Properties Of Plywood Research Articles

Enhancing the Performance of Layered Wood Composites Through the Non-Food Application of Dietary Fiber in Their Bonding Matrix

Rye flour is a commonly used filler in plywood production, made from finely ground rye grains. It enhances glue viscosity, ensuring even distribution and better adhesion, which improves the plywood’s mechanical properties, dimensional stability, and resistance to warping. Additionally, rye flour increases the plywood’s strength and durability, making it more resistant to mechanical damage and external factors. Its affordability and availability further support its widespread use in plywood production. However, the growing availability of new raw materials has sparked interest in alternative fillers, especially considering food waste challenges caused by low demand or poor household management. This study explores the potential of spirulina, bamboo flour, lupine flour, and coconut flour as alternative fillers to rye flour, being part of the food chain, in three-layer plywood production. Plywood panels were manufactured using birch and pine veneers, urea-formaldehyde resin, and varying filler contents (10, 15, and 20 parts by weight/pbw). Key mechanical properties were evaluated, including modulus of elasticity (MOE), modulus of rupture (MOR), shear strength, density profile, and filler water absorption. The highest MOE for hardwood plywood was observed with coconut flour (20 pbw, 17,228 N mm−2). Conversely, the lowest MOE values were recorded for coniferous plywood with spirulina (8440 N mm−2). For MOR, the best performance in softwood was achieved using lupine flour (10 pbw, 113 N mm−2), while coconut flour yielded the highest MOR in hardwood plywood (20 pbw, 177 N mm−2). Spirulina exhibited the lowest MOR (72 N mm−2, 15 pbw). Shear strength peaked with lupine and coconut flour. The filler composition determines adhesive properties and bond performance through water absorption, structural interactions, and filler content optimization. These findings emphasize the potential for fine-tuning alternative fillers to achieve desired mechanical performance, ensuring sustainable and efficient plywood production. These also demonstrate the potential of certain alternative fillers, particularly coconut and lupine flours, excluded from the food value chain, in improving specific properties of plywood.

Enhanced formaldehyde oxidation of plywood using MnO2 nanoflowers supported on porous hydrothermal carbon at ambient temperature

MnO2 nanoflowers were supported on porous hydrothermal carbon via in situ loading and used for the catalytic oxidation of formaldehyde from plywood manufactured with UF adhesive. The prepared MnO2 had a δ-type structure. The use of hydrothermal carbon (Hcs) improved the dispersion of active components in the materials and provided space for the catalytic reactions. Hcs/MnO2 exhibited catalytic activity and stability during formaldehyde oxidation at room temperature. The formaldehyde removal efficiency reached 90.43 % in 30 min. The Hcs/MnO2 had more oxygen vacancies than the MnO2 catalyst, providing more abundant active substances such as -OH, O2-, O- and other active substances to promote the catalytic reaction. The effects of Hcs/MnO2 on the formaldehyde emission and the mechanical properties of plywood were investigated. The MOR, MOE and bonding strength of the Hcs/MnO2-loaded plywood with 9 % Hcs were 51.1 MPa, 2994 MPa, and 0.8 MPa, respectively. After 28 d of exposure, the formaldehyde emitted from the plywood treated with Hcs/MnO2 decreased to 0.023 mg/m3, which fulfilled the requirement for ENF grading. The controlled release of free formaldehyde from plywood by Hcs/MnO2 was reflected by changes in mass transfer and catalytic oxidation. The manganese oxides in the micropores of the wood reduced the diffusion coefficient of free formaldehyde and hindered migration through the substrate. Once the concentration of formaldehyde decreased to a certain level, it was degraded by Hcs/MnO2, thus removing formaldehyde from the source.

