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.     

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.     

Flat pressed wood plastic composites made of milled foam core particleboard residues

Flat pressed wood plastic composites were produced on a laboratory-scale using residues of lightweight foam core particleboards as raw material. Raw material preparation methods (dry blending and compounding with a twin screw extruder) and the wood flour content (WF) loading, as influencing parameters on the panel properties, were varied, and coupling agents (CA) were added in some variations. The results showed that panels produced with lower WF content (75 %) have better physical and mechanical properties compared to those of higher WF. The CAs only influenced the panel properties when they were added during the compounding of the materials. Due to the assumed higher wood degradation resulting from raw material compounding, the panel properties were inferior to the panels produced with dry blended materials.     

Influence of face-to-core layer ratio and core layer resin content on the properties of density-decreased particleboards

As a response to increased costs and a shortage in wood supply it is a current approach to reduce the amount of material in the manufacturing process of particleboard (PB). However, the production of lightweight PB by simply reducing density results in decreased panel properties. Thus, investigations to re-engineer the panel’s core layer are required in order to achieve density-reduced panels which meet minimum property requirements (e.g., EN 312), edge processability and surface coatability. The intention of the present paper is to investigate the influence of potentially occurring changes in the face-to-core layer ratio (35/65…57/43) and core layer resin content (8 %…22.3 %) on panel properties when reducing the density from 650 to 400 kg/m³.     

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.     

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.     

Real-time process modeling of particleboard manufacture using variable selection and regression methods ensemble

This study focuses on the real-time prediction of mechanical properties such as internal bond strength (IB) and modulus of rupture (MOR) for a wood composite panels manufacturing process. As wood composite panel plants periodically test their products, a real time data fusion application was developed to align laboratory mechanical test results and their corresponding process data. Fused data were employed to build regression models that yield real-time predicted mechanical property values when new process data become available. The modeling algorithm core uses genetic algorithm to preselect a meaningful subset of process variables. Calibration models are then built using several regression methods: multiple linear regression, ridge regression, neural networks, and partial least squares regression (PLS). Four different predicted response values were generated for each new record of real time process variables. On-line validation results showed good performance of the ridge regression method with a 0.89 correlation coefficient between actual and predicted MOR values, a root mean square error (RMSEP) of 1.05 MPa and a mean normalized error of 9 %. IB was best predicted by PLS with a 0.81 correlation coefficient between actual IB and PLS predicted IB values, a RMSEP of 75.1 kPa, and a mean normalized error of 15 %.     

Morphology of the Bagasse Fibers Obtained from the Elaboration Process of Mezcal and Effects on Their Tensile Properties

The morphology of the cross-section and longitudinal-section of bagasse fibers of Agave angustifolia Haw from the elaboration process of mezcal were investigated and tensile tests were performed in function of the diameter (0.20–0.79 mm), gauge length (10, 15 and 20 mm) and strain rate (5–50 mm/min). The cross-section of the fibers is ribbon-shape like with dislocations and the longitudinal section has mechanical damage in its surface. The ultimate tensile strength (14.83–86.51 MPa) and Young’s modulus (0.20–1.26 GPa) are influenced by the diameter and the strain rate, while the strain at failure (16–26%) is influenced by the gauge length. These results are discussed in light of information on relationship between morphology and tensile properties of natural fibers and possible effects of the elaboration process of mezcal.     

Influence of different wood flour fractions on the mechanical properties of injection molded WPC with cellulose propionate

This research investigated the effect of different fractions of commercial wood flour (Type c100 from JRS, Germany) on mechanical and physical properties of wood-polymer composites (WPC). The fractions were named regarding the mean lengths of their particles in µm; 80, 130, 255, 405 and 485. The composite samples were manufactured with 30 wt% of wood flour fractions of all five groups as well as the not fractionated flour, and 70 wt% of cellulose propionate (CP). The melt mass-flow rate (MFR) of the different granules, tensile strength, and modulus of elasticity, flexural strength, flexural modulus and the impact strength of the injection molded specimens as well as the water uptake were determined in this study. WPCs with the specific size range used in this investigation exhibited improved strength and modulus of elasticity in tensile and flexural tests, compared to pure CP. Using fraction 255, the mechanical properties increased the most. Tensile strength rose by 28 and 13% compared to CP and to WPC with the not fractioned wood powder, respectively. Fraction 255 increased flexural strength by 33 and 5% compared to CP and WPC with the not fractioned flour. The MFR (tested at 190 °C with 7.16 kg) of WPC_255 is the lowest with 2.3 g/10 min. Composites with the smallest particles showed the least water uptake.     

