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Chitosan and bio-based epoxy resins have emerged as promising formaldehyde-free replacements for traditional urea–formaldehyde (UF) adhesives in engineered wood products. This study evaluated five chitosan-to-epoxy weight ratios (3:1, 2:1, 1:1, 1:2, 1:3) as adhesives for hot-pressing medium density fiberboards (MDF) using mixed hardwood fibers. Increasing the epoxy ratio reduced viscosity and gel time, facilitating spraying and fast curing. The density of the formulated MDFs increased with higher epoxy ratios, ranging from 679 kg/m3 for the 3:1 ratio to 701 kg/m3 for the 1:3 formulation, meeting the 500–900 kg/m3 density range specified in EN 323. The 1:3 epoxy-rich formulation enhanced modulus of rupture (MOR) to 31 MPa and modulus of elasticity (MOE) to 2392 MPa, exceeding the minimum requirements of 16 MPa and 1500 MPa set out in EN 310 and EN 316, respectively. Dimensional stability peaked at 5% thickness swelling for the 1:3 formulation after 24 h water soaking, fulfilling the < 25% requirement per EN 316. Internal bond strength reached a maximum of 0.98 MPa for the 3:1 chitosan-rich formulation, satisfying the 0.40 MPa minimum per EN 319. One-way ANOVA tests showed the adhesive ratio had a significant effect on mechanical properties and dimensional stability at 95–99% confidence levels. Duncan's multiple range test revealed the 1:3 ratio boards exhibited statistically significant improvements compared to untreated group. Overall, tailoring the ratios achieved well-balanced properties for MOR, MOE, and dimensional stability, demonstrating potential to replace UF resins. [ABSTRACT FROM AUTHOR]

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]

This study aims to find the possibility of producing eco-friendly thin Medium Density Fibrepanels (MDF) with the participation of corn stalk fibres and using lignosulphonate as a bio-based binder. The main novelty in the research is the establishment of the effect of additional heat treatment on the properties of MDF manufactured with the participation of non-wood lignocellulosic raw materials and bonded with bio-based adhesive -- lignosulphonate. Panels with 15% lignosulphonate content and variation of the content of corn stalk fibres from 0% to 30% were manufactured. Previous experiments showed that when only lignosulfonate is used as a binder, the manufactured panels generally have low waterproofness. To reduce the effect of this main disadvantage, the panels were subjected additionally to heat treatment. The properties of the MDF with and without additional heat treatment were compared. The effect of both the content of corn stalk fibres and the additional heat treatment was found. As a whole, the additional heat treatment improves the properties of MDF produced with lignosulphonate. Still, in case of increased content of corn stalk fibres, it is necessary to apply softened regimes than the ones selected for this study. [ABSTRACT FROM AUTHOR]

Background and Objective: Nowadays, in metropolitan areas, principled and hygienic waste management is very important. Recycling is one of the most appropriate options in waste management. Hereof, the present study was aimed to investigate the possibility of using textile waste fibers in the manufacture of Medium Density Fiberboard (MDF). Materials and Methods: This experimental study was performed on lab-scale. Fabric waste was prepared by separation method at source from a clothing manufacturer in Tehran and converted into fibers. Test boards were made with weight percentage of mixing textile waste fibers to industrial fibers at three levels of 0:100, 10:90 and 15:85, respectively, 10% urea-formaldehyde adhesive, with 16 mm thickness and 0.7 g/cm³ density by hot press. Then, properties of the boards were measured including bending strength, modulus of elasticity, internal bond, hardness, water absorption and thickness swelling. The results were analyzed with ANOVA test. Results: The results of ANOVA showed that the effect of textile waste fibers on the bending strength, modulus of elasticity and swelling thickness of 2 and 24 hours of boards made at 5% probability level was significant. Additionally, the highest values of physical and mechanical properties are related to made boards with 10% of textile waste fibers. Conclusion: The results showed that it is possible to make MDF with textile waste fibers. The use of wastes such as fabrics in the production of new functional products can be considered as one of the strategies to reduce waste and thus to maintain human health and the environment. [ABSTRACT FROM AUTHOR]