An organic-inorganic dual network built in fast-growing wood veneers to improve the flame retardant and mechanical properties of plywood

Fast-growing wood is widely used in plywood production due to its short growth cycle and low cost. However, its loose fiber structure, inferior material quality, and high flammability significantly limit the application range of plywood products and hinder high-value utilization. This paper reports a simple method for modifying fast-growing wood veneers. We modified phenolic resin with Mg(OH)₂@nano-silica composite particles and impregnated it into the veneers, constructing an organic-inorganic hybrid dual-network structure on both the surface and interior of the veneers. The plywood prepared from the modified veneers exhibited a bending strength of 115.6 MPa, a modulus of elasticity of 9.7 GPa, and a wet shear strength of 2.1 MPa, representing increases of 86.1 %, 47.0 %, and 90.9 %, respectively, compared to plywood made from unmodified veneers. Additionally, the peak heat release rate decreased by 15.3 %, and the ignition time was extended to 26 s. The uniformly distributed inorganic network effectively mitigated stress concentration and, together with the phenolic resin, formed an efficient thermal insulation layer, enhancing the flame retardancy of the material. This study offers a simple and effective treatment method for reinforcing fast-growing wood veneers, promoting the use of fast-growing wood in high-performance applications.

Performance Evaluation of Carbon Fiber Fabric-Reinforced Formaldehyde-Free High-Strength Plywood.

Plywood is lightweight, strong, and durable, making it a widely used material in building decoration and furniture areas. In this study, formaldehyde-free, high-strength plywood was prepared through the incorporation of carbon fiber fabrics (CFFs) as reinforcement layers and their bonding with maleic anhydride polyethylene (MAPE) films. Various tests were performed to assess the impact of the carbon fiber fabric positioning on the physical and mechanical properties of plywood, including tensile shear strength, flexural strength, water absorption, thickness swelling, and electro-thermal properties. The results revealed that the plywood with CFFs exhibited significantly higher mechanical properties than plywood without CFFs. Particularly, the addition of CFFs increased the tensile strength of the plywood by nearly 54.43%, regardless of the CFFs' position. The symmetric placement of CFFs near the bottom and upper layers of the plywood resulted in a maximum modulus of rupture of 85.6 MPa. These findings were validated by numerical simulations. Scanning electron microscopy analysis of the plywood microstructures revealed that MAPE penetrated both the vessels and xylem of the wood veneers and the pores of the CFFs, thereby improving the mechanical properties of the plywood. Plywood reinforced with CFFs exhibited increased water absorption and thickness swelling after immersion. Additionally, the placement of CFFs influenced the electro-thermal properties of the plywood. Plywood with CFFs positioned near the bottom and upper surfaces exhibited superior thermal conductivity. Overall, this study presents a feasible method for developing high-performance, formaldehyde-free plywood and sustainable wood-based structural materials with potential applications in geothermal flooring.

Introduction of aldehyde groups into surface of pine bark via Cannizzaro reaction to improve Urea-formaldehyde resin properties

Pine bark, a natural and renewable forest residue, was modified using a simple interfacial solid-phase chemical method to design a highly chemically reactive additive for urea-formaldehyde (UF) resin. The modification introduced carbonyl groups onto the bark surface during the glyoxal reaction at the bark-solid interface. Thermal properties, including curing temperatures, of UF, UFB, and UFGB were evaluated using DSC and DMA. Glyoxal modification of bark significantly influenced these properties, facilitating the crosslinking and curing of adhesives. Notably, plywood bonded with UFGB resin released approximately half as much formaldehyde (52.89 % less) compared to plywood bonded with UF resin, reducing from 1.38 to 0.65 mg/L. Additionally, the wet shear strength of plywood increased by 197.3 %, from 0.37 MPa to 1.10 MPa, exceeding the minimum requirement (0.7 MPa) defined by the China national standard (GB/T 17657–2013). The study presents a compelling case for the utilization of glyoxal-modified pine bark as a filler in UF adhesive for plywood manufacturing. The demonstrated improvements in plywood properties and formaldehyde emissions, along with the environmentally friendly nature of the approach, make it a promising avenue for sustainable plywood production. Further investigations into the underlying mechanisms and long-term performance are encouraged to solidify the potential of this technology.

