external forces applied to the bond. Because modifiers have been shown to improve the performance of soy protein isolate adhesives, use of these modifiers has been examined as a way to improve soy flour adhesives. Protein-disrupting chaotropic agents (urea, guanidine hydrochloride, and dicyandiamide), surfactants (sodium dodecyl sulfate or cetyltrimethylammonium bromide), and the cosolvent propylene glycol were all expected to provide increased protein–protein and protein–PAE interactions. Improved interactions would make the soy flour adhesives durable enough to better pass wet bond strength tests specified for most interior bonded wood products. However, no substantial improvement was seen in cured wood bond strengths in wet conditions for soy flour adhesives by adding any of these modifiers with or without PAE polymer addition. These results led to a proposal that carbohydrates, about 45 percent by weight of soy flour, are interfering with obtaining greater adhesive bond strengths from the protein portion of the flour.

Effect of nanoclay on water absorption and thickness swelling of wood based composite

The demand for wood composite products such as particle board has increased distinguishingly. Future of particle board is dependent on the cost reduction of the resin and effort to improve its performance under service condition. The amount of water absorbed influences the swelling of the composite in thickness which affects the mechanical properties of the composite. Nano technology plays a vital role in significantly improving physical and mechanical properties of composites due to their nanoscale size. In this study, Nanomer PGV and Nanomer1.44p nanoclays were used to produce particle board of Poplar species. Nano clays were used as reinforcement filler for urea formaldehyde resin by mechanical mixing. Scanning electron microscope images (SEM) and X-ray diffraction (XRD) confirmed the dispersion and exfoliation of nanoclays in the adhesive. Prolonged gelation time was observed for Nanomer PGV reinforced resin. Particle board of 12mm thickness with 700 kg/m3 were manufactured using nanoclay reinforced resin. Water absorption and thickness swelling were evaluated as per Indian standard, for the laboratory scale made particle board. Water absorption and thickness swelling of wood composite was significantly reduced by adding Nanomer1.44 p to the resin. However Nanomer PGV did not show suitable effect on the stability of water absorption and Thickness swelling of the particle board

Hygromorphic behaviour of cellular material: hysteretic swelling and shrinkage of wood probed by phase contrast X-ray tomography

Wood is a hygromorphic material, meaning it responds to changes in environmental humidity by changing its geometry. Its cellular biological structure swells during wetting and shrinks during drying. The origin of the moisture-induced deformation lies at the sub-cellular scale. The cell wall can be considered a composite material with stiff cellulose fibrils acting as reinforcement embedded in a hemicellulose/lignin matrix. The bulk of the cellulose fibrils, forming 50% of the cell wall, are oriented longitudinally, forming long-pitched helices. Both components of cell wall matrix are displaying swelling. Moisture sorption and, to a lesser degree, swelling/shrinkage are known to be hysteretic. We quantify the affine strains during the swelling and shrinkage using high resolution images obtained by phase contrast synchrotron X-ray tomography of wood samples of different porosities. The reversibility of the swelling/shrinkage is found for samples with controlled moisture sorption history. The deformation is more hysteretic for high than for low density samples. Swelling/shrinkage due to ad/desorption of water vapour displays also a non-affine component. The reversibility of the swelling/shrinkage indicates that the material has a structural capacity to show a persistent cellular geometry for a given moisture state and a structural composition that allows for moisture-induced transitional states. A collection of qualitative observations of small subsets of cells during swelling/shrinkage is further studied by simulating the observed behaviour. An anisotropic swelling coefficient of the cell wall is found to emerge and its origin is linked to the anisotropy of the cellulose fibrils arrangement in cell wall layers.

