Characterization of properties of oriented strand boards from beech and poplar

The aim of this study was to evaluate the possibility of using European beech and poplar species to manufacture oriented strand boards (OSB). Beech and poplar strands with three different combinations of face/core ratios at densities of 650 and 720 kg/m³ were examined. Poly methylene diphenyl diisocyanate glue at 5 % was used with press conditions of 180 °C and 240 s. Findings showed that with increasing density the physical and mechanical properties of the different OSB combinations generally improved. Panels made of 60 % beech in face layers showed higher modulus of rupture and modulus of elasticity. Internal bond strength rose as the amount of beech strands in the core layer increased. Panels with 75 % beech strands in the core layer showed the maximum internal bond strength at 720 kg/m³. It was also observed that increasing the amount of beech in the core layer from 40 to 75 % decreased thickness swelling at both densities.     

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%.     

Tailor made OSB for special application

The purpose of this study was to develop speciality oriented strand board (OSB) with high stiffness for use in products such as engineered wood flooring (EWF). Three-layer oriented strand boards were manufactured from two feedstocks of strands: a mixture of 90% aspen (Populus tremuloides) and 10% of paper birch (Betula papyrifera), and 100% of small diameter ponderosa pine logs (Pinus ponderosa). The OSB panels were manufactured under a factorial design of three resin contents, two density profiles, and three weight ratios for the face and core layers. Tests to determine density, bending modulus of elasticity (MOE), internal bond (IB) and thickness swelling (TS) were performed according to ASTM standard D 1037-06a. The results showed that the higher values of bending MOE for panels made from aspen/birch mixture and ponderosa pine, 8190 and 9050?MPa, respectively, were obtained for the same combination of factors. Such high bending MOE values are very close to Baltic birch (Betula pendula) plywood, a product known for its high stiffness. The effect of resin content on IB is more pronounced for panels made from ponderosa pine than panels made from the aspen/birch mixture. Thickness swelling of panels made from ponderosa pine strands is higher than thickness swelling of panels made from a mixture of aspen and birch strands. The results indicate the potential to tailor an OSB for a specific application such as EWF.     

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.     

Effect of relative humidity on some physical and mechanical properties of different types of fibreboard

Equilibrium moisture content and strength properties as a function of relative humidity (RH) were measured in three types of commercial fibreboards with different densities. The measurements were made after specimens had been conditioned to equilibrium at 35, 50, 65, 80 and 95% RH and 20 °C. It was shown that the modulus of elasticity decreased slightly between 35 and 65% RH and markedly – at above 65% RH for all types of boards. A very strong decrease of modulus of elasticity was observed at about 80% RH (capillary condensation). A similar decreasing trend was observed in bending strength. Overall, high RH had a noticeably detrimental effect both on the MOE and the bending strength for all tested boards. Adequate correlation exists between bending MOE and bending strength with moisture content. The lower the density of boards the higher their equilibrium moisture content.     

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.     

Potential of pulp and paper secondary sludge as co-adhesive and formaldehyde scavenger for particleboard manufacturing

This study investigated the potential of secondary sludge (SS) as urea–formaldehyde (UF) co-adhesive for particleboard manufacturing. Three proportions of SS from three conventional pulping processes were added in the formulation of particleboard manufacturing. A 3³ factorial design was used. All panels were tested for thickness swell (TS), linear expansion (LE), internal bond strength (IB), flexural modulus of elasticity (MOE), flexural modulus of rupture (MOR) and formaldehyde emission. Results indicated that particleboards made with SS from thermomechanical pulp (TMP) and kraft pulp (Kraft) met the ANSI standards for LE, IB, MOE, and MOR (with 7 and 9 % UF). However, the TS of panels made with SS was higher than that of control panels and adding SS to the formulation affected negatively this property. Most of the properties studied in the particleboards made with SS from chemical–thermomechanical pulping (CTMP) process failed to meet the ANSI standards. The main advantage of using SS as co-adhesive is the reduction of formaldehyde emission, in the best case here, about 50 %, with CTMP sludge added, of the particleboards.     

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.     

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.     

Properties of one-layer experimental particleboards from willow (Salix viminalis) and industrial wood particles

The objective of this study was to investigate some mechanical and physical properties of one-layer particleboards made from various willow (Salix viminalis) and industrial pine wood particle mixtures bonded with urea formaldehyde resin. Modulus of elasticity and modulus of rupture decreased, whereas internal bond and screw holding strengths increased with increasing willow particle content. The decrease in bending properties was rather small; these properties of particleboards containing 50 % willow particles were on average smaller by about 10 % than particleboards containing only industrial wood particles. Increasing the willow particle content resulted in improved water absorption and thickness swelling. The willow Salix viminalis can be considered as a substitute for pine wood for manufacturing of particleboards.     

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.     

Paricá (Schizolobium amazonicum) and embaúba (Cecropia sp.) as new raw materials for particleboards

In this work two potential new species for forest plantation projects in Northern Brazil were evaluated for their suitability in particleboard production. The main evaluated parameters of the laboratory boards were pH value and buffer capacity of the particles, compaction ratio, thickness swelling, modulus of elasticity (MOE), modulus of rupture (MOR) and internal bond (IB). The results showed that both species are highly suitable for particleboard production as they presented low densities (400–430 kg/m³), light color, good compressibility and no apparent adverse reactions after UF-resination.     

