Comparison of mechanical properties of oriented strand board made from trembling aspen and paper birch

This study compared the performance of oriented strand boards (OSB) made from trembling aspen, a low-density hardwood species, and OSB made from paper birch, a medium-density hardwood species. The birch strands were thinner than the aspen strands to ensure a comparable specific surface. Three levels of adhesive content were used: 3.5%, 5.0%, and 7.0%. Internal bond (IB) and modulus of elasticity (MOE) and modulus of rupture (MOR) for flatwise and edgewise bending were determined. Both species performed equally well in IB (3.5% adhesive content: 0.46 MPa, 5.0%: 0.60 MPa, and 7.0%: 0.65 MPa). The values of MOE in flatwise bending were slightly lower for birch than for aspen panels (11.8 GPa for aspen and 10.6 GPa for birch), and the MOR values were not significantly different (combined 68.3 MPa). Edgewise bending properties were not significantly different for the two species with a MOE of 10.5 GPa and a MOR of 43.2 MPa.     

The effect of fine strands in core layer on physical and mechanical properties of oriented strand boards (OSB) made of beech (Fagus sylvatica) and poplar (Populus tremula)

This paper discusses the influence of three different content levels of fine strands in the core layers on the physical and mechanical properties of European beech and poplar oriented strand boards (OSB). The results show that increasing the fines content in the core layer from 10 to 50 %, based on total board weight has no significant effect on bending strength and modulus of elasticity (MOE). All panels exceeded the minimum requirement for bending strength and MOE set by EN standards. The highest modulus of rupture (MOR) and modulus of elasticity (MOE) was determined for panels solely made of poplar with different level of fines content. Increasing the amount of fines in the core layer raised the internal bond (IB). Panels made with 30 % fines in the core layer showed highest internal bond strength values. As the fines content increased from 10 to 50 %, thickness swelling decreased. Water absorption after 24 h showed the same declining trend as thickness swelling.     

Oriented Strandboard (OSB) Panels Made from Kenaf Stalks and Aspen

Abstract

The specific gravity of these panels varied from 0.68 to 0.75. The amount of kenaf, resin content significantly affected the modulus of rupture and the modulus of elasticity values of aspen-kenaf boards. Boards with 25% kenaf and 75% aspen produced MOR and MOE values comparable to commercial oriented strandboard (OSB). Percentage of kenaf and resin levels were significant factors influencing the internal bond (IB) strength when compared to the commercial OSB. The 25% kenaf and 75% aspen boards produced IB values that could meet the required standard. Aspen-kenaf boards obtained lower values for linear expansion. Lower percentage of kenaf flakes and higher resin content controlled thickness swelling. However, boards with 50% kenaf and 50% aspen flakes made with 6% resin resulted in a thickness swelling of less than 10%.     

Effect of radiata pine juvenile wood on the physical and mechanical properties of oriented strandboard

This work analyzes the impact of radiata pine (Pinus radiata D. Don) juvenile wood on the physical and mechanical properties of oriented strandboards (OSB). Radiata pine logs were obtained from 10 trees of a 26-year old managed stand located in the 8th Region of Chile. The experimental design considered the proportion of juvenile wood and strand orientation as independent variables. OSB panels of 0.4 m×0.4 m×12 mm were produced and tested. The results show that the juvenile wood proportion has a significant impact on the physical and mechanical properties of OSB. Strands orientation had a significant impact on all the properties studied with the exception of the modulus of elasticity in bending. However, this impact was small in all cases and would not change panel grade with the exception of linear expansion. In this case, panels made from tangential strands showed a higher linear expansion. According to these results, radiata pine juvenile wood can be used for the manufacturing of OSB up to a proportion of 70% of the oven-dry wood weight without significant losses of the physical and mechanical properties if the juvenile wood strands are located in the surface layers.     

Biological properties of an OSB eco-product manufactured from a mixture of durable and non durable species and natural resins

OSB panels were manufactured with a mixture of pine and cypress heartwood and lignin and tannin based resins in order to propose an eco-friendly wood composite. The resistance of OSB panels against Reticulitermes santonensis was tested according to EN 118 and EN 117 as well as in a field test. OSB made from cypress showed more resistance against the tested termite, the resistance decreased as the percentage of pine increased. The degree of attack differed according to the choice of standard procedure. The field test results revealed that in outdoor conditions and when the termites had a feeding choice, all mixtures showed the same behaviour. The decay resistance was assessed according to EN 12038, and the results revealed that the resistance increases when the percentage of cypress increases.     

