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Ultra-lightweight foam-core fibreboard with 19 mm thickness was produced with a novel one-step process using resinated wood fibres for the faces and expandable polystyrene (EPS) as core layer material. The aim of the current study was to investigate the panel properties produced with different EPS bead diameter (0.5, 1.5, and 2.5 mm) and surface layer thickness (1, 2, 3, 4, and 5 mm). The EPS bead diameter showed a significant effect on the properties of foam-core fibreboard. The most uniform foam with the smallest cell size and highest cell density was observed in panels with smaller EPS beads, which also resulted in a remarkable increase in bending strength and edge screw withdrawal resistance (SWR) of the foam-core panels. Increasing the surface layer thickness from 1 to 5 mm significantly raised the foam-core panels’ density from 220 to 460 kg/m3, respectively. The higher the panel density, the higher the bending properties and the face SWR. The physical properties (thickness swelling and water absorption) of foam-core panels were negatively influenced by thickening of the surface layers. In general, foam-core fibreboards made with smaller EPS beads (0.5 mm) and 3 mm surface layers (density of 340 kg/m3) showed excellent potential for furniture manufacturing due to their acceptable properties according to EN622-5/P1 while still having nearly 55% lower density compared to conventional fibreboard density (750 kg/m3).

Geopolymer was used as a multifunctional mineral binder to produce laminated veneer lumber (LVL). The main aim of the study was to characterize the various geopolymer binder formulations based on natural kaolin, metakaolin and silica fume. The effect of different combinations of aluminosilicate powder in geopolymer binder was characterized via FTIR, XRD and TGA analysis. The mechanical (shear, bending, and compression) and physical (thickness swelling and water absorption) properties of the LVL specimens were also evaluated. Results showed that characteristic bands attributed to the geopolymer binder were more pronounced with further replacement of kaolin with metakaolin and silica fume. The higher the metakaolin content, the greater the amorphous content of the reaction products. The mechanical properties of the LVL samples strongly depended on the unreacted components (Si and Al molecules) existing in the aluminosilicate powder as well as the Si/Al ratio in geopolymer binders. The content of unreacted components was reduced by decreasing of the kaolin content in the binder formulations. Furthermore, increasing of Si/Al ratio, via addition of silica fume, showed positive influence on kaolin-based binders, while it showed a slightly negative influence on metakaolin-based binders. Although metakaolin is more favored for geopolymer synthesis due to its better mechanical, chemical, thermal and durability properties, the combination of kaolin with metakaolin could enhance its characteristics to be used as an aluminosilicate source for geopolymer binder. Kaolin-based binders showed higher tendency to penetrate into the wood cell lumens compared to metakaolin-based binders.

Special tubular fiberboard with a density of 550 kg/m3 was manufactured using the round rods for creation of the holes. Physicomechanical properties of tubular fiberboard (6, 8, 10, 12 (mm)) with various hole diameters and number of hole (0, 1, 2 and 3 in a constant cross section) were evaluated. The surface layers density, especially on top of the holes, considerably elevated with increasing the hole diameter. This did create higher bending properties as well as higher internal bond and surface soundness. The structure of webs between the holes, when the holes’ number increases, were predominant factor influencing the panel properties. Weak and loose web structure were obtained by increasing the holes’ number from 1 to 3 within a constant cross section (50 mm × 16 mm) that was due to the less transferred fiber during pressing in the webs’ sections. A corresponding comparison of panel properties with those in American and European standards presents that the minimum requirements according to most of the standards (ANSI A208/2, EN 14755, EN 312/P2 and EN 622-5/P1) were obtained.

The hybridisation of wood-based panels has gained interest in recent years. Lightweight hybrid panels consisting of wood fibres as faces and a mixture of wood particles with expandable polystyrene ...