Zerstörungsfreie Bestimmung elastischer Eigenschaften quadratischer 3-schichtiger Brettsperrholzplatten mit symmetrischem Aufbau

Some of the most important material properties of engineered wood products, like cross-laminated solid wood panels, are the elastic properties. Regarding panels, the two in plane MOEs (E_ii) and three shear moduli (G_ij) are of particular interest. In order to determine these parameters with an economically and non-destructive technique, a method was developed which allows to determine all five parameters in one experiment only. This method was approved on 24 square-shaped cross-laminated solid wood panels with side-length of 2.5 m, thickness of 70 mm and two different layer sizes. The panels were produced by two plants applying different technologies. The determined elastic parameters were verified by bending tests and compared with stiffness parameters calculated on basis of the elastic compound theory. Four elastic parameters could be determined and proven to be correct. The results did neither depend on the different production technologies of the panels nor on the two different compositions of layers. The determinability of the elastic parameter G₂₃ depends on the geometry of the panels. Noteworthy is the fact that stiffness parameters calculated assuming that the raw material of the single layers corresponds to strength class C24, can be on the ‘‘unsafe side’’.     

Analysing orthotropy in the core layer of wood based panels by means of fracture mechanics

In this study the orthotropic properties in the core layer of wood based panels are analyzed by means of the newly developed double cantilever I beam testing system. Four different wood based panels (i.e., OSB, particle board, particle board containing recycling chips and MDF) were tested in-plane, in longitudinal and lateral orientation. Specific fracture energy numbers yielded significant differences between the longitudinal and the lateral orientation for OSB, while the stress intensity factor analysis showed significant differences for OSB and particle board containing recycling particles.     

Thickness swelling and water absorption of WPC after immersion in cold and boiling water

Thickness swelling (TS), water absorption (WA) and edge swelling (ES) of 20 mm flat-pressed wood–plastic composites (WPC) panels with a wood flour (WF) content of 50 and 70 % manufactured using an industrial single-daylight press and samples of a high pressure laminate (HPL) compact panel were determined after immersion in cold water according to EN 317 and boiling water according to EN 438 in order to propose, describe and verify a method to (1) measure TS, WA and ES more quickly than by applying EN 317 and (2) to make the properties of WPC and HPL comparable to each other. TS, WA and ES of WPC panels determined after immersion in cold and boiling water were found to correlate with a correlation coefficient of 95–99 % equating 24 h (EN 317) and 0.5 h (EN 438) to factor x. Properties of WPC panels with WF content of 50 % were found to be comparable, respectively superior to those of HPL.     

Effect of industrial wood particle size on mechanical properties of?wood-polyvinyl chloride composites

Wood-polyvinyl chloride (PVC) composites were prepared using industrial wood particles used for manufacturing three-layer particleboards. The effect of particle size (0.25–0.5, 0.5–1, 1–2, and 2–4?mm) on the mechanical properties of the composites was investigated. The effect of cross-section size (4×10, 6×15 and 8×20?mm²) of composite pieces made by an injection moulding method was also studied. Both the particle size and specimen cross-section area significantly influenced these properties. The tensile and flexural properties as well as the impact strength in general increased with increasing particle size, and decreased with increasing cross-section size.     

Experimental determination of the compression resistance of differently shaped wood particles as influencing parameter on wood-reduced particleboard manufacturing

The price for industrial wood and, thus, particles for the manufacture of particleboard has been rising in the past and will be a topic of current interest in the future as economic growth is targeted at limited resources. One of the strategies to overcome this development is to reduce the amount of wood used for panel production. However, a simple reduction in the amount of wood used for panel manufacture leads to panels of lower density and, consequently, reduced properties. One approach to solving this problem is to re-engineer the particle mat structure to improve the panels’ density profile and, thus, meet required panel properties and at the same time lower board densities. As the particles’ compressibility is one of the main influencing parameters for density profile formation, it is the intention of this study to use a previously developed measurement method to give compression resistances of particles of various shapes and dimensions. It was found that the bulk density alone is not decisive for the particles’ compression resistance. The compression resistance derived from the change of particle shape is lower than that derived from wood substance compression. The compression resistance of large-sized particles was found to be higher than that of small-sized particles. It was concluded that a targeted combination of face and core layer particles improves the panels’ density profile.     

Fire performances of foam core particleboards continuously produced in a one-step process

For further progress of novel foam core particleboards, their fire performance was examined with cone calorimetry tests (ASTM E 1354-11a). Specimens with varying surface layer thicknesses, foam densities (polystyrene foam), and processing temperatures were tested. Using the initially recommended cone irradiance of 35 kW/m², different flammability parameters were measured. In comparison to particleboards, the foam core panels generally had much higher heat release rates, somewhat higher heat of combustion and much higher smoke production due to the EPS-foam component of tested panels. The time to ignition and total heat release did not vary significantly among the samples, although certain trends could be explained. The effects of variations in specimen foam densities and processing temperatures on the flammability parameters were not very significant. However, the flammability properties improved towards that of the reference particleboard as the surface layer thickness increased from 3 to 5 mm.     