Employing a mixture of fine-particle PKS, glycerol, and citric acid as an eco-friendly binder for plywood production from rubberwood (Hevea brasiliensis) veneer

Biomass-based adhesives, which are environmentally friendly and sustainable materials enabling low formaldehyde wood composites, have garnered interest. Therefore, palm kernel shells (PKS), available as industrial agricultural residue and rich in lignin, are mixed in form of fine particles with glycerol and citric acid, and tested as a candidate for binder in plywood production. The study focused on examining the effects of two factors: the quantity of adhesive used and the pressing temperature. Glycerol and citric acid are low-cost non-toxic chemicals that activate the functional groups and induce changes in the PKS component during hot pressing. Consequently, the mixtures with PKS as fine particles could cross-link with rubberwood veneer, forming a plywood panel with shear strength and bending strength that meet the requirements outlined in ISO 12466-2: part 2, and in Thai industrial standard (TIS 178-2549) for indoor use. The properties of plywood were primarily influenced by the pressing temperature rather than by the quantity of adhesive. Specifically, the temperatures 180 °C and 200 °C enhanced the extent to which the molten binder penetrated the rubberwood surface, consequently improving the mechanical properties and water resistance of the bonding.

Modified Buckwheat Husk as a Filler for Urea-Formaldehyde Resin in Plywood Production.

The aim of the presented research was to determine the suitability of both non-modified and modified buckwheat husk (BH) as a filler for urea-formaldehyde adhesive in plywood production. The effect of two modification methods, acetylation and silanization, was investigated. Infrared spectroscopy outcomes confirmed that both acetylation and silanization of the filler had occurred. Based on the results, it was found that the introduction of BH had a significant effect on both the adhesive properties and the characteristics of the manufactured plywood. The application of non-modified husks led to a reduction in viscosity and an extension of the gelation time, and the produced plywood boards were characterized by reduced bonding quality and increased delamination. Modification of the husk surface by acetylation and silanization with 3-aminopropyltriethoxysilane contributed to the noticeable improvement in the resin properties. On the other hand, the improvement in plywood properties, consisting of the increase in bonding quality and reduced delamination, was observed only in the case of the silanized husk. Furthermore, the use of non-modified and acetylated husk did not significantly influence the formaldehyde emission. The reduction in the investigated emission of formaldehyde was observed only in the case of variants containing 15 and 20% of silanized buckwheat husk.

Research of the Properties of Plywood Based on Urea-Formaldehyde Binder with the Added Multi-Wall Carbon Nanotubes

Research of the Properties of Plywood Based on Urea-Formaldehyde Binder with the Added Multi-Wall Carbon Nanotubes

Study of Mechanical Properties of Plywood and Its Application in Furniture

Study of Mechanical Properties of Plywood and Its Application in Furniture

The effect of pressing parameters and hardener content on the properties of plywood bonded with propylamine-UF adhesive

ABSTRACT Research on reducing the formaldehyde emission from wood-based materials bonded with urea-formaldehyde (UF) resin has attracted the attention of scientists for years. Many studies investigated the possibility of using amines for this purpose; however, the outcomes of the vast majority of them have shown that the limiting factor is reduced resin reactivity and consequently, deterioration of the strength of the resultant materials as well. Therefore, the aim of this research work was to investigate and evaluate the effect of the pressing protocol applied (pressing temperature and time), and hardener content (20% ammonium nitrate solution) on the properties of plywood bonded with UF adhesive system modified with 1% of propylamine. Manufactured plywood was tested in terms of shear strength (in dry and wet conditions) and formaldehyde emission (measured initially and after 4 weeks). Based on the results, it was found that it is possible to produce plywood with equally good characteristics as the reference, non-modified variant by increasing hardener content from 3% to 7%, increasing pressing temperature from 120°C to 150°C, and extending the pressing time from 240 to 300 s. Markedly, the implementation of these adjustments also contributed to a further decrease in formaldehyde emission.