Chitosan was used as environmentally friendly and bio-based scavenger for reducing the formaldehyde emission from medium density fiberboard. Using of chitosan powder showed better capacity of formaldehyde adsorption rather than the chitosan solution. Liquid 13C-NMR showed that the free formaldehyde in urea formaldehyde adhesive having chitosan powder was drastically reduced. Additionally, the observed peak at 155 ppm showed that that the chitosan powder was copolymerized with urea formaldehyde adhesive. Increasing the amount of chitosan powder was significantly reduced the emitted formaldehyde. It was shown that the formaldehyde adsorption of chitosan was strongly influenced by the pH value of adhesive composition. The pH value and the adhesive gel time tended to increase with addition of chitosan powder, due to the proton affinity of chitosan. The mechanical and physical properties of panels did not significantly change when the chitosan content as scavenger was raised up to 3%, while a formaldeh...

Low density hybrid panels (16 mm thickness) were produced using wood fiber as face layers and a mixture of coarse wood particles and expandable polystyrene (EPS) as core layer. The EPS was foamed (in-situ foaming) in the core layer during the pressing stage. The effects of granules diameter (0.4, 0.8, 1.15, 1.5, and 2.2 mm) and granules content (5, 10, and 15%) on the physical and mechanical properties were evaluated. The results showed that both variables had significantly influenced the panels’ properties. Mechanical properties mostly depended on the level of mechanical inter-locking of EPS with wood particles, while the physical properties were mostly influenced by the EPS distribution. Stronger mechanical inter-locking of EPS with wood particles was achieved by both larger diameter and higher amount of EPS granules (2.2 mm and 15%). A better EPS distribution between the wood particles was observed with the smaller EPS granules and higher amount of EPS (0.4 mm and 15%).

In this research, a new binder class for wood based composites, named geopolymer binder, was developed based on pozzolanic by-products (e.g. fly ash). Additionally, effects of different amounts of silica fume, as a replacement agent with other aluminosilicate components (e.g. fly ash and metakaolin), have been evaluated in the innovative binder. The Automated Bonding Evaluation System technique was used to characterize the bonding shear strength of the developed geopolymer binder. It was shown that the best shear strength for fly ash based binders was obtained by the lowest press temperature and longest pressing time. The addition of silica fume (from 20% up to 100%) significantly influenced the bonding shear strength in all binder types. Due to the chemical and mineralogical compositions, silica fume displays higher pozzolanic activity than metakaolin whereas fly ash shows lower strength in comparison to metakaolin. The silica fume (100%) based binder has also superior shear strength compared to those of conventional UF resin and other geopolymer binders. Bonding shear strength like that for UF resin was achieved by substituting only 20% silica fume in geopolymer binder compositions.

A simulated one-step process has been developed for the production of foam core particleboards using rigid polyurethane as the core layer. The results showed that the different techniques used for surface layer separation (unresinated particles and sprayed water) and foam injections (open system and closed system) had no influences on panels’ characteristics. Mechanical properties (e.g., bending strength and internal bond strength) were mostly influenced by the surface layer thickness, while the water absorption and edge screw withdrawal were influenced by the foam cell structure. The use of sprayed water for surface layer separation doubled the formaldehyde emission (FE) of the panels. The addition of urea (based on 10% of the dry resin) to the sprayed water had a positive effect of reducing the final FE. Furthermore, increasing the surface layer thickness had a positive, linear relationship with FE.

Increasing markets for internet traded furniture but also economic concerns are main driving forces to con siderably reduce the weight of wood based furniture panels. Recent research and technological developments have led to an innovative one step process which simplifies the typical multi step process for production of foam core panels. Three layered sandwich panels (with particleboard faces and polymeric in situ expanded foam as core layer) can be pro duced by a one step process without additional gluing between the face and core layers. As the morphology of the foam and hence its mechanical properties strongly depend on its chemical composition as well as on the process param eters during expansion there are no data available so far describing the foam of the novel panels. The aim of the proposed project is to determine the elastic properties of in situ expanded foams using 2D digital image correlation. The data can be used later on for the simulation of the elastic behavior of foam core particleboards by means of FEM to describe the short and long term behavior of the panels.