Some Properties of Composite Panels Manufactured from Eastern Redcedar (Juniperus virginiana L.) Using Modified Starch as a Green Binder

The objective of this study was to evaluate basic properties of particleboard panels manufactured from Eastern redcedar (Juniperus virginiana L.) using modified starch and low percent of urea formaldehyde as binder. Experimental panels in the form of three-layer configuration were made from the raw material at two density levels. Bending characteristics, namely, modulus of elasticity (MOE), modulus of rupture (MOR), and internal bond strength (IB) in addition to dimensional stability and surface roughness of the samples were determined. The highest MOE and MOR values of the samples with 0.80 g/cm³ density level were found as 2344.32 and 12.14 MPa, respectively. Both bending and IB values of the samples were comparable to those of commercially manufactured panels from other species. It appears that dimensional stability of the panels needs to be enhanced. Based on the findings in this work, modified starch could have potential as green binder in particleboard panels manufactured from Eastern redcedar without having substantial adverse influence on their properties.     

The effect of silicone on some properties of flakeboard

Waxes are used as water repellent in wood composites, and there are only limited alternative water-repellent systems for wood composites. The aim of this study was to investigate the effectiveness of a silicone compound as a water repellent for flakeboard and to compare the properties of boards made with silicone treated flakes to those made with commercial wax treated flakes. Three levels of silicone and wax application rates were used (0.25, 0.5, and 1%). The hydrophobic nature of silicone-treated flakes was evaluated by measuring the contact angle and the rate of water absorption (WA) on the surface of the wood flake. The internal bonding strength (IB), the modulus of elasticity (MOE) and modulus of rupture (MOR) in bending regime, the WA, and the thickness swelling at edges of boards were evaluated. Results obtained showed that IB, MOE and MOR decreased as the concentration of silicone on the flakes increased from 0.25% to 1%. The IB, MOE and MOR of panels made with 0.25% silicone-treated flakes were comparable to boards made with 1% wax-treated flakes. Thickness swell at edges and WA were significantly reduced as the amount of silicone increased. No significant difference was found for the thickness swelling at edges and the WA between panels made with 1% silicone-treated flakes and 1% wax-treated flakes. The silicone treated flakes had high water repellency.     

Mechanical behaviour of Québec wood species heat-treated using ThermoWood process

Finnish wood heat treatment technology, ThermoWood, was recently introduced to Québec, Canada by Ohlin Thermo Tech. Subsequently, a large number of initial trials were conducted on five commercially important Québec wood species, spruce (Picea spp.), pine (Pinus spp.), fir (Abies spp.), aspen (Populus spp.), and birch (Betula spp.). These species were thermally-modified in different batches at temperatures of 200 °C or higher. The static bending and hardness of the thermally-modified wood were examined. Decreases of 0% to 49% were observed in modulus of rupture of heat-treated spruce, pine, fir, and aspen depending on species and treatment schedules used; modulus of rupture of birch increased slightly after the heat treatment. The decrease in modulus of elasticity of heat-treated spruce and pine ranged from 4% to 28%; but the modulus of elasticity of heat-treated fir, aspen, and birch increased except one trial for fir. Hardness of the heat-treated wood increased or decreased depending on the species, test directions (radial, tangential, and longitudinal), and treatment schedules.     

Effect of panel properties on the concentrated static load (CSL) performance of oriented strand board (OSB)

The relationship between concentrated static load (CSL) performance of oriented strand board (OSB) and panel thickness, local density, and some mechanical properties (including modulus of elasticity (MOE), modulus of rupture (MOR), and interlaminar shear strength in both major and minor directions) was investigated using both a simple linear regression method and a stepwise multi-linear regression technique. The sample boards were laboratory manufactured OSB panels consisting of eighteen combinations of different strand geometries (length, width, and thickness), strand orientations, and fines contents. Simple linear regression analysis showed that MOE (major direction), MOR (major direction), shear strength (major direction), local thickness, average board density and local density were all significantly and negatively correlated with the CSL deflection; however, in the stepwise multi-linear regression analysis only MOE (major) and local thickness were retained as significant factors possibly due to inter-correlation amongst the variables. Shear strength (major direction), MOR (major direction), average board density, MOE (major direction), MOR (minor direction), local thickness, average board thickness, local density, and shear strength (minor direction) were all found to be significantly and positively correlated with the CSL ultimate load in the simple regression analyses, but only shear strength (major) and local panel thickness were retained in the stepwise multi-linear regression model for the CSL ultimate load.     