Traditional wood-based panels composed of wood and petroleum based adhesives is widely used in furniture manufacturing and construction industries. However, these adhesives are not biodegradable, inhibiting the recycling of artificial board. More seriously, the emission of carcinogenic formaldehyde will lead to severe pollution and environmental issues. This study presents a method for preparing self-bonding composites. Waste poplar powder is used as raw material in the biocomposite, in which exogenous lignin is added, and lignin is extracted from the waste of the paper industry - black liquor, which is beneficial to the environment and the recycling of resources. The resulting biocomposites are characterized by aldehyde-free, better strength, and water stability. The dimensional stability and mechanical strength, bending strength (84.40 MPa), and tensile strength (35.40 MPa) of the biocomposite are 2.0 and 1.6 times that of composites obtained by hot pressing without pretreatment and are 2.7 and 2.4 times that of medium density fiberboard (MDF), lignin plays an important role as an adhesive, which is the key to improving mechanical properties. Moreover, the biocomposite features higher water stability and fire resistance than the traditional wood fiberboard. In conclusion, the developed black liquor-wood biocomposites are potential alternatives used to replace the formaldehyde wood-based fiberboard. [Display omitted] • An aldehyde-free wood-based panel was prepared by a resource-saving method. • The flexural and tensile strengths are 84.40 MPa and 35.40 MPa. [ABSTRACT FROM AUTHOR]

Owing to the similarities in raw materials, technology, and application fields between fiberboard and particleboard, it is crucial to perform a comparative life cycle assessment (LCA) on these two types of panels. This comparison can greatly contribute to a comprehensive understanding of the environmental impact of these panels. However, there is a limited number of studies available regarding the comparative LCA study of these panels. Therefore, in this study, the environmental effects of manufacturing process of dry-process fiberboard (medium-density fiberboard, MDF) and particleboard (PB) were compared. A cradle-to-gate LCA model was developed using eFootprint software. The results showed that PB exhibited better environmental performance than MDF because of the lower power consumption and the amount of urea-formaldehyde (UF) resin required in the manufacturing process. The total environmental impact of PB from cradle to gate was 27.5% lower than that of MDF, and the eco-efficiency of PB was 18.8% higher than that of MDF. Regardless of the panel type, the greatest environmental effect occurred in the raw and auxiliary materials production phase, followed by the board production phase. The environmental effect of the transportation phase was minimal. The production of UF resin and the consumption of electricity were identified as the main environmental hotspots. Finally, two approaches to enhance environmental performance were proposed and applied: first, replacing UF resin with a soy-based adhesive, and second, switching from thermal power to hydropower. In addition, the environmental impacts before and after implementing these approaches were compared. [Display omitted] • Particleboard has better environmental performance than medium density fiberboard. • Urea-formaldehyde resin and electricity are the key environmental hotspots. • Soy-based adhesive doesn't outperform urea-formaldehyde resin in all impacts. [ABSTRACT FROM AUTHOR]

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 formaldehyde emission class of wood level was achieved. It is supposed that the emission of formaldehyde might well increase again while the reactive sites of the chitosan added were already saturated with formaldehyde. Hence, performing of long-term formaldehyde emission is recommended for further analysis based on the obtained results in this study. [ABSTRACT FROM AUTHOR]

An increase in demand on solid wood that is insufficient supply to meet in the world necessarily directed to other engineering materials that could be an alternative to the solid wood. In this context, instead of using solid wood in furniture and construction industry, wood-based panels such as medium density fiberboard (MDF) and particleboard (PB) have become widely used as construction material. Limited research has been done in the field of fastener performance as mechanical properties with different parameters in the joints constructed with these panels. Therefore, in this study, the parameters of screw type, pilot hole, screw orientation, water treatment and adhesives were investigated in MDF and PB. The results indicated that the highest direct screw withdrawal (DSW) resistance was observed in the test blocks applied with PU and the lowest DSW resistance was in the test blocks without a pilot hole drilled in both materials. In addition, MDF in general had better DSW resistance than PB in almost all combinations of the parameters. The treatment of water into MDF and PB test blocks negatively affects the DSW resistance. The DSW resistance in the face orientation was found to be higher than the corresponding ones in the side orientation in both materials. [ABSTRACT FROM AUTHOR]