Transforming waste or recycled materials into value-added products is of high priority today. Wood plastic composites (WPCs) show high potential for the use of recycled materials in making durable composites. The applicability of WPC panels produced from recycled materials (ultralight foam core particleboards) for exterior building application was tested using wood-destroying basidiomycetes. The results showed that the panels were fully resistant against Coniophora puteana (Cp) and Gloeophyllum trabeum (Gt), but not very resistant against Pleurotus ostreatus (Po). The decay susceptibility index of Po-exposed specimens showed that the polystyrene-bonded (PS) samples were more resistant than solid beech wood samples that were used as references, followed by melamine-urea formaldehyde-bonded samples. A comparison with the reference samples also showed that the panel density had a significant influence on the panel’s resistance against basidiomycetes. The higher the panel density, the more resistance will be achieved in the panel.

Geopolymer binders are an emerging class of mineral polymer that can be manufactured from natural raw materials and industrial byproducts containing high amounts of silica (Si) and alumina (Al) in mineral compositions. Various ratios of materials used for manufacturing geopolymer binder have been tested to evaluate the bonding performance of geopolymers with wood by means of tests performed on an automated bonding evaluation system (ABES). Tests with a binder based on sodium silicate water glass (Na 50T) are partly promising, which resulted only 10% lower shear strength than that based on urea formaldehyde. The binder characteristics were significantly influenced by changing the ratio of SiO2:M2O (M=Na or K) and the ratio solid content to chemical base in the water glass. Expectedly, increasing press temperatures and pressing times showed a positive correlation with the curing performance of geopolymer binder. It was also demonstrated that the binder properties can be changed in wide ranges to obtain binders which fulfill the minimum requirements set by industrial users.

Chitosan and its derivatives (grafted chitosan and chitosan nanoparticles) were used as bio-based adsorbents in urea-formaldehyde (UF) resins, and accordingly, their effects on the curing behavior, resin structure, crystalline structure, and formaldehyde emission (FE) of final resin has been investigated. Synthesis of grafted chitosan and chitosan nanoparticles was confirmed by FTIR spectroscopy. Characteristics of UF resins were monitored by 13C NMR and X-ray diffraction. This analysis showed that the free formaldehyde and crystallinity of UF resin having chitosan-based adsorbents were substantially reduced. The FE was largely decreased in the medium density fiberboard (MDF) containing chitosan nanoparticles (60%), followed by grafted chitosan (34%) and chitosan powder (22%). A FE class of F**** (

Wood-based composites are widely used in consumer products, either in structural or non-structural applications. One of the basic elements for wood-based composites is the binder itself. Recent years have seen great development and trends in the field of eco-friendly binders in wood-based composite. There have been many concerns on the effects of formaldehyde and volatile organic compounds (VOC) released from wood-based products. Researchers have put lot of effort into developing environmental friendly products with enhanced sustainability. Binder materials with a focus on geopolymers (i.e., alumino-silicates) are discussed in this publication. The development and utilization of geopolymeric binders is relatively new in the field of wood-based composites. Up to the present there has been insufficient information regarding the manufacturing conditions and properties of wood-nonwood composite materials prepared using a geopolymeric binder. This paper considers the background of geopolymer materials and the possibilities of producing inorganic-bonded wood composite using geopolymer.

The effectiveness of treatments for the surface layer of novel foam core particleboards was evaluated by means of Cone calorimeter tests. Foam core particleboards with variations of surface layer treatment, adhesives, and surface layer thicknesses under similar processing conditions were used to produce the test specimen for the Cone calorimeter tests. Ignitability, heat release rate profile, peak of heat release rate, total heat released, effective heat of combustion, mass loss rate, gaseous emissions, and specific extinction area were measured using the cone irradiance of 50 kW m−2. Additional analysis of this data provided fuel composition information that could reveal the pyrolysis events of the composite boards. Thermocouples at various depths were used to provide further verification of pyrolysis events. The unprotected foam core panels generally had much higher heat release rates, somewhat higher heat of combustion and much higher smoke production due to the polymeric foam component of tested panels, whereas time to ignition and total heat release were not pronounced from the veneer treated boards. Adding the commercial fire retardant veneer to the face particleboard provided a dramatic improvement to the measured flammability properties. It worked sufficiently well with a 3 mm thick surface layer to improve the predicted flame spread rating of the foam core particleboards.