CHANGES IN SWELLING PROPERTIES AND MOISTURE UPTAKE RATE OF OIL-HEAT-TREATED POPLAR (POPULUS × EURAMERICANA CV. PANNÓNIA) WOOD

In this work, the effect of oil heat treatment (OHT) on the swelling properties and changes in the rate of moisture uptake of poplar wood (Populus × euramericana cv. Pannónia) were investigated. Eighteen different treatments (combinations of three vegetable oils, two temperatures, and three durations) were studied. The results showed that OHT decreases the equilibrium moisture content (EMC) and the swelling of poplar wood. The degree of swelling and the EMC are influenced by both the duration and temperature of treatment. With an increase in duration and temperature, the EMC decreased. Consequently, the anti-swelling efficiency (ASE) increased. OHT wood adsorbs less moisture than natural wood, but it reaches a maximum – EMC at the momentary climate – at the same time under all the investigated treatments. The moisture uptake is fastest in the beginning and thereafter it slows significantly. Decreasing the moisture uptake by OHT wood is due to the decreasing of its water storage capacity.

THE EFFECTS OF HEAT TREATMENT ON THE PHYSICAL PROPERTIES OF JUVENILE WOOD AND MATURE WOOD OF EUCALYPTUS GRANDIS

Heat treatment can be used to improve the physical properties and durability of wood. The results achieved by heat treatment can be affected significantly by various factors. Juvenile wood and mature wood from the same trunk have different properties, and the effects of heat treatment on their physical properties have not been well defined. Thus, a study to determine the differences in the physical properties of juvenile wood and mature wood of E. grandis after heat treatment was conducted. Samples of both types of wood were treated at temperatures of 120, 150, and 180 °C for durations of 4, 6, and 8 h. The results showed that the physical properties of juvenile and mature wood, e.g., swelling, moisture content, and fiber saturation point, did not decrease to the same extent. Mass loss of mature wood was higher than that of juvenile wood. Generally, percentage decreases of volumetric swelling, moisture content, and fiber saturation point of juvenile wood were more affected than those of mature wood.

Macroscopic and microscopic monitoring of swelling of beech wood after impregnation with furfuryl alcohol

Wood furfurylation is a modification method that improves several wood properties. Thereby wood is impregnated with a solution of furfuryl alcohol, catalysts and water, in general. The objective of this study was to understand the penetration of furfuryl alcohol into wood. Furthermore, a possible relationship between the substance amount and the swelling behaviour should be determined. To this end microscopic investigations were conducted to describe the temporal process of penetration and swelling. It was found that the swelling coefficients differ at the microscopic and macroscopic level. The microscopic swelling can reach twice the values of macroscopic swelling.

Physical and chemical changes in juvenile and mature woods of Pinus elliottii var. elliottii by thermal modification

This study is aimed at evaluating the effect of thermal treatment on the physical and chemical properties of juvenile and mature wood from Pinus elliottii. Boards were taken from 35-year-old P. elliottii var. elliottii trees. The boards were thermally modified at 200 °C in the Laboratory of Wood Drying and Preservation from UNESP, Botucatu, SP, in Brazil. The results indicated that the thermal modification caused: (1) decreases of 20.1 % and 16.1 % in the equilibrium moisture content and volumetric swelling of mature wood, respectively; (2) decreases of 22.9 % and 14.8 % in the respective properties of juvenile wood; (3) increases of 34.1 % and 89.2 % in the extractive content of juvenile and mature wood, respectively; and (4) decreases of 3.4 % and 4.6 % in the respective holocelluloses content due to degradation in the hemicelluloses. It was found that juvenile wood presents an adverse effect on the chemical modification caused by thermal treatments. The influence of thermal modification in juvenile wood was lower than in mature wood and caused a greater uniformity in the physico-chemical variations between these types of wood.

PREDICTING THICKNESS SWELLING OF HOT PRESSED WOOD STRANDS

Strand board can be manufactured from sawmill residues, branches, and crown wood left in the forest. The thickness swelling of these residues is quite different from that of mature wood and can have a negative effect on the physical and strength properties of strand board. A mixture of these materials and pressing conditions can be optimized by assessing thickness swelling of wood strands after pressing. Individual wood strands conditioned to 12% moisture content were hot-pressed at 105 °C to 50% of their original thickness and conditioned at 20 °C and 33%, 100%, and 0% relative humidity for 72 hours to determine their thickness swelling. A mechanical model consisting of springs and dashpots was superimposed on a stress relaxation curve to determine strain components with a view to predict thickness swelling. The data were interpreted by analysis of variance in conjunction with Fisher’s protected least significant difference method. The results showed a good agreement between measured and predicted thickness swelling of both juvenile and mature wood.