Hydrothermal treatment of strand particles of pine for the improvement of OSB panels

The aim of this study was to evaluate the effect of hydrothermal treatment in strand particles of pine used for oriented strand boards (OSB) production. Strand particles of pine were hydrothermally treated at 130, 150 and 170 °C for 7 and 21 min, for the determination of chemical composition, pH, equilibrium moisture content, particles mass loss, and contact angle of these particles with phenol–formaldehyde resin. Afterwards, OSB panels were produced using 8% phenol–formaldehyde resin, with a nominal density of 0.7 g/cm³, and pressing cycle at 170 °C and 3.14 MPa for 8 min. Then, the panels were kept in climate chamber until mass stabilization for the determination of their physical and mechanical properties, and for comparison with the European standards. The hydrothermal treatment in the particles decreased carbohydrate, especially mannan, xylan and arabinans, resulting in reduced equilibrium moisture content, pH, and contact angle, and increasing buffer capacity and mass loss. In OSB panels, treated particles caused the drop in the equilibrium moisture content and reduction of the thickness swelling of the panel, without reducing the mechanical strength, making the hydrothermal treatment very attractive. The hydrothermal treatment at 170 °C for 7 min allowed the resulting OSB panel being classified into the categories 1 and 2 of the European standard, expanding its range of use.     

Effect of short-term thermomechanical densification of wood veneers on the properties of birch plywood

In this study, the physical and mechanical properties of plywood panels made from pre-compressed birch (Betula verrucosa Ehrh.) veneer were evaluated. Veneer sheets underwent short-term thermo-mechanical (STTM) compression at temperatures of 150 or 180 °C and at pressures of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 or 3.5 MPa for a period of 1 min prior to adhesive being applied and pressed into panels using phenol formaldehyde adhesive at 100 g/m² spread rate; this was one-third less than the adhesive spread used for the control panels (150 g/m²). The pressing pressure was 1.0 MPa, which was almost half of the pressure used for the control panels (1.8 MPa); and pressing time was 3 min, also half of the pressing time used for the control panels (6 min). The results showed that surface roughness of compressed veneer, water absorption and thickness swelling of plywood panels made from compressed veneer were significantly improved. The shear strength values of plywood panels made from compressed birch veneer even with reduced adhesive spread were higher than those of plywood panels made from uncompressed veneer. The findings in this study indicated that compression of birch veneer could be considered as an alternative to produce more eco-friendly (owing to smaller adhesive spread) value-added material with enhanced properties.     

Effects of MDI content on properties of thermally treated oriented strand board (OSB)

The paper discusses the influence of methylene diphenyl diisocyanate (MDI) content on mechanical properties of thermally post-treated single-layered oriented strand boards (OSB). The OSB differed in adhesive content (3, 4 and 5%) and the high temperature (HT) level of the thermal modification (TM) (untreated, 160, 175 °C). To characterise the mechanical behaviour of the OSB, the modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond (IB) of dry and boiled specimens were determined. In addition, the adsorption and desorption isotherms were investigated. The hygroscopic sorption isotherms were calculated according to the Hailwood-Horrobin equation. It was observed that the MOR and the IB of the post-treated OSB are significantly increased with higher MDI content. An increase of the MDI content from 3% up to 5% is not sufficient to compensate the loss of strength caused by TM. However, an increase of MDI-content of about 1% compensates the significant loss of IB of dry and boiled specimens. The MOE is not influenced by TM. With increased adhesive content, thermally treated and untreated specimens show slightly higher values. The thermal post-treatment of OSB alters the wood-water-interaction. The hygroscopicity is reduced. The higher the HT level, the lower is the sorption behaviour. It was also detected that a higher MDI content does not influence the hygroscopicity.     