Weight reduction is becoming an important topic for the wood-based panels industry. Recent development for foam core particleboard in an integrated process has a great potential to replace heavy conventional particleboards. For further progress of these new types of panels, exploring the physical properties is of high interest. In this study, the effect of two different sets of process parameters (press temperature, pressing and foaming times) on the physical properties and dimensional stability of foam core panels was examined. Panels produced by a lower press temperature (130°C) have a better surface quality. Thickness swelling of panels in short- (2 h) and long-term (24 h, 14 days) immersion shows different trends due to the different attained foam structures. Small inter cellular voids between the foam cells formed during the in situ foaming process play an important role for the water absorption values, especially in short-term immersion. Different process parameters caused different fusion ...

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.

In the present paper, lightweight wood-based foam core panels were produced in a novel continuous process. Expandable microspheres (MS) and expandable polystyrene (EPS) were used as core materials. The influence of surface thickness and core materials on bending strength, internal bond and specific strength of the produced panel were investigated. With increasing the surface thickness, bending strength was increased in both core types of panels. The internal bond value of the panels with expandable microspheres was steadily raised while the surface thickness was increased. The internal bond for the expandable polystyrene with increasing face thickness was reduced. In comparison with conventional particleboards, the specific bending strength and internal bond were increased. In addition, FE-SEM-microscopy and gamma-ray densitometry were used to characterize the panels.

Ultrasonic wave timing inspection was used to detect the internal decay in standing Iranian beech trees (Fagus orientalis). To evaluate the influence of internal decay on ultrasonic velocity, healthy round sections of freshly cut fallen beech trees were selected. Holes [as heart or internal decay indicator and with different shapes (circular and slot) and locations] were manually created and progressively enlarged in the wood section disks, and ultrasonic wave velocity was measured by using a commercial ultrasonic tester (Sylvatest Duo). The results showed that ultrasonic wave velocity linearly and significantly decreased by increasing hole dimensions, and location of holes had no influence on the extent and trend of velocity decrease. Although slots covered a small volume fraction of disks, they had a greater effect on ultrasonic velocities reduction as compared with circular holes.

Geopolymers show good potential to be used as free formaldehyde-based binder to produce wood-based panels. Hence, the objective of this research was to investigate the geopolymer composition as binder on the physical and mechanical properties of multi-layered plywood. The geopolymer binder was prepared based on kaolin and metakaolin as the major aluminosilicate powder that were substituted with different contents of silica fume. The results showed that the substitution of aluminosilicate with silica fume (up to 20% based on weight) in the geopolymer mixture modified the chemistry of the geopolymerisation, and hence, improved the amorphous structures of the geopolymer binder. In summary, the substitution of aluminosilicate with silica fume (up to 20% based on weight) in the geopolymer mixture improved the geopolymer binder cohesion, reduced the binder viscosity, reduced the binder curing time, increased the binder penetration into the superficial wood cells, increased the binder shear strength, increased the bending strength of plywood, and accordingly, reduced the plywood stiffness. Notably, none of the plywood samples did delaminate even after 672 h water immersion, implying that the geopolymer binder-based products have a better stability in water compared to some organic binders (e.g., adhesives based on tannin, soya and starch), which suffer from hydrolysis after immersion in water. All in all, the geopolymer binder based on metakaolin showed promising potential to be used as formaldehyde-free binder to produce plywood.

One-step manufacturing process (in-situ foaming) provide great potential for the production of foam core panels. Polyurethane (PU) foam showed good applicability for use for in-situ foaming. Here, the effect of ingredient ratios of rigid PU foam on foam performance and panel properties is investigated. It was observed that the isocyanate (ISO) content and polyols (PO) type and content significantly change the foam and panel properties. Foam cell density, as the most important factor influencing the foam characteristics, was higher in foams with higher ISO and polyether content. Bending strength, internal bond and screw withdrawal resistance of the foam core panels were significantly enhanced when the ISO and polyether content was increased in the foam formulation. Varying the ISO content had no influence on panel properties with higher content of polyester (60%) in the PO blend. Varying the foam ingredient ratios did not change the thickness swelling, while the water absorption was dependent on the foam components ratios. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44722.

In this research, a sandwich panel with particleboard as surface layers and rigid polyurethane (PU) foam as core layers (foam-core particleboard) was produced with a one-step in situ foaming proces...