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Traditional wood-based composites are bonded with synthetic formaldehyde-based adhesives [[1]]. 10.1155/2019/5256897 29 Antov P., Savov V., Neykov N. Reduction of Formaldehyde Emission from Engineered Wood Panels by Formaldehyde Scavengers - A Review. Another alternative to the use of synthetic formaldehyde-based adhesives is to manufacture binderless wood composites [[48]], since wood is a natural polymer material which is rich in lignocellulosic compounds such as cellulose, hemicellulose, and lignin. The properties of co-extruded wood/polyethylene composites (Co-WPCs) were improved by filling the shell and wood fiber layers with low-cost nano-silica (nSiO SB 2 sb ) and micro-silica (mSiO SB 2 sb ) [[34]]. [Extracted from the article]

Electronics in furniture and construction materials, in particular technologies which allow for a flexible and cable-free connection of electronics in such materials, are gaining broader interest. This study shows a further development of a concept to obtain highly conductive medium-density fibreboard panels (MDF) for furniture application. MDF were produced using two mixing processes (wet and dry) for wood and carbon fibres to investigate the effects of resin type (urea formaldehyde (UF) and polymeric methylene diphenyl diisocyanate (pMDI)) and carbon fibre content on their mechanical, physical, and electrical properties. Overall, wet mixed fibres showed better electrical but reduced mechanical properties. Modulus of elasticity (MOE) and bending strength (MOR) values of 3500 MPa and 35 MPa, respectively, and internal bond (IB) values of 0.45 to 0.65 MPa with electrical conductivities of up to 230 S/m were achieved. The technology has been successfully implemented in a demonstration object showing the application in a small piece of furniture. [ABSTRACT FROM AUTHOR]

The ongoing transition from a linear to a circular, low-carbon bioeconomy is crucial for reducing the consumption of global natural resources, minimizing waste generation, reducing carbon emissions, and creating more sustainable growth and jobs, the prerequisites necessary to achieve climate neutrality targets and stop biodiversity loss. The harmful formaldehyde released from wood composites can be reduced by adding formaldehyde scavengers to conventional adhesive systems, through the surface treatment of finished wood composites, or by using novel biobased wood adhesives as environmentally friendly alternatives to traditional thermosetting resins [[39], [41], [43]]. Another alternative to formaldehyde-based adhesives is the manufacture of binderless wood-based panels, since wood represents a natural polymeric material abundant in lignocellulosic constituents, such as cellulose, hemicelluloses, and lignin [[44], [46], [48], [50], [52]]. [Extracted from the article]

In the context of natural resource scarcity, environmental challenges and human health concerns, the development of alternative solutions becomes crucial to sustainable development. Sustainable and renewable protein-containing materials such as soy or canola have proved to have wood bonding properties comparable to those of synthetic binders. In addition, the availability of canola meal offers a great possibility for the development of bio-adhesives for the wood-based panel industry. Furthermore, direct utilization of canola meal helps to avoid expensive and low-yield protein isolation processes. Using three different solvent solutions (water and 1 mol and 2 mol sodium hydroxide), canola-based bio-adhesives were prepared and used for the production of medium-density fiberboards (with 10 mm thickness and 800 kg/m3 target density) and three-layer particleboards (with 15 mm thickness and 640 kg/m3 target density). The produced boards were tested for their mechanical properties and dimensional stability according to European norms. With the MDFs' bending strength values above 40 N/mm2 and internal bonding strength greater than 0.5 N/mm2, the results show that there is indeed a possibility to achieve good mechanical properties using canola meal as a binder. The use of NaOH solutions as denaturants, as well as the addition of colasol, helped improve the bonding properties of the boards by 35.49% and 64.52% for 1 mol and 2 mol NaOH solutions, respectively. The obtained results show that the developed canola-based bio-adhesive can compete with conventional ones. However, despite the good mechanical properties of the produced boards, their poor dimensional stability due to the low water resistance of natural proteins suggests further improvement for industrial application. [ABSTRACT FROM AUTHOR]

In this research, the special effects of graphene oxide nanoparticle charging (0, 2, 4, 6, wt.%) on the properties of medium-density fiberboard were examined. Physical and mechanical properties of the panels were determined conferring the method of European Norm standards. The consequences exhibited substantial enhancement in mechanical properties, explicitly in modulus of rupture, modulus of elasticity and internal bonding for 2–6% nanoparticle addition in a urea–formaldehyde resin. The mechanical properties, i.e., internal bond, modulus of elasticity and modulus of rupture were improved by 28.5%, 19.22% and 38.8%, respectively. Results also show a clear enhancement in thickness swelling and water absorption. The physical properties of thickness swelling, water absorption and thermal conductivity were improved up to 50%, 19.5% and 39.79%, respectively. The addition of graphene oxide nanoparticles strongly affected the curing time of the urea–formaldehyde resin and improved its thermal stability. [ABSTRACT FROM AUTHOR]

