Plywood Panels Research Articles

Synthesis of bio-adhesives from soybean flour and furfural: Relationship between furfural level and sodium hydroxide concentration

Soybean–furfural (SoyFu) adhesives were synthesized through cross-linking soybean flour with furfural under alkaline conditions and the performance of the resulting bio-adhesives was evaluated by manufacturing plywood panels. A total of 30 different bio-adhesive formulations were studied (5 levels of furfural content and 6 levels of sodium hydroxide or pH). Thirty 2-ply plywood panels prepared with these adhesives were pressed at 140°C for 4min. Shear tests were performed on the panels according to ASTM D2339-1998 (2004). The statistical analysis indicated that an interaction existed between furfural (crosslinker) and sodium hydroxide (pH) levels. The best quality panels were produced using adhesives containing high levels of sodium hydroxide (12, 20 and 28g/100g soy flour) and high levels of furfural (50 and 100g/100g soy flour). 13C nuclear magnetic resonance analyses were also performed on a selected formulation. The spectra analysis, however, did not prove that furfural was involved in covalent or ionic bonds with soybean flour.

Thin-folded Shell for the Renewal of Existing Wooden Roofs

ABSTRACTIn this article, a technique for the renewal of historic building wooden roofs is presented. The solution can be used for the strengthening of existing wooden roofs against excessive lateral thrusts on the peripheral wall or for the recovery of the attics, as it allows removing the existing structural elements, such as possible wooden truss-works of no artistic value. With minor adaptations, the solution can be addressed to enhance the building seismic performance. The technique is minimally impairing on existing buildings and can be applied also in new constructions.The technique is based on the construction of a thin folded shell, overlaying the existing pitches. Emphasis is given to lightweight folded shells, obtained by overlaying thin plywood panels on the existing roof rafters and planks, without modifying the overall architectural layout.The technique conceptual design is discussed and a simplified analytical method is proposed, which allows for the clarification of the role of each structural component and can be adopted for the folded shell proportioning and design. The analytical results are validated against numerical results obtained with reference to some case studies. Ultimately, emphasis is given to the detailing, whose correct execution is mandatory for the success of the proposed structural intervention.

Behavior and Strength of Cold-Formed Steel Shear Walls Using Composite Panels

The cold-formed steel (CFS) framed shear wall sheathed with noncombustible panels is an ideal solution for low- and mid-rise buildings when combustible materials are not allowed by the code for certain circumstances. The CFS framed shear wall using steel sheet panel is a commonly used by the industry to fulfill the noncombustible material requirement. However compared to OSB or plywood panels, the steel sheet panel offers significantly lower strength and stiffness. To overcome the disadvantages of steel sheet shear wall, a test program was recently conducted at the University of North Texas to investigate the behavior and strength of CFS steel framed shear wall sheathed with the composite panel which is made of CFS steel sheet bonded to gypsum board. Both monotonic and cyclic tests were performed. It was found that the composite panel provided considerably higher shear strength than the traditional wood based sheathing and the 0.838 mm (0.033 in.) steel sheet sheathing. The composite panel shear wall demonstrated similar failure mechanism and post-peak behavior as the steel sheet shear wall. It is concluded that the tested composite panel is a suitable structural sheathing material for mid-rise buildings, particularly the Type I and II constructions, in seismic areas.

Pullout Performance of Common Construction Fasteners from Long Fiber Thermoplastic Composites

The recent increase in cyclone activity in the last 20 years has pressured the construction industry to look for alternative materials for roof construction. Although plywood is a cheap material, its mechanical properties are highly dependent on moisture content. Long fiber thermoplastics are an emerging type of plastic materials that feature enhanced mechanical properties due to high aspect ratio discontinuous fibers in a tough polymer matrix. The present study focuses on comparing the pullout strength of commonplace fasteners from plywood and long fiber thermoplastic composite panels. Specimens were tested according to ASTM standards D1761-88 and D6117-97 for mechanical fasteners in wood and long fiber thermoplastic (LFT) composites. Common construction nails like 6D, 10D and 16D and a #8 screw were used to compare the performance in terms of withdrawal. The data showed that LFT composites had withdrawal strength on average two to three times that of plywood for all tested fasteners types. Experimental data was analytically verified by APA TT-109 guidelines.

Utilization of waste tire rubber in hybrid plywood composite panel

The aim of this work was to use waste tire rubber (WTR) in the middle layer of hybrid plywood materials. The effects of four variable parameters, namely, WTR contents (430 and 720 g), resin contents (120 and 160 g/m2), hot pressing (single-stage and two-stage), and arrangements of veneer layers on the mechanical, physical, and acoustical properties, were studied. Beech (Fagus orientalis) and alder (Alnus glutinosa) veneers having 1.8-mm thickness were used in the production of hybrid plywood panels. Rubber layers of 3- and 5-mm thickness were used in the middle layer of plywood samples. To produce plywood panels, single-stage and two-stage hot-pressing processes were used. Bonding of wood layers was performed using 120 and 160 g/m2 urea-formaldehyde resins, and to form the rubber layers and bond them to wood layers, methylene diisocyanate resin (150 g/m2) was used. Overall trend showed that with the increase in rubber content, the physical properties (water absorption, thickness swelling, and sound absorption) of the manufactured panels were improved, while the mechanical properties (modulus of rapture, modulus of elasticity, and impact strength) of the panels were reduced. Both physical and mechanical performances of plywood panels were improved with increase in resin content. An increase in the WTR content in plywood improved the composite's acoustical property. The production process of the wood/rubber plywood did not significantly affect their properties. The order of improvement in the physical properties of the panels is rubber content > resin content > arrangement of layers > pressing process. Copyright © 2015 John Wiley & Sons, Ltd.

Study of Bending Strength and Numerical Modeling of Wooden and Plywood Frame Elements

Modern Frame Systems have appeared by development of frame systems due to search for optimum cost and quality of construction, along with the increased number of multi-storey concrete construction today. Although the initial investment costs of the modern frame systems are high, there use has increased 50 100 times with respect to the traditional methods. With the modern frames, reduction or complete elimination of extra operations, such as cutting and sizing on site, have led to savings on workmanship and time. These systems aim at providing wide range of application in a short time by using minimum workmanship and, consequently, maximum number of application. This study explores, experimentally and numerically, the bending strength of wooden and plywood panels most frequently used for the construction today.

An All‐Natural Adhesive for Bonding Wood

AbstractA novel adhesive that is solely based on natural materials of defatted soy flour (SF) and magnesium oxide (MgO) has been investigated for preparation of five‐ply plywood panels. The resulting plywood panels met the industrial water‐resistant requirement for interior plywood. In this study, mechanisms by which an aqueous mixture of SF and MgO served as a strong and water‐resistant adhesive for bonding wood were investigated. SF was first fractionated into soy protein isolates (SPI), a water‐soluble fraction, and insoluble carbohydrates (ICs) that were mixed with MgO, respectively, for preparation of maple laminates. The water resistance of the resulting maple laminates was evaluated by a three‐cycle water‐soaking‐and‐drying (WSAD) test and a two‐cycle boiling‐water test (BWT). The mixture of MgO and the soluble fraction was not able to bond maple veneers together. The shear strengths of the resulting maple laminates before and after WSAD and BWT all had the following order: MgO–SPI > MgO–SF > SF only > MgO–IC. The