Investigation of physical and mechanical properties of oil palm wood core sandwich panels overlaid with a rubberwood veneer face

Low-density sandwich panels consisting of an oil palm wood core overlaid with a rubberwood veneer face were manufactured. Effects of two types of grain orientation of the oil palm wood core (parallel and perpendicular to board surface) and three different veneer thicknesses (0.7, 1.8 and 2.7 mm) and core densities (223 ± 14, 301 ± 35 and 418 ± 33 kg/m³) on some physical and mechanical properties of the boards were investigated. Results showed that higher core density increased the values of thermal conductivity, screw withdrawal resistance, modulus of rupture and modulus of elasticity but decreased the value of water absorption without effect on thickness swelling of the boards. Boards with the core grain direction oriented perpendicular to panel’s surface possessed lower value of thickness swelling but higher values of thermal conductivity and strain at fracture when the board failed in a mode of core shear under bending test than those of the others. Finally, the relationship between board density and the measured physical and mechanical properties of the oil palm wood core sandwich panels overlaid with a rubberwood veneer expressed as mathematical equations could be used to predict and design the expected properties of this type of sandwich board.     

Influence of hydrothermal modification of fibers on some physical and mechanical properties of medium density fiberboard (MDF)

Any treatment of fibers can influence properties of medium density fibreboard (MDF). In this research, the effects of hydrothermal treatment on physical and mechanical properties of MDF were studied. Industrial fibers were hydrothermally treated in a stainless steel reactor at 120, 150 and 180 °C for 0, 30 and 90 min as holding time. Test boards were made based on 0.7 g/cm³ target density, with 10 mm thickness under a pressure of 30 bar and at a temperature of 170 °C and a press time of 10 min. The boards were tested for internal bonding (IB), moduli of elasticity (MOE) and rupture (MOR), thickness swelling and water absorption. Results showed that the water absorption was not affected by the hydrothermal treatment; while the thickness swelling was improved and the boards became dimensionally stable. The MOE was slightly reduced due to the hydrothermal treatment. The MOR and the IB were significantly decreased by the hydrothermal treatment.     

Particleboards production from date palm biomass

Date palm biomass is a renewable natural resource that has not widely been utilized in industry. The objective of this study was to examine some chemical properties of date palm trunk and rachis (holocellulose, cellulose, lignin and extractives) and to evaluate their suitability to produce composite panels. Particleboards were produced using trunk and rachis as an alternative raw material for forest products industry in the presence of two types of polycondensation resins (phenol–formaldehyde and melamine urea–formaldehyde) which were selected as binding agents. The panels were tested for their physical (water absorption and thickness swelling) and mechanical (modulus of rupture, modulus of elasticity and internal bond strength) properties. The internal bond strength of date palm trunk and date palm rachis based boards met the requirements of the general purpose product standards (EN 312) at 0.70 g/cm³ density. The panels made with phenol–formaldehyde resin showed better performance with respect to the panels made with melamine urea–formaldehyde. In addition, the particleboard made with date palm trunk particles had better quality compared to the particleboard made from date palm rachis particles. Based on preliminary results of this work, raw materials from date palm trunks and rachis can have a promising potential in the manufacture of particleboards and as a substitute for wood in board production.     

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.     

Some investigations concerning density profile,internal bond and relating failure position of particleboard

Testing machines for the measurement of density profiles of wood based panels have become a wide-spread tool in production laboratories. New equipment for the in-line measurement of density profiles was presented recently. The high significance of the density profile for the properties of particleboard ticleboard is well known for some years. Maximum densities in the outer zones of the profile are closely related with MOE, bending strength, water uptake and swelling. Minimum density is closely related with shear modulus (G _(xz , (G _(yz ), shear strength and compression strength. However, results about the correlation of the minimum density with internal bond are contradictory, and statements concerning the failure positions relating to the internal bond-test are published rarely. For five different thicknesses of furniture grade particleboard the relation between internal bond, parameters derived from the density profile and the respective failure position were determined. Indeptendent of panel thickness the failure position was found to be in a range of the 25-75%-panel thickness. A correlation between the failure position and parameters derived from the density profile could not be found. There appear to be three predetermined failure lines (35, 50, 65% of panel thickness). The correlation between mean density and internal bond is high for the total sample (r=0.81). The correlation between minimum density and internal bond is lower, especially with regard to results relating to a single panel thickness.     

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.     

Density and some mechanical properties of densified and heat post-treated Uludağ fir,linden and black poplar woods

The effects of thermo-mechanical densification and heat post-treatment on air-dry density, modulus of elasticity (MOE), bending strength (MOR), and compression strength parallel to the grain (CS) of Uluda? fir (Abies bornmulleriana Mattf.), linden (Tiliagrandifolia Ehrh.), and black poplar (Populus nigra L.) wood samples were investigated. Samples were densified with compression ratios of 25 and 50%, and at 100 and 140?°C. Then, the heat treatment was applied to the samples at 185 and 212?°C for 2 h. According to the results of the study, density of all wood samples increased together with the increase of compression ratio. Regarding compression temperature, the highest density increase was obtained at 100?°C. Mechanical strength (MOE, MOR, and CS) in densified samples increased depending on compression ratio and increase of density. The highest strength increase was in black poplar samples and the lowest was in linden samples. After heat post-treatment, mechanical strength of samples decreased depending on increase in treatment temperature. However, strength values (MOR except) of samples which are 50% compressed and heat-treated were found higher than control samples.     

Untersuchungen zum Einfluss der Holzfeuchte auf ausgewählte Eigenschaften von Spanplatten und MDF

On industrially produced particle boards and MDF, the influence of wood moisture on bending MOE, bending strength and shear modulus G_zx and G_zy was determined. The equilibrium moisture content and the differential swelling of thickness proved to be smaller for MDF than for particle boards. Tensile strength and tensile MOE, shear modulus and bending strength decrease likewise with increasing wood moisture content. Furthermore the Poisson ratio μ₁₂ decreases with increasing wood moisture content.