INVESTIGATION OF THE MECHANICAL INTERACTIONS AT THE INTERFACE OF WOOD-CEMENT COMPOSITES BY MEANS OF ELECTRONIC SPECKLE PATTERN INTERFEROMETRY

This study investigates the bonding behaviour of Norway spruce wood strands to a surrounding cement matrix. Effects of wood swelling and shrinking during cement curing were studied by using strands of various thicknesses. The deformation of the spruce wood strands and the surrounding cement matrix, as well as the interface between the wood and the cement were examined using Electronic Laser Speckle Interferometry (ESPI) while applying a pull-out load. Sample deformation was transformed to shear strain maps, showing which side of the strand was tightly bonded to the cement matrix. The analysis of the strain maps proved that all strands were tightly bonded to the cement matrix on only one side. No shear deformation was observed on the loosely bonded side, meaning that there was no adhesion on that side between the wood strand and the cement matrix. Manufacturing of strands results in different surface characteristics and surface roughness. Bringing together the ESPI results with the roughness measurements, it was shown that only the comparably rougher surface adheres to the cement matrix. In a cement bonded composite (CBC) made of lignocellulosics to a greater or lesser extent, only half of the contact area is therefore able to transfer load.

Badania nad wykorzystaniem eterów glikolu propylenowego jako rozpuszczalników w roztworach impregnatów stosowanych do wzmacniania polichromowanego drewna zabytkowego

The article describes research on the possibilities of application of nontoxic propylene glycol ethers as resins’ solvents used for strengthening impregnation treatment. The possibilities of their application were checked on example of 1-methoxypropan-2-ol and 1-(2-methoxy-1-methylethoxy)propan-2-ol in comparison with toluol, solvent commonly used for that purpose. Research undertook aspects important from the conservators’ point of view, such as viscosity of prepared solutions, solvents’ swelling properties, speed of evaporation from impregnated wood, homogeneity of consolidant distribution and the way of affecting paint layers. In conclusion, the solutions containing the tested propylene glycol ethers have high viscosity, high rate of wood swelling, long voltality and long retention time, cause extraction of coloured constituents from wood and because of it they considerably affect the colour of polychromy. Structural changes in priming and paint layers such as swelling, blistering and increase of porosity were also observed as well as significant and long-lasting decrease of their softening point

Efeito do tempo e da temperatura de modificação térmica na redução do inchamento máximo da madeira de <i>Eucalyptus grandis</i> Hill ex Maiden

A modificação térmica de madeiras é uma técnica que foi desenvolvida na década de 40 do século XX e tem sido largamente estudada e aplicada industrialmente na Europa. No Brasil a pesquisa neste tema ainda é pequena e pulverizada, porém vem ganhando destaque atualmente. O objetivo deste trabalho foi avaliar a influência do tempo e da temperatura de modificação térmica na redução do inchamento máximo da madeira de Eucalyptus grandis. De acordo com os resultados obtidos podem-se obter reduções do inchamento volumétrico máximo da madeira de Eucalyptus grandis superiores a 50%. Melhores resultados foram obtidos com a modificação térmica a temperatura de 230°C do que a 200°C. O fator temperatura foi mais significativo do que o fator tempo, uma vez que não houve diferença significativa entre os diferentes tempos utilizados (1, 2 e 3 horas). Não houve interação significativa entre estes fatores na modificação térmica.