Wood is an increasingly demanded renewable resource and an important raw material for construction and materials. In addition, new consumption habits are leading to the production of ever greater volumes of waste wood, which constitutes a feedstock that can be mobilized for the cascade production of new materials such as particleboard. However, current legislation and wood waste recycling processes need to be improved in order to maximize the volumes that can be reused and to upgrade the properties of the recycled wood. This review describes wood waste flows and volumes available in Europe, the current French and European legislation, and the innovations under development in this field: innovative automated sorting techniques, physical-chemical processes for cleaning residual glue from the surface of wood particles, cleaning of MDF, and bioremediation processes for cleaning hazardous wood contaminated by heavy metals or creosote. [ABSTRACT FROM AUTHOR]

Wood-based products usually have serious limitations concerning contact with water, both because wood is a hygroscopic material and because the commonly used binder has low moisture resistance. This paper studies the effect of panel moisture content (MC) on the physico-mechanical properties of medium density fiberboards (MDF). Several commercial MDF boards produced in Europe were stored at room temperature and relative humidity (RH) for 9 weeks (approx. range 15–20 °C and 50–85% RH). Every week, a strip of each MDF board was cut out, divided into 5 × 5 cm test pieces and its internal bond strength (IB) was measured. A strong influence of MDF moisture content on internal bond strength was observed and therefore IB test pieces were stored in a climatic chamber (either at 20 °C, 55% RH and at 20 °C, 70% RH). A decreasing linear relation was established between IB and MC. It was found that this effect is reversible: after drying, internal bond strength rises again (following a slight hysteresis). This work reinforces the importance of conditioned storage before board properties analysis, as described in European Standard EN 319. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of iron oxide (Fe2O3) nanoparticles on the physical properties of medium density fiberboard (MDF). In this study, three different nano iron oxide loadings, i.e., 0.5, 1.5 and 2.5 wt %, and untreated poplar fibers were used. The iron oxide (Fe2O3) nanoparticles were initially dispersed into urea formaldehyde resin using a high-vacuum mechanical stirrer before being incorporated into natural fibers. The untreated poplar fibers were wound onto metal frames to produce dry mat layers. Twenty different composite samples were made. All composite samples were tested for physical properties, i.e., thickness swelling, water absorption, moisture content and density in accordance with standards EN-317, ASTM D570, EN-322 and EN-323 respectively. Based on the results, it was found that the incorporation of homogeneously dispersed iron oxide nanoparticles significantly improved thickness swelling (Ts). Moreover, water absorption (WA) improved by up to 49.18 and 34.54%, respectively, at the highest loading of 2.5 wt %. Microstructure was investigated and characterized with scanning electron microscopy (SEM), x-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) and we examined whether iron oxide nanoparticles exhibit good interactions with urea formaldehyde and poplar wood fibers. Heat and mass transfer investigation in the form of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) was carried out due to the impact of Fe2O3 nanoparticles. The curing temperature and thermal stability of the resin were enhanced due to the addition of Fe2O3 nanoparticles. A one-way ANOVA statistical analysis was established to effectively control the use of Fe2O3 nanoparticles. Therefore, the presence of iron oxide nanoparticles in an epoxy polymer contributes to a stiffer matrix that, effectively, enhances the capability of improving the physical properties of nano MDF. [ABSTRACT FROM AUTHOR]

In this study, a lignin-based polyacid catalyst was synthesized via two steps to enhance water resistance of urea–formaldehyde (UF) resins. The first steps involved a hydroxymethylation reaction to increase the hydroxyl content in lignin. Then, hydroxymethylated lignins were reacted with maleic anhydride to form maleated lignin-based polyacids. The acid groups were expected to function as acid catalysts to catalyze the curing process of UF resin. In order to elucidate the structural variation, 3-methoxy-4-hydroxyphenylpropane as a typical guaiacol lignin structural unit was used as a model compound to observe the hydroxymethylation and the reaction with maleic anhydride analyzed by 1H and 13C NMR. After the structural analysis of synthesized lignin-based polyacid by FTIR and 13C NMR, it was used to produce UF resin as an adhesive in plywood and medium density fiberboard (MDF) production, respectively. The results showed that when the addition of lignin-based polyacid was 5% in plywood, it could effectively improve the water resistance of UF resins as compared to commercial additive NH4Cl. It also exhibited a lower formaldehyde emission. Like plywood, lignin-based catalysts used in medium density fiberboard production could not only maintain the mechanical properties, but also inhibit the water adsorption of fiberboards. [ABSTRACT FROM AUTHOR]