Analyzing the impact of veneer layup direction and heat treatment on plywood strain distribution during bending load by digital image correlation (DIC) technique

In this study, radiata pine veneers and phenol-formaldehyde resin were used to prepare specimens of 5-ply plywood with different layup directions and heat treatments of veneers. The physical and flexural properties of the plywood specimens were assessed, and digital image correlation (DIC) analysis was employed to determine the strain distribution of the plywood under bending loads. The results of the static mechanical strength and DIC tests showed that the plywood with a small-angle veneer layup ([0]5 and [0,22.5,0,22.5,0]) exhibited a better longitudinal modulus of rupture (MOR//), while [0,45,0,45,0] plywood showed the least bending strength and most strain. Moreover, the results revealed that for plywood composed of veneers that were fully heat treated at 200 °C (5T200), the moisture content was efficiently decreased, and the modulus of elasticity parallel to grain (MOE//) was the highest. The DIC images indicated that the largest strain along the x-direction (εxx) was concentrated on the tensile side of untreated plywood (5N) and on the opposite side of plywood composed of heat-treated veneers, except for the plywood composed of veneers treated at 220 °C (5T220). Of these, 5T200 plywood showed the least strain. In addition, the plywood with 200 °C heat-treated veneers instead of face and core layers (NTNTN200) or crossband layers of untreated veneers (TNTNT200) had larger strain values than 5N and 5T200 plywood specimens, with NTNTN200 plywood having the greatest strain. According to the above results, appropriate layering and heat treatment of veneers can effectively improve the dimensional stability and flexural properties of plywood.

Effects of different pressures and veneer moisture content in adjacent layers on properties of PUF bonded plywood

In practice, for the manufacture of plywood, the veneer is usually dried to a moisture level suitable for bonding. However, anatomical differences within and between veneer sheets are a significant factor and some of them may contribute to significant differences in moisture content (MC). The novelty of this work was to study the possibility of using wood veneers of different MC in adjacent layers in one structure of plywood panels and how this affects the physical and mechanical properties of the panels. The Norway spruce (Picea abies L. Karst) wood veneers with mean MC approximately of 2%, 5% and 7% and phenol-urea-formaldehyde (PUF) resin were used in the experiments. The five-layers plywood panels were manufactured at the two pressing pressures of 0.8 MPa and 1.2 MPa. There was no significant difference in the bending and bonding properties, but only wood failure as measured on bonding specimens which showed higher average values on specimens manufactured with high pressure during hot pressing. Higher differences in MC of each veneer with constant MC of the veneer stack didn’t worse bending and bonding properties of plywood.

Isolation and characterization of soda lignin from OPEFB and evaluation of its performance as wood adhesive

The purpose of this study was to explore the mechanical properties of plywood panels that had been bound with lignin-phenol–formaldehyde (LPF) adhesive. LPF, composed of lignin that was extracted from Oil Palm Empty Fruit Bunch (OPEFB) fiber by soda pulping method and characterized by Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (HNMR), and Thermal Gravimetric Analyzer (TGA) analysis. Then, various compositions of soda lignin (10–50 wt%) were used as a phenol substitute in LPF synthesis. The characteristics of the synthesizedadhesive were compared to the properties of phenol formaldehyde (PF) adhesive. Plywood was fabricated with LPF and its mechanical properties were studied and evaluated using industrial standards. The result indicates that the increase of phenol substitution with soda lignin, up to 40%, improves the mechanical properties of plywood. This research demonstrated the use of lignin as a renewable replacement of phenol in PF adhesive formulation.

Properties of Plywood Made of Thermally Treated Veneers Bonded with Castor Oil-Based Polyurethane Adhesive

Wood industries use thermal and thermomechanical treatments as ecological approaches to increase the durability of wood products, avoiding the need for chemical additives. In this regard, the aim of this study was to compare the physical and mechanical properties of plywood made from veneers treated at different temperatures using thermal and thermomechanical processes, with untreated panels serving as a control. The treatment process involved Pinus taeda veneers submitted to treatment in a hot press at 1.0 MPa in a laboratory oven at temperatures of 160 °C, 180 °C, and 200 °C for 30 min. For bonding the veneers, a vegetable-based polyurethane resin derived from castor oil with a grammage of 395 g/m2 was used, applying pressing conditions at 90 °C, 0.6 MPa, and 10 min. Our results indicate that temperature significantly influences plywood properties, playing a key role in the choice of equipment for the treatment process. Regardless of the method employed, the treatment resulted in an improvement in the hydrophobicity of the veneers due to the decrease in hemicellulose content. Notably, the reduction in strength and stiffness caused by the loss of cell wall polymers was not statistically significant. The treatment was successful in softening the wood material, reducing roughness, and increasing wettability. Despite a minimum of 20% reduction in glue line tension, the samples still surpassed the 1 MPa mark, showing satisfactory results. This demonstrates the feasibility of adjusting treatment variables to ensure the proper use of this adhesive.