Estimation of physical and mechanical properties of agro-based particleboards by near infrared spectroscopy

Partial least square regression (PLS-R) calibrations based on near infrared (NIR) spectroscopic data were developed in order to predict mechanical and physical properties of agro-based particleboards. The panels were manufactured using Eucalyptus and Pinus wood particles and sugar cane bagasse. The following panel properties were evaluated according to standard methods: modulus of elasticity (MOE), modulus of rupture (MOR), internal bonding (IB) strength, water absorption (WA24H), and thickness swelling (TS24H) after 24 hours of immersion. NIR spectra information was measured on samples cut from each particleboard and correlated with their physical and mechanical properties by PLS-R to build predictive NIR models. The NIR models for IB, WA24H and TS24H presented satisfactory coefficient of determination (0.73; 0.72 and 0.75, respectively.) The key role of resins (adhesives), cellulose, and lignin for NIRS calibrations of mechanical and physical properties of the particleboards is shown. These models can be useful to quickly verify such properties in unknown agro-based particleboards.     

Physical and mechanical properties of plywood produced with 1.3-dimethylol-4.5-dihydroxyethyleneurea (DMDHEU)-modified veneers of Betula sp. and Fagus sylvatica

The dimensional stability and some mechanical properties were tested in plywood produced with veneers modified with 1.3-dimethylol-4.5-dihydroxyethyleneurea (DMDHEU). The experimental design included Betula sp. and Fagus sylvatica impregnated with 0.8 M, 1.3 M, and 2.3 M DMDHEU. The plywood consisted of five veneers glued with a phenolic resin. Dimensional stability tests were conducted after 10 cycles of soaking/oven-drying to determine volume changes and anti swelling efficiency (ASE). The mechanical properties tested were hardness (Brinell), modulus of elasticity in bending (MOE), bending strength (BS) and work to maximum load in bending (WMLB). The modified samples for both species were considerably more dimensionally stable than the untreated samples. The samples of Betula sp. and F. sylvatica modified with DMDHEU presented a MOE and a BS unaffected by the treatment. The WMLB was consistently lower in the modified samples than in the unmodified samples. As determined by the Brinell method, the DMDHEU-modified plywood of the Betula sp. and F. sylvatica was harder than the unmodified plywood.     

Utilization of bark flours as additive in plywood manufacturing

Increasing demand for wood based panel products and shortage of wood as raw material have triggered many efforts to utilize residues generated annually by the forest industries including a large portion of bark in panel production. In this study, the effects of using bark flours as additives obtained from different wood species (walnut, chestnut, fir and spruce), having much polyphenol content, on some physical and mechanical properties and formaldehyde emission of plywood panels were examined. Wheat flour, which has been used widely as additive in plywood manufacturing, served as control. Plane tree (Platanus orientalis) logs were obtained for veneer manufacturing. Urea formaldehyde (UF) resin with 55 % solids content was used as adhesive. The bonding shear strength, bending strength, modulus of elasticity (MOE), density, equilibrium moisture content and formaldehyde emission of plywood panels were determined according to related standards. It was found that the use of flours obtained from the barks of chestnut and fir trees in the glue mixture decreased the formaldehyde emission of panels. The bonding strength values of the test panels made using the glue mixture including the flour of walnut and spruce barks as additive were lower than those of the panels with adhesive containing the flour of fir and chestnut barks. The panels manufactured with adhesives including the flour of fir bark gave the highest bending strength and modulus of elasticity values.     

Contact thermal post-treatment of oriented strandboard to improve dimensional stability: A preliminary study

The oriented strandboard (OSB) has less dimensional stability than plywood, but they are competitive panels and have been used for similar ends. The wood-water relation variables, such as thickness swelling and water absorption, express this OSB dimensional instability and can be explained by two main factors: wood hygroscopicity and imposed hot-pressing stresses. The objective of this present paper was to propose a thermal post-treatment as a method to improve OSB dimensional stability by decreasing wood hygroscopicity and releasing hot-pressing stress. OSB panels from Pinus taedawood were produced in laboratory, and their characteristics were: single layer, 0.8 g/cm³; 8% phenolic resin and without wax. The OSB panels were treated in a laboratory press at 250 °C for about 4, 7 and 10 minutes. The wood-water relation variables, thickness swelling (TS), water absorption (WA), equilibrium moisture content (EMC) and springback or permanent thickness swelling (PTS) were determined and compared with untreated panels. The results showed that the proposed thermal treatment was effective to reduce TS, EMC and PTS, but didn’t affect WA which was affected by panel density reduction. The longer the treatment the higher the dimensional stability, and panel weight loss could be used as predictive variable for the efficiency of the treatment.     

