Poplar Veneer Research Articles

Effects of the Ball Milling Process on the Particle Size of Graphene Oxide and Its Application in Enhancing the Thermal Conductivity of Wood

To improve the dispersion of graphene oxide particles in wood for better thermal conductivity, this paper proposes the feasibility of obtaining graphene oxide with a smaller particle size using ball milling and its application in melamine resin-modified poplar veneer. The median diameter of multilayer graphene oxide was measured to learn the effects of different ball milling conditions on the particle size of graphene oxide, and the optimum ball milling process was chosen. In addition, the microscopic characterization of graphene oxide under the optimum ball milling process was carried out to investigate the microstructural changes in multilayer graphene after ball milling. Furthermore, the thermal conductivity of the graphene oxide/melamine resin-impregnated mixture modified veneer with the optimum ball milling process was also tested. The results show that, under the optimum ball milling process conditions of SDS wet ball milling with a vibration frequency of 30 Hz for 60 min, the particle size of the multilayer graphene was the smallest, and the median diameter could be reduced to 124 nm. Simultaneously, the thermal conductivity of the melamine resin-modified poplar veneer enhanced by the ball-milled graphene reached 0.405 W·m−1·K−1. In addition, it revealed that the number of graphene oxide layers was reduced to four after ball milling. However, the multilayer graphene was partially oxidized, the lamellar structure was destroyed and the crystallinity was reduced.

Chemical and morphological modification of softwood and hardwood surfaces by an oxygen glow discharge plasma

High-energy radiation preferentially degrades cellulose and enriches lignin content at wood surfaces particularly in hardwoods. Accordingly, we hypothesize that a similar effect will occur at surfaces exposed to plasma. We test this hypothesis by plasma-treating pine and poplar veneers and assessing changes in the lignin and holocellulose-derived sugar-content of veneers; quantifying etching of pellets containing lignin and cellulose, and observing etching of different cell wall layers in pine and Homalium. The majority but not all of our results support our hypothesis. Lignin-rich regions of wood cell walls were easier to see after plasma treatment. We discuss the potential uses of plasma-etching for the study of wood ultrastructure and the creation of wood surfaces with self-bonding properties, and conclude that plasma-etching can be used as an alternative to chemical pretreatments for ultrastructural studies of the distribution of lignin in wood cell walls.

Determination of epoxy resin usability for mass production of reinforced laminated veneer lumber

This study is part of a comprehensive study on the industrial production of reinforced laminated wood composites. The main aim of the study is to determine the production parameters of reinforced laminated wood composite board under an optimal production cycle time under temperature and pressure, using epoxy resin cured at room temperature for 24 h. For this purpose, 1.2 mm thick Samsun Poplar (Populus Deltoides I-77/51) veneer layers, three different pressing cycle times (15, 20, and 25 min), three different temperatures (100°C, 120°C, and 140°C), and three different amounts of adhesive (100, 150, and 200 g/m²) were used also 200 g/m² density twill woven glass–carbon fiber fabric was used as the reinforcement layer. In order to determine the production quality of reinforced laminated wood composite boards, the adhesion strength between the reinforcement layer and the wood veneer layer was determined according to TS EN 3969 314-1. Considering the adhesion strengths in terms of production parameters, the best results were observed at 100°C press temperature, 20 min press cycle time, 200 g/m² adhesive amount, and the use of glass fiber woven fabrics for reinforcement. Under these conditions, the best adhesion strength was found to be 4.17 N/mm². When the samples were examined, it was seen that almost all of the failures occurred as a result of the fracture in the wood layer. This indicates that sufficient adhesion can be achieved between the reinforcement layer and the wood layer.

A Comparative Study of Several Properties of Plywood Bonded with Virgin and Recycled LDPE Films

In this work, to better understand the bonding process of plastic plywood panels, the effects of recycled low-density polyethylene (rLDPE) film of three thicknesses (50, 100, and 150 µm) and veneers of four various wood species (beech, birch, hornbeam, and poplar) on the properties of panels were studied. The obtained properties were also compared with the properties of plywood panels bonded by virgin low-density polyethylene (LDPE) film. The results showed that properties of plywood samples bonded with rLDPE and virgin LDPE films differ insignificantly. Samples bonded with rLDPE film demonstrated satisfactory physical and mechanical properties. It was also established that the best mechanical properties of plywood are provided by beech veneer and the lowest by poplar veneer. However, poplar plywood had the best water absorption and swelling thickness, and the bonding strength at the level of birch and hornbeam plywood. The properties of rLDPE-bonded plywood improved with increasing the thickness of the film. The panels bonded with rLDPE film had a close-to-zero formaldehyde content (0.01–0.10 mg/m2·h) and reached the super E0 emission class that allows for defining the laboratory-manufactured plastic-bonded plywood as an eco-friendly composite.