Oxidized starch (OS) adhesives with a balance between their adhesion and disintegration properties were prepared by controlling the degree of oxidation and modifying the cross-linker type and level to replace ureaformaldehyde (UF) resins for easy recycling of medium density fiberboard (MDF). Four molar ratios of H2O2/starch, two types of cross-linker, i.e., blocked-pMDI (B-pMDI) and citric acid (CA), and three levels of the crosslinkers were employed to tailor the performance of the OS adhesives. The OS reacted with the isocyanate groups from the B-pMDI to form amide linkages, while it formed ester linkages by reacting with the CA. The resulting B-pMDI/OS-bonded MDF had better physical and mechanical properties than the CA/OS-bonded MDF, with comparable adhesion (0.34 MPa) to UF resins and ten times greater degree of fiber disintegration than UF resins. The combination of a 0.5 molar ratio OS with 7.5 wt% of BpMDI produced MDF exhibiting an optimal balance between adhesion and disintegration, suggesting that such OS adhesives could someday replace UF resins in manufacturing and recycling of MDF without formaldehyde emission. [ABSTRACT FROM AUTHOR]

As a way of reducing the formaldehyde emission and improving the properties of medium density fiberboard (MDF), this study investigated the effects of nanoclay and modified nanoclay with 3-aminopropyltriethoxysilane (APTES) and l -Lysine (Lys) on the MDF. The XRD, FTIR, and CHN anaLyses showed that nanoclay was successfully modified with APTES and Lys. 1.5, 2, and 2.5% of nanoclay and modified nanoclay were added into UF resin (based on the dry weight), and the mixtures were used to produce MDF. Changes in formaldehyde emissions were determined by the desiccator method. In addition, the modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding (IB), thickness swelling (TS), and water absorption (WA) of the boards were measured. The results showed that adding nanoclay (5–25%) and modified nanoclay with APTES (42–61%) and Lys (38–50%) reduced formaldehyde emission. Meanwhile, the mechanical and physical properties of the boards also improved by adding nanoclay and modified nanoclay. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Synthesis of UF resins in the wood-based composites. • Effects of catalysts (NH 4) 2 SO 4 , NH 4 Cl, H 2 SO 4 and HCl during UF resins synthesis. • Investigated by 13C NMR and DSC. • (NH 4) 2 SO 4 catalyzed UF adhesive with the best overall mechanical properties. • The HCl catalyst was considered to be chemically least active. Abstract Recently, there has been a rapid growth in research and innovation in the synthesis of UF resins in the wood-based composites area. Much effort has gone into increasing their mechanical performance to extend the capabilities and application of this group of materials. This paper, for the first time, defines the research on the use of ammonium salts not as hardeners but in the synthesis of UF resins. The objective of this study was to investigated the effects of various types of catalysts (ammonium sulfate, ammonium chloride, sulfuric acid and hydrochloric acid) during UF resins synthesis on formaldehyde emission and characteristics of urea–formaldehyde (UF) adhesives for the manufacture of medium density fiberboard. These were investigated by 13C Nuclear Magnetic Resonance (13C NMR) and differential scanning calorimetry (DSC), and as a result some of the physical and mechanical properties of medium density fiberboard (MDF) panels bonded with different UF resins were evaluated. The resins structure examined by 13C NMR spectroscopy showed that a resin catalyzed by (NH 4) 2 SO 4 had a higher proportion of hydroxymethyl groups (mostly HN C H 2 OH) resulting in a higher level of formaldehyde emission. A resin catalyzed by NH 4 Cl gave the highest proportion of methylene groups. A resin catalyzed by H 2 SO 4 yielded the highest proportion of methylene groups in di- or tri-substituted ureas but the lowest proportion of mono-substituted urea. It was of interest that (NH 4) 2 SO 4 catalyzed UF adhesive yielded the best overall mechanical properties for the medium density fiber board (MDF) bonded with it. Conversely, it also presented the shortest shelf life and gelled in about 15 days, which could be related to its high reactivity and shortest gel time. Medium Density Fiberboard (MDF) panels bonded with UF adhesives without any ammonium salt (thus with either H 2 SO 4 or HCl) had lower IB strength, MOR and MOE. The HCl catalyst was considered to be chemically least active, yielding the lowest cohesive energy, and resulted in panels presenting a poor performance as shown by their lowest IB (internal bond) strength, modulus of elasticity (MOE), and modulus of rupture (MOR) and highest thickness swelling, with the exception of the free formaldehyde content. [ABSTRACT FROM AUTHOR]