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.     

Investigation of mechanical properties of sandwich panels made of paper honeycomb core and wood composite skins by experimental testing and finite element (FE) modelling methods

In this study, lightweight sandwich panels with different Kraft paper honeycomb core structures and wood composite skins were constructed. The influence of structural parameters, including core shape, cell size, core density, core and web thickness, and material properties of the core and skin layers on the mechanical behavior of these lightweight sandwich panels were studied by experimental testing and finite element modeling methods. The panels were subjected to compression and shear loadings. Test and simulation results indicated that core density and core shape mainly affected the panel stiffness under out-of-plane loading conditions (e.g. E _z , G _xz and G _yz ). Material properties of the skin layer affected the panel stiffness both under in-plane and out-of-plane loadings if the skin layer was orthotropic.     

Improving physical and mechanical properties of new lignin- urea-glyoxal resin by nanoclay

To eliminate toxic formaldehyde from wood based panels, glyoxal, a low volatility and nontoxic aldehyde, was used to react with urea and lignin to prepare a glyoxalated lignin- urea-glyoxal (LUG) wood adhesive resin. Moreover, another objective of this research work was to improve the physical and mechanical properties of the new LUG resins by nanoclay addition. For the preparation of LUG resin, glyoxalated lignin (15 mass%) was added instead of second urea to the urea-glyoxal resin synthesis under acid conditions. The LUG resin so prepared was mixed with 1, 2 and 3 mass% nanoclay by mechanically stirring for 5 min at room temperature. Then, the physicochemical and structural properties of the prepared resins as well as the water absorption and the mechanical properties of the plywood panels bonded with it were measured according to standard methods. The physicochemical test results indicated that the gel time of the LUG resin was markedly slower than that of the UF resin. Plywood panels prepared with the LUG resin also presented lower water absorption as well as weaker shear strength than those prepared with the UF resin. Addition of nanoclay changed the physicochemical properties of the resins as the gelation time of the LUG resin was shorter when adding sodium montmorillonite (NaMMT). Higher shear strength values and lower water absorption were achieved by continuously increasing nanoclay proportion from 1 to 3 mass%. Furthermore, addition of nanoclay had more influence on panels bending strength than their flexural modulus. X-ray diffraction (XRD) analysis also indicated that NaMMT exfoliated completely when mixed with LUG resin.     

Effects of Wood Particle Size and Mixing Ratios of HDPE on the Properties of the Composites

The main goal of this research is to innovate wood-plastic composites by using various wood particle sizes and different mixture ratios (weight ratio) of HDPE (High Density Polyethylene). After mixing the wood particles (recycled wood waste) and the plastic powder, we use a molding and pressing process to make composites with a thickness of 12 mm. By doing so, the wood particle content can be increased to 75%. This kind of composite provides excellent dimensional stability, its moisture content is under 2.5%, and the thickness swelling rate after 24 hr water absorption is under 7.5%. The maximum static bending strength of this composite reaches 20.7 N/mm², and is better than that of general commercial particleboards. The composite made of larger sized wood particles has better strength properties. In addition, when the plastic content ratio increases, the dimensional stability of the composite will increase as well. After the soaking process in boiling water, the static bending strength of wet composite remained at 50%; this shows the good weather resistance of the composite. The surface veneer overlaid peeling strength of the composite showed 1.02–1.63 N/mm. After the evaluation of processing, cost of material and strength properties of the composite, we would suggest that the use of 70% of wood particles and 30% of plastic powder is practical to produce proper sized composites.     

Carbonization of hot-pressed ARBOFORM ®-mixtures

Porous carbon materials have a wide range of technical applications due to their properties including low density potential, mechanical capacity, resistance to heat and corrosion as well as electric conductivity. Organic materials like phenolic resins or polyacrylnitrile are typically employed as green body for carbon ceramics. However, wood and especially wood-based composites are also suitable as well as hot-pressed ARBOFORM^®-powder mixtures from lignin, wood meal and natural additives, which varied with regard to their lignin content as well as partly regarding their additive rates. The objective of the present study was to investigate the influence of some admixed additives of a commercially available wood based composite on carbonization results. The experiment was performed due to its more homogenous material properties in comparison to solid wood. Another aspect was the possibility of forming mixtures of ARBOFORM^® by extrusion or injection moulding. Such production processes are already state of the technology and therefore it could be possible to produce complex carbon- and ceramic templates which are difficult to realize by conventional processing methods. Concerning the thermoplastic process step of ARBOFORM^® there are further advantages compared with the used wood based panels. The samples were pyrolyzed in a nitrogen atmosphere at a temperature of up to 900 °C. Regarding the absence of cracks, best results were achieved with blend P60 which had a higher content of wood particles. Addition of only 10% of phenolic resin significantly counteracted density reduction.