MECHANICAL PROPERTIES OF PF AND MUF BONDED JUVENILE HYBRID EUCALYPTUS PLYWOODS PRODUCED IN GHANA

To obtain the mechanical properties of plywood produced from six yearold hybrid Eucalyptus in Ghana was the objective of this research. The samples for the experiment were prepared and tested according to GS EN 326-1, GS EN 310, GS EN 314-1, and GS EN 314 -2. The data obtained were analysed using the factorial ANOVA analysis. The mean results obtained for the various treatments were MOE (6520 – 7638 N/mm2), MOR (53.29 – 60.56 N/mm2, shear strength (2.47 – 5.51 N/mm2), failure (72 -90%) and density (725 – 748 kg/m3). The orientation of the surface veneer caused variations among treatments whiles the adhesives PF and MUF largely did not cause any variations among treatments. This study has proven that it is possible to produce sufficiently strong and resistant plywood from the juvenile wood of eucalyptus.

Development of plywood bonded with a novel adhesive film made from polystyrene foam waste dissolved in D-limonene

ABSTRACT The polystyrene film as a formaldehyde-free adhesive for plywood production was developed from polystyrene foam waste (PSF) and D-limonene, extracted from orange peel waste. The influence of the weight ratio of solvent (D-limonene) to foam in the range of 1, 1.5 and 2 (w/w) on the properties of adhesive film and plywood panels was studied. In addition, the effects of pressing temperatures of 150°C, 165°C and 180°C on the properties of the plywood were investigated. The adhesive film was characterized by measuring the melt flow index, the average molecular weight of the polymers and by FTIR. The bonding quality of the adhesive films was investigated by shear strength tests. Integrated gel permeation chromatography has also shown that the average molecular weight of PSF is drastically reduced by doubling the solvent content. Shear strength and bending properties were also significantly reduced by doubling the weight ratio of solvent to foam. The mechanical properties of plywood are positively affected with increasing press temperature to 165°C. In general, plywood bonded with an adhesive film prepared with a solvent to foam weight ratio of 1 and press temperature of 165°C was fulfilled the requirement according to EN314-2 for interior use.

Effect of ultra-low temperature on some mechanical properties of painted and film-coated plywood

Plywood is used for insulation systems in liquid natural gas cargo ships because of its good thermal properties. However, there are only a few research investigating the mechanical properties of plywood exposed to ultra-low temperatures. This study aims to determine how plywood reacts when exposed to ultra-low temperatures, such as - 196 °C. To achieve this purpose, the present study investigated the bending strength, modulus of elasticity, and tensile-shear strength of painted and film-coated plywood under ultra-low temperatures. The mechanical properties of plywood were discovered to be significantly impacted by the ultra-low temperature as a result of this research. Moreover, not only the bending strength of the painted and film-coated plywood increased with decreasing temperature, but also the modules of elasticity of the painted and film-coated plywood increased. At decreasing temperature, the tensile shear strength of the painted and film-coated oven-dried plywood increased, but the ensile-shear strength of painted and film-coated air-dried plywood decreased. The tensile shear strength of air-dried plywood was determined to be more sensitive to the temperature change. Therefore, attention should be paid to plywood used in liquefied natural gas cargo ships with high humidity.

Properties of Plywood Bonded with Formaldehyde-Free Adhesive Based on Poly(vinyl alcohol)–Tannin–Hexamine at Different Formulations and Cold-Pressing Times