Particleboard (PB), medium density fibreboard (MDF), oriented strand board (OSB) and plywood (PW), the most common products of wood panel industry, are produced by means of synthetic adhesives (resins). From the wide range of adhesives employed, amino resins as combination of formaldehyde (F) and urea (U), and melamine (M) are the most important ones, which include the most popular UF and MUF resins. This review is an introduction to the UF and MUF synthesis processes, and also addresses the key parameters for the performance of these adhesives and gives an overview about the final characteristics of PB and MDF prepared with amino resins. The characterization methods for amino resins and panels are outlined. The strategies for the optimization of resin properties and pressing conditions are discussed in terms of their good performance also under conditions of low formaldehyde emission. [ABSTRACT FROM AUTHOR]

Distillers dried grains with solubles (DDGS) were employed as a biobased resin/adhesive. DDGS were defatted with hexane, ball ground, and screened prior to use. DDGS flour was mixed dry with Paulownia wood (PW) to make composites using the following conditions: temperature of 150 to 195 °C, PW particle sizes of ≤ 75 to 1700 µm, pressure of 2.1 to 5.6 MPa, and using DDGS dosages of 10 to 100%. Molded composites were evaluated for their flexural properties. Composites were examined with Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and X-ray diffraction. The best flexural properties were obtained from composites containing 50% DDGS and 50% PW, using 180 to 250 µm PW particles, pressed at 5.6 MPa, and employing 185 °C. Flexural properties of DDGS-PW composites were similar to composites fabricated using soybean flour (Prolia) as the resin/adhesive. Dimensional stability properties (water absorbance and thickness swelling) of DDGS-PW and Prolia-PW composites were similar. DDGSPW composite properties satisfied several European Committee Industry Standards for fiberboards in terms of flexural properties but were inferior in terms of thickness swelling properties. [ABSTRACT FROM AUTHOR]

A highly efficient method was developed for preparing chitosan-lignin wood adhesives with high performance using chitosan and ammonium lignosulfonate as main raw material and performance of the resulting adhesives was evaluated by manufacturing medium density fiberboard (MDF). The effects of chitosan-lignin adhesive content and lignin/chitosan weight ratio on the physical and mechanical properties of MDF and the optimal method to prepare and utilize chitosan-lignin wood adhesives were investigated. The results indicated that chitosan had important effects on bonding strength and water resistance and the performance of chitosan-lignin adhesive improved significantly with the optimal method: chitosan-lignin adhesive content of 6% and lignin/chitosan weight ratio of 1:2. The fractures in the bonded joints and the chitosan-lignin adhesive were analyzed via scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The SEM image analysis verified the high performance of the chitosan-lignin adhesive. The FTIR analysis indicated that interactions due to hydrogen bonding between chitosan and lignin occurred. The results of thermal stability analysis validated this and showed that the thermal stability of the interactions was not high. [ABSTRACT FROM AUTHOR]

Laccase, an enzyme capable of degrading lignin, has become an effective agent for green processing and has great significance for the protection of the environment and the development of a low-carbon economy. In this work, wood fibers were selected as the raw material, and with activation by a laccase-mediator system, lignin was changed to a natural adhesive material, and the high temperature/high pressure method was used to prepare medium density fiberboard (MDF). The bonding mechanism was explored with measurements of Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), environmental scanning electron microscope (ESEM), and X-ray diffraction (XRD). It was found that the self-adhesive effect was realized through esterification, hydrogen bonding, polycondensation, coupling, and a Schiff base reaction, among which coupling and polycondensation were the primary reactions. The chemical bonds between the MDF interior and surface varied because of the mobility of the lignin during the reaction. [ABSTRACT FROM AUTHOR]