Untersuchungen zur Anwendung von Schaumharzleimflotten in der OSB-Technik

Investigations on application of foamed glue materials for OSB were made to get information about utilisation of this technology in the production of oriented panel board. By using aminoplast foamed gluelines the rate of thickness swelling could be reduced about 50%. The IB was sufficient in a rate of 0,8 N/mm². Unsatisfying at this stage is the bending strength. Here is more research work be necessary to look for optimising the extender materials.     

Properties of oriented strandboard made of wood species from Brazilian planted forests: Part 1: 80 mm-long strands of Pinus taeda L.

This research is part of a general study on the properties of oriented strandboard (OSB) using wood strands of species from Brazilian planted forests. The OSB industry is the latest wood related activity established in Brazil. In this particular part of the study, 80 mm long strands of Pinus taeda L. were bonded using two resin types (urea-formaldehyde and phenol-formaldehyde) at two levels of resin content (5% and 8%) to produce three-layer cross-aligned OSB to a face to core layer ratio of 1:2 and target density of 0.75 g/cm³. Physical and mechanical properties of the boards were evaluated according to ASTM standard D 1037-96a (1997) and the results compared to standards available as requirements for commercial structural panels. The results indicate that all the mechanical properties evaluated were above the requirements set forth by the Canadian standard CSA O437.0 (1993) for structural panels. The results of Janka hardness were in average 4 folds higher than the minimal requirements for Grade R-1 waferboard. Screw withdrawal values were also above the minimum required by grade M-3 of ANSI A208.1 standard (1993). Nevertheless, values of thickness swelling and water absorption were very high. The low dimensional stability may be related to the high density of the boards (“springback” effect) and also to the fact that no wax was used.     

Mitteldichte Faserplatten (MDF) aus gebrauchten Oriented Strandboard (OSB)

Zusammenfassung Die Ergebnisse zeigen, dass durch den alkalischen Aufschluss von Oriented Strand Boards (OSB), die in den Mittelschichten PMDI und in den Deckschichen MUPF als Bindemittel enthalten, Fasern gewonnen werden, die bei der MDF-Herstellung zur Verringerung der Dickenquellung und zur Erhöhung der Querzugfestigkeit führen. Die Biegefestigkeit der MDF nahm bei Zusatz von 25% OSB-Recyclingfasern kaum ab. Erst bei einer Ersatzmenge von 50% verringerte sich die Biegefestigkeit von ca. 60 N/mm² auf rund 50 N/mm².

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Medium density fibre boards (MDF) from recovered oriented strand boards (OSB)

Fibres for medium density fibre boards (MDF) were made from oriented strand boards (OSB) bonded with PMDI in the core and MUPF in the surface. Chips from OSB were pulped with sodium hydroxide. The fibres obtained therefrom were used for partial substitution of fresh fibres in MDF. The preliminary results reveal that recycled fibres decrease the thickness swelling enormously and has also a remarkable positive effect on the internal bond strength as well. However, the use of higher amounts (50%) of recycled fibres negatively impacts the bending strength.

     

Optimising the properties of OSB by a one-step heat pre-treatment process

Heat-treatment of solid wood to increase its dimensional stability and durability is well known and established in the industry. To enhance the application of wood-based panels (e.g. for exterior application) their durability against moisture and fungal decay has to be improved. In this paper a possibility is shown, how to adapt a heat treatment process on wood-based panels. Two different temperatures were applied on strands of Scots pine, before hot-pressing oriented strand board. The mechanical properties show an influence of the applied temperature on the strands and of the adhesive used for the panel. The thickness swelling is reduced (Fig. 3), resulting in increased dimensional stability. The process temperature has a major influence; with an increased pre-treatment temperature the thickness swelling is reduced. The internal bond strength was not affected by the pre-treatment.