Effect of Thermal Compression Treatment on the Surface Hardness, Vertical Density Propile and Thickness Swelling of Eucalyptus Wood Boards by Hot-pressing

Thermal treatment techniques are used for modifying wood and wood-based materials to improve dimensional stability and hygroscopicity. This study investigated the effects of press pressure and temperature on density, vertical density profile, thickness swelling and surface hardness of eucalyptus wood boards. The experimental wood boards were prepared from Turkish River Gum (<TEX>$Eucalyptus$</TEX> <TEX>$camaldulensis$</TEX> Dehn.). The surface hardness value increased with increasing press pressure in the treated groups. The application of a higher pressure at the same temperature level increased the amount of swelling of wood. It means that it is not needed for application of higher pressure to enhance the dimensional stability of wood. It is expected that it is possible to produce increased hardness, dimensional stability and durability by application of hot pressing treatment. This research showed that different press pressure and temperature values should be used to improve the performance properties of eucalyptus wood so that the end-use of the wood materials could be expanded.

Nano-based surface treatm effects on swelling, water sorption and hardness of wood

Untreated and nano-based compound treated chestnut, wild cherry, fir, and black pine wood samples were immersed in water at four different temperature levels. It was found that the nano-based compound was a very effective agent for lowering both the initial and maximum equilibrium transverse swelling of wood. However, the latter were found to have similar trends as the initial swelling properties. The surface treatment appeared not to improve the maximum water absorption. The highest average activation energy was calculated for chestnut (23.1 kJ/mole), followed by pine (20.2 kJ/mole), cherry (18.1 kJ/mole), and fir (16.2 kJ/mole). However, the nano-based treatment resulted in a small increase in activation energies of all wood species. It was found that absorption of water into wood as well as increasing temperature had a lowering effect on shore D hardness.

Changes caused by heat treatment in chemical composition and some physical properties of acacia hybrid sapwood

AbstractAcacia hybrid (Acacia mangium×auriculiformis) sapwood was heat-treated in nitrogen under laboratory conditions for 2–6 h at 210°C–230°C. Chemical composition and physical properties including water absorption and swelling were examined. The results showed that these properties were reduced significantly by heat treatment, and there is an interactive effect of temperature and time on them. Chemical changes of the wood surface were determined by X-ray photo-electron spectroscopy analysis. Results indicate that the O/C ratio decreases as a function of treatment intensity due to the migration of extractives and degradation products to the surface during heat treatment. The C1speaks showed an elevated content of lignin and extractives, whereas the hydroxyl group content was diminished with elevated treatment temperature. The O1speaks revealed an increase in the O1peak and confirmed the course of C1speaks. These results coincide with the decrease in water absorption and swelling of wood after heat treatment.

Improvement of water resistance and dimensional stability of wood through titanium dioxide coating

Abstract Moisture absorption and dimensional distortion are the major drawbacks of wood utilization as building material. In this study, poplar wood coated with a thin layer of titanium dioxide (TiO2) was prepared by the cosolvent-controlled hydrothermal method. Subsequently, its moisture absorption and dimensional stability were examined. Scanning electron microscopy analysis revealed that the wood substrate was closely and entirely covered with the TiO2 coat. Microscale features were visible despite masking of the ultrastructural features of the cell wall. To explore the effects of TiO2 coating on the water-repellency and dimensional stability of wood, a 90-day water immersion test was carried out. Results showed that water absorption and thickness swelling of TiO2-coated wood increase very slowly and minimally. Weight change after 90 days of water immersion was reduced to 20.5%, nearly one-tenth of untreated control wood, and that maximum cross-sectional relative swelling was only 1.2%. Specimens were conditioned for 3 months at 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% relative humidity (RH) to determine the effects of RH on moisture absorption and dimensional swelling of TiO2-coated wood. There was no change in weight after 3 months of being exposed to humidity conditions below 60%, whereas there was linear weight increase above 60% RH, but the maximum change was less than 6%. Cross-sectional relative swelling was less than 0.3% below 60% RH but increased as RH exceeded 60%. The maximum change was approximately 3%. Anisotropic thickness swelling of wood was almost eliminated after coating. It is obvious that TiO2 coating can act as a moisture barrier for wood and is an exceptionally strong water vapor-inhibiting shield under very humid conditions.