This study investigated the pull off strengths of various laminated medium density fiberboards (MDFs). The surface roughness of the MDF, adhesive type, and veneer type were all studied. Polyvinylacetate (PVAc), urea formaldehyde (UF), and gluten were used as the adhesives for beech, pine, and oak veneers. There were a total of 216 experimental specimens that were tested according to the principles specified in the TS 5339 (1987) standard. According to the statistical analyses of the data obtained from the tests, surface roughness, veneer species, and adhesive type all affected the pull-off strength of the laminated MDF. The highest pull-off strength (2.88 N/mm2) was obtained with the MDF unsanded with 120-grit abrasive and laminated with PVAc adhesive and pine veneer. The lowest pull-off strength (1.60 N/mm²) was obtained with the unsanded MDF laminated with PVAc adhesive and oak veneer. [ABSTRACT FROM AUTHOR]

In this study, for a better understanding of the hot-pressing process, the influence of adhesive content (AC) on various features of a typical pressing schedule for medium-density fiberboard (MDF) production, including fiber mat compressibility, heat transfer during hot-pressing, density profile and board properties, were evaluated. It was found that increasing the AC (urea formaldehyde) leads to faster heat transfer towards the mat's central plane, mainly due to higher heat release from the adhesive polycondensation reaction. Moreover, the results indicate that the time needed to reach the critical mark of 100 °C in the central plane of the mat depends on the duration of the first densification level (FD). Importantly, the pressure peaks (pmax and p2nd) needed for mat densification are significantly reduced when increasing the AC, which might be attributed to the slippery effect created by the adhesive on the fiber surfaces. The duration of the FD also showed obvious effects on the intermediate density maxima (ρinter) and the core layer density (ρcore). In general, the physical and mechanical properties of MDF panels are significantly impacted by the pressing schedule and AC. All in all, the results of this study are valuable information for refining existing rheological models to improve their accuracy and their ability to simulate the vertical density profile during industrial production. [ABSTRACT FROM AUTHOR]

Abstract: In the present work a small percentage of activated charcoal was added in the thermosetting urea–formaldehyde (UF) resin and the performance of adhesives and wood composite was observed. The effect of activated charcoal on the curing kinetics and the Crosslink density of UF resin was investigated, using differential scanning calorimetry. The activated charcoal has an accelerating effect on the curing of the UF resin. The Crosslink density of resin increases and the activation energy decreases. The influence of the activated charcoal addition was particularly noted in medium density fiberboard by the increase in the value of modulus of rupture and internal bond strength of the panel, a direct indication of the performance improvement with the addition of a small amount of activated charcoal. The formaldehyde emission significantly decreases with the addition of activated charcoal. [Copyright &y& Elsevier]

Confocal microscopy has been used to investigate the behavior of urea-melamine-formaldehyde (UMF) resin after being sprayed onto wood fibers. Samples of wood fibers were dyed with Toluidine Blue O (TBO) to create a contrast between the resin and the fiber when studied under a confocal laser scanning microscope (CLSM). The resin droplet penetration into the fiber cell wall was evaluated from the three-dimensional images generated by the CLSM. Experimental conditions were varied to determine their influence on the penetration of the resin into the cell wall. The Washburn equation was used to model the penetration process. The model takes into account variations of the resin viscosity with temperature and time. The penetration rate was found to be related to resin viscosity. The penetration depth can be as low as 1 μm if the resin is applied on a dry spruce fiber in a drum mixer. The maximum penetration depth corresponds to the thickness of the cell wall, which can vary from 10 to 20 μm for spruce. Further work should lead to the development of a more effective resin that could be used to make boards with the same performance but less resin. [ABSTRACT FROM AUTHOR]

In this research cellulose nanofibers (CNF) were successfully extracted from rice straw through a chemomechanical method and then mixed with urea-formaldehyde (UF) adhesive for the production of medium density fiberboard (MDF). The industrial grade liquid urea-formaldehyde (UF) resin with formaldehyde: urea molar ratio of 1.15 was modified by adding 0.5, 1.5 and 2 wt % of nanofibrillated cellulose (CNF) based on UF resin solids. The morphology, gel time, viscosity, and the non-volatile solid content of the modified UF adhesive were investigated. Formaldehyde emission and some mechanical properties modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond strength (IB)) of the resulting MDF panels were measured. Solids content and viscosity of the UF adhesive decreased while gel time increased by mixing CNF with the resin. The formaldehyde emission of the panels made with UF containing CNF was lower than that of the panels made from neat UF while MOR, MOE and IB values increased by increasing the CNF content in the panels. [ABSTRACT FROM AUTHOR]