The plywood industry’s sustainability, performance, and production costs depend on wood adhesives and the hot pressing technique. In this investigation, a cold-setting plywood adhesive based on polyvinyl alcohol (P), tannin (T), and hexamine (H) was produced. The physical and mechanical properties of plywood were examined at different formulations such as tannin concentration (10% and 20%), hexamine content (5%, 10%, and 15%), and cold-pressing time (3, 6, 12, and 24 h). This study showed that high tannin and hexamine content also increased the solids content, but decreased the average viscosity of the adhesive. Markedly, the cohesion strength of PTH-based adhesives increased from 5.57 Pa at 1/s to 1411.6 Pa at 400/s shear rate, regardless of the adhesive formulation. The shear modulus subsequently decreased as a function of the shear rate and increased with a higher tannin and hexamine content. This study revealed that the higher tannin and hexamine content and longer cold-pressing times could produce plywood with the tested adhesive that met the Japanese standard strength requirements. A combination of PTH-based adhesive prepared with formula 2 and 24 h cold-pressing resulted in the highest TSS value of 1.42 MPa, MOR values of 88.7 MPa, MOE values of 14,025.6 MPa, and wood failure of 47.2%. This study showed the possibility of fabricating eco-friendly plywood panels bonded with PTH-based adhesive using the cold-pressing process as an alternative to conventional plywood.

Determination of the effect of valonia tannin when used as a filler on the formaldehyde emission and adhesion properties of plywood with artificial neural network analysis

Although artificial neural networks (ANN) have been used frequently in engineering applications, it has been determined that they are not preferred much, especially in determining adhesive properties and usage. Hence, this study aimed to determine the effect of urea formaldehyde (UF) resin mixed with valonia tannin obtained from Turkish oak acorns (Quercus aegilops) as a filler on the formaldehyde emission and bonding strength of plywood panels by using ANN modelling. For this purpose, six different valonia tannin contents and three different adhesive usages were chosen, and they were compared to control panels. The formaldehyde emission and bonding strength experimental data obtained according to relevant standards were analysed by using ANN. The prediction models with the best performance and acceptable deviations were determined using statistical and graphical comparisons between the experimental data and the prediction values obtained from the ANN analysis. Using these prediction models, the formaldehyde emission and bonding strength data were obtained according to the amount of valonia tannin and adhesive usage not used in the experimental study. Experimental results have proved that valonia tannin obtained from Turkish oak acorns is a good formaldehyde scavenger for UF adhesives, but it has been determined that it has a negative effect on the bonding strength of plywood. As a result of the ANN analysis, the lowest formaldehyde emission values were obtained from 12% to 15% valonia tannin and 140 g/m2 - 146 g/m2 adhesive usage. The bonding strength values of all the predicted plywood groups exceeded the limit value of the relevant standard except for the 5% valonia tannin and 140 g/m2 - 158 g/m2 adhesive usage.

Influence of Upcycled Post-Treatment Bark Biomass Addition to the Binder on Produced Plywood Properties

The valorization of tree bark through chemical treatment into valuable products, such as bark acid, leads to the formation of process residues with a high solids content. Since they are of natural origin and are able to be suspended in water and acid, research was carried out on the recycling of suberic acid residues (SAR) as a bi-functional component of binder mixtures in the production of plywood. The 5%–20% (5%–30% for curing time) mass content of SAR has been investigated with urea-formaldehyde (UF) resin of about 66% of dry content. The results show that the curing time of the bonding mixture can be reduced to about 38% and 10%, respectively, for hot and cold curing, of the initial curing time for the lowest SAR content. The decreasing curing time of the tested binder mixtures with the increase in SAR content was caused by the increasing amount of acidic filler, since amine resins as UF require acidification hardening, and the curing dynamics are strongly dependent, among others, on the content of the acid medium (curing agent). In the case of hot curing, a SAR content of about 20% allowed us to achieve the curing time of bonding mass with an industrial hardener. Investigations into the mechanical properties of examined panels showed a significant modulus of elasticity (MOE) increase with filler content increase. Similar conclusions can be drawn when analyzing the results of the modulus of rupture (MOR) investigations; however, these were only significant regarding hot-pressed samples. The shear strength of the plywood samples increased with the SAR rise for both cold- and hot-pressed panels. The in-wood damage of samples with SAR filler, hot-pressed, rose up to about 30% for the highest SAR filler content. For cold-pressed samples, no in-wood damage was found. The positive effect of veneer impregnation limiter by resin was identified for SAR acting as a filler. Moreover, a higher density of SAR-containing bonding lines was reached for hot-pressed panels. Therefore, the results confirmed the ability to use the SAR as an upcycled component of the bonding mixture for plywood production.