Thermal, flammability and iso-conversional multiple heating rate kinetic studies of impregnated poplar wood veneers

Thermal, flammability and iso-conversional multiple heating rate kinetic studies of impregnated poplar wood veneers

In Situ Polymerization and Flame Retardant Mechanism of Bio-Based Nitrogen and Phosphorus Macromolecular Flame Retardant in Plywood.

To improve the flame retardant performance of plywood and reduce the reagent loss and moisture absorption of the flame retardant, a bio-based supramolecular flame retardant is prepared by vacuum-pressure impregnation and high-temperature in situ polymerization in plywood. The best value of bonding strength appears at 170°C, and the limiting oxygen index (LOI) of 170BF-B plywood is 42.3%. After hot pressing, the moisture absorption rate of the 170BF-B veneer is only 18.51%, while the loss resistance rate achieves 83.45%. Its residue at 700°C is 91.36% higher than that of poplar veneer. In the combustion process, the peak value of heat release rate (PHRR) and heat release rate (HRR) of 170BF-B plywood are only 10.69% and 37.11% of that of untreated plywood. After combustion, an intumescent flame retardant layer exhibits a graphitization trend. In the flame retardant layer, there are not only functional groups, such as P═O, PO4 3- , POC decomposed by flame retardant but also characteristic functional groups of wood fiber, like C═O, CH, etc. The prepolymer BF-B, which is composed of phytic acid, urea, and dicyandiamide polymerized with chitosan or lignocellulose to form a supramolecular flame retardant connected with POC and PON functional groups, thus improving the flame retardant and anti-loss property by in situ polymerization.

Lateral loading behavior of the poplar LVL light wood shear wall

Poplar laminated veneer lumber (poplar LVL) is made of fast-growing poplar veneer and structural adhesive, which can well meet the developing requirement of the modern wood structures. This paper mainly focuses on the lateral loading behavior of the poplar LVL shear wall. For this purpose, six shear wall specimens with different opening types were fabricated and tested under the action of monotonic and cyclic loading. Performances were analyzed on the failure pattern, the load-displacement curve, the shear strength, the ultimate displacement, the elastic lateral stiffness, and the energy dissipation. To strengthen the corner joint, an innovative custom-designed hold-down was adopted, and the mechanical performance was also considered. The results showed that the failure of the specimen was mainly due to the yield of the nails and the separation between the stud and the base plate, while the hold-down can greatly improve the shear strength, the ultimate displacement, and the energy dissipation performance of the poplar LVL shear wall without openings. At last, the evaluation formula of the bearing capacity for the light wood shear wall is proposed so as to promote the theoretical basis for the application of poplar LVL in the light wood frame construction.

Effects of Low-Energy-Density Microwave Treatment on Graphene/Polyvinyl Alcohol-Modified Poplar Veneer

The combination of natural wood and graphene can provide a new type of material with excellent mechanical properties and thermal conductivity. However, it is difficult for graphene to uniformly penetrate the wood due to the anisotropy of natural wood and the agglomeration of graphene. In this work, poplar veneer was treated with low-energy-density microwave to expand the entry pathways for the graphene steering liquid. The porosity, weight percent gain, and chromatic aberration were used to examine the impact of the microwave time and power. We tested the mechanical properties, thermal conductivity of the graphene/polyvinyl alcohol-modified poplar veneer to evaluate its properties. At the same time, SEM, XRD, and FT-IR were used to characterize its physical and chemical structure. The results showed that low-energy-density microwave treatment increased the weight percentage gain (WPG) and porosity without affecting the mechanical properties of the poplar veneer. The graphene-modified poplar veneer with the optimal overall performance was obtained by microwave treatment at 100% microwave power for 50 s. Indeed, the micro-characterization also revealed that the microwave treatment mostly attacked the wood rays but had little effect on the materialized structure. Therefore, low-energy-density microwave treatment could be an energy-saving and efficient way to improve graphene-impregnated veneers.

Preparation of Transparent Fast-Growing Poplar Veneers with a Superior Optical Performance, Excellent Mechanical Properties, and Thermal Insulation by Acetylation Modification Using a Green Catalyst.

There has been growing interest in transparent conductive substrates due to the prevailing flexible electron devices and the need for sustainable resources. In this study, we demonstrated a transparent fast-growing poplar veneers prepared by acetylated modification, followed by the infiltration of epoxy resin. The work mainly focused on the effect of acetylation treatment using a green catalyst of 4-Dimethylpyridine on the interface of the bulk fast-growing poplar veneer, and the result indicated that the interface hydrophobicity was greatly enhanced due to the higher substitute of acetyl groups; therefore, the interface compatibility between the cell wall and epoxy resin was improved. The obtained transparent fast-growing poplar veneers, hereafter referred to as TADPV, displayed a superior optical performance and flexibility, in which the light transmittance and haze were 90% and 70% at a wavelength of 550 nm, respectively, and the bending radius and bending angle parallel to grain of TADPV were 2 mm and 130°, respectively. Moreover, the tensile strength and tensile modulus of the TADPV were around 102 MPa and 198 MPa, respectively, which is significantly better than those of the plastic substrates used in flexible electron devices. At the same time, the thermal conductivity tests indicated that TADPV has a low coefficient of thermal conductivity of 0.34 Wm−1 K−1, which can completely meet the needs of transparent conductive substrates. Therefore, the obtained TADPV can be used as a candidate for a flexible transparent substrate of electron devices.

Selected Properties of Plywood Bonded with Low-Density Polyethylene Film from Different Wood Species.

In this work, the effects of wood species and thickness of low-density polyethylene (LDPE) film on the properties of environmentally-friendly plywood were studied. Rotary-cut veneers from four wood species (beech, birch, hornbeam and poplar) and LDPE film of four thicknesses (50, 80, 100 and 150 µm) as an adhesive were used for making plywood samples. The findings of this study demonstrated that plywood samples using all the investigated wood species bonded with LDPE film showed satisfactory physical–mechanical properties. Poplar veneer provided the lowest values for bending strength, modulus of elasticity and thickness swelling of all the plywood samples, but the bonding strength was at the same level as birch and hornbeam veneer. Beech plywood samples had the best mechanical properties. An increase in LDPE film thickness improved the physical–mechanical properties of plastic-bonded plywood.

Laminated wood composite design with improved acoustic properties

Next-generation laminated wood composites were produced using waste poplar (Populus deltoides) veneer and polyvinyl acetate adhesive. Four experimental groups and one control group were created. Ten-layer laminated wood veneer samples were reinforced with natural rubber (Group A), linoleum (Group B), felt (Group C), and elastomeric sponge (Group D); these materials were used in the fifth adhesive layer (middle layer). The sound absorption coefficients of the control and experimental groups were tested via the impedance tube method, according to ASTM standard E1050 (2006). Attention was paid to the acoustic behavior at low frequencies (63 Hz to 250 Hz), mid frequencies (250 Hz to 2000 Hz), and high frequencies (2000 Hz to 6300 Hz). It was determined that the sound absorption coefficient of the experimental groups considerably increased. It can be suggested that the experimental groups be used as sound absorbing acoustic panels and the control group as sound reflective acoustic panels.

Poplar-based thermochromic composites that change colour at 38\xa0\xb0C to 46\xa0\xb0C

The red thermochromic dye (R-TD) is the tetradecanoic acid tetradecyl ester (C28H56O2) and methyl red (C15H15N3O2) mixture that has better permeability enabling its infiltration into wood and better thermochromic properties changing its colour at above 30 °C after about 0.5 min. Thicker poplar-based thermochromic composite specimens (R-PTC, thickness: 5.0 mm) were prepared by filling the R-TD into pre-treated poplar veneer (thickness: 5.0 mm) thus allowing better penetration after pre-treatment. After R-TD infiltration, the R-PTC samples were covered by polypropylene wax for preventing R-TD from overflowing from R-PTC under the action of phase-change temperature. This R-PTC, whose colour can change from light-red to dark-red at 38 °C to 46 °C, can recover to light-red at below 38 °C after about 14 h, and the peak of colour change is at about 42 °C. R-PTC will be suitable for materials used in thermochromic furniture that can indicate the surface temperature to potential users, thus allowing assessment of likely scalded pain when used the furniture.

Static crushing of wood based sandwich composite tubes

This study presents static compression of sandwich tubes for crash applications in the transportation industry. The tubes were made from “I214” poplar veneers for the core, and carbon or glass woven plies reinforced with epoxy resin composites for the skins. The number of I214 layers in the core was varied between 2 and 6 while keeping the same number of plies for the skins. The results reveal interesting energy absorption performance of such structures in static, together with a coupling effect. In comparison with reference, all-carbon tubes, the sandwich tubes with carbon fibre skins having six I214 poplar plies showed an increase in mass of 75.2 g (+271%), a slightly degraded Specific Energy Absorption (- 7.2 J / g, − 10%), and an increase in the energy absorbed (+3,017 J, + 242%). For sandwich tubes with glass fibre skins having six I214 poplar plies, the SEA improved (+16 J / g, + 75%), the energy absorbed increased by 2,192 J (+602%) and the mass increased by 75.3 g (+314%). The SEA levels obtained were of the order of 61.2 J / g for sandwich tubes with carbon fibres and 32.5 J / g for those made of glass fibres (average values from static tests on all configurations).

Study on flame retardant properties of Plywood Made with Eucalyptus, Birch and Poplar Wood

In this work, the laboratory-made flame-retardant polyvinyl alcohol adhesive was used to prepare flame-retardant plywood made with eucalyptus, birch and poplar respectively, and the effect of tree species on the Thermogravimetric behavior and flame-retardant properties of flame-retardant plywood was studied. Thermogravimetric behavior of the flame-retardant plywood prepared by eucalyptus, birch and poplar showed that poplar plywood had highest thermostability.The results of the SBI test are consistent with the results of the LOI test and Thermogravimetric analysis, both indicated that the tree species had a significant effect on the flame-retardant properties of the flame-retardant plywood, the flame-retardant plywood made with poplar veneer has the highest LOI value, lowest HRR value and lowest THR value.

Synergistic catalytic flame retardant effect of zirconium phosphate on the poplar plywood

The layered two dimensional material α-Zirconium Phosphate (α-ZrP) was used to explore its effect on the flame-retardant properties of plywood in this paper. First, the positively charged polyelectrolyte polyethyleneimine (PEI) and the negatively charged polyelectrolyte ammonium polyphosphate (APP) were adsorbed to the surface of poplar veneers through layer-by-layer (LBL) self-assembly technology, then the flame-retardant modified veneer was prepared for use. Followed by, urea formaldehyde (UF) resin composite adhesives with 9%, 15% and 24% mass fractions of α-ZrP were made. The flame-retardant plywood was prepared by modified veneers and composite adhesives. The chemical composition and combustion status of modified veneers were characterized using multiple techniques, including scanning electron microscope (SEM), energy dispersive spectrometer (EDS), attenuated total reflection infrared spectroscopy (ATR-FTIR) and veneer burning experiments. Through the rheological properties and bonding quality test, the appropriate addition amount of α-ZrP was determined to be 15%. The flame retardancy of modified plywood was assessed by the cone calorimeter (CONE). The results showed that the plywood with only UF composite adhesives and the plywood with only flame-retardant veneers have limited ability to inhibit heat release. When flame-retardant veneers were used in conjunction with composite adhesives, the peak Heat Release Rate (pHRR) and Total Heat Release (THR) of the plywood were reduced by 41.8% and 22.9%, respectively, and the ability to suppress heat was significantly improved. In addition, with the introduction of α-ZrP, the total smoke production and the concentration of toxic gas CO were significantly reduced. This showed that when α-ZrP was used in conjunction with APP, α-ZrP has excellent synergistic flame-retardant property on poplar plywood. The research results provide a strong basis for the application of α-ZrP in flame retardancy of the wood based composites.

Study on Properties of Flame-Retardant Plywood Made with Eucalyptus, Birch and Poplar Wood

In this work, the laboratory-made flame-retardant polyvinyl alcohol adhesive was used to prepare flame-retardant plywood made with eucalyptus, birch and poplar respectively, and the effect of tree species on the mechanical properties and flame-retardant properties of flame-retardant plywood was studied. The static bending strength data showed that the tree species had an obvious effect on the mechanical properties of the flame-retardant plywood, the flame-retardant plywood made with eucalyptus had the highest static bending strength, and the sample made with poplar had the lowest static bending strength. The results of the SBI test are consistent with the results of the LOI test, both indicated that the tree species had a significant effect on the flame-retardant properties of the flame-retardant plywood, the flame-retardant plywood made with poplar veneer has the highest LOI value, lowest FIGRA0.2MJ value and lowest THR 600s value.

Comparative investigation into the interfacial adhesion of plywood prepared by air spray atomization and roller coating

Plasma treatment combined with air spray atomization (ASA) can improve the resin spread rate while manufacturing plywood and reduce the manufacturing cost and consumption of chemicals. To provide a mechanistic understanding of the interfacial adhesion of plywood with reduced resin spread rate, plywood prepared by ASA and roller coating (RC) was compared. The obtained results suggest that atomized resin penetrated plasma-treated poplar veneer and resulted in annular filling of vessels. The plasma treatment enhanced the penetration depth of atomized resin and further strengthened the cell walls in the interphase. The reduced elastic modulus (Er) and hardness (H) of the cell wall in plasma-treated ASA interphase were 17.48 GPa and 588.41 MPa, respectively. The plasma treatment further promoted a uniform distribution of shear strain in the shear section of plywood, indicating an enhanced stiffness and load-bearing capacity of the plywood interphase. A comparison between plywood prepared using ASA and RC revealed that massive amounts of resin consumption did not enhance the mechanical properties of the interphase and the resulting plywood. The results reported herein are beneficial for reducing the manufacturing cost and consumption of chemicals. Thus, a relatively sustainable development can be achieved in the wood composites industry.

Utilization of Chinese fast-growing trees and the effect of alternating lamination using mixed-species eucalyptus and poplar veneers

Over the past few decades, the sustainable forest area in China has increased remarkably, with 2400 million cubic meters of eucalyptus produced in 2018 in Guangxi which is the largest plantation area in China. In this study, the effect of alternating lamination using soft poplar veneers and hard eucalyptus veneers, on the mechanical properties of laminated veneer lumber (LVL), was examined. Eucalyptus and poplar veneers were imported from China to Japan to manufacture the LVL. For both eucalyptus and poplar veneers, the pith side (innerwood) sheets were lighter in density than the bark side (outerwood) sheets. The specific Young’s modulus of alternating LVL with hard eucalyptus veneers and soft poplar veneers was smaller than that of the mono-species LVL of eucalyptus and poplar. Strain distributions were obtained with the compression test by using the digital image correlation method. Normal strains showed that the hard eucalyptus layer behaved as a thin plate, whereas the soft poplar layer mitigated the movement of the hard eucalyptus layer. Alternating lamination decreased the variation in the elastic modulus of LVL made from fast-growing species. Therefore, the soft layers mitigated the movement of the hard layers, which had large variations in mechanical properties.

The Effect of Press Temperature and Duration on the Bonding Strength of American Poplar Laminated Veneer Lumber

In this study, the effect of press temperature and duration on bonding strength of laminated veneer lumber (LVL) was investigated. For this purpose, LVLs were produced from I 77/51 American poplar clone (Populus deltoides) by using 2 different press temperatures (140 and 170⁰C) and 3 press duration (10, 15 and 20 minutes). Phenol formaldehyde (PF) adhesive was used for bonding of poplar veneers. The bonding strength and wood failure rate of produced LVLs were determined according to TS EN 314-1 standard. According to experimental results, the LVLs pressed at 170⁰C showed better bonding strength compared to LVLs pressed at 140⁰C. On the other hand, a decrease was observed in the wood failure rate due to the increase in temperature. The highest bonding strength was obtained by press duration of 10 minutes at press temperature of 170⁰C and a significant decrease in bonding strength was observed when press duration was extended.

Effects of the drying process on the shear strength and morphology of the bonding interface of laminated wood

To investigate the influence of the drying process on the bonding properties of laminated wood, a poplar veneer was impregnated with low molecular-weight phenol formaldehyde (PF) resin and laminated wood was created and studied. The effects of drying temperature, drying time and solid content of the PF resin on the moisture content (MC) of the impregnated veneer after drying and the shear strength of the laminated wood were analyzed with an orthogonal experiment. The microscopic mechanism of the bonding performance of the laminated woods was investigated by fluorescence microscopy. The experimental results showed that the higher the PF resin solid content was, the larger the weight gain percentage of the impregnated veneer was. In addition to drying temperature and drying time, the solid content of PF also had a significant influence on the MC of the impregnated veneer after drying. The shear strength of the laminated wood affected by the drying temperature, solid content of PF and drying time and the drying temperature had a more significant effect than the other two factors. The best drying process was a drying temperature of 50 °C, a drying time of 2 h, and a PF solid content of 30%. The fluorescence analysis showed that the shear strength of the laminated wood was affected by the intensity of the PF resin on the bonding interface, and the average and effective penetration depth of the PF resin in the veneer increased with the increase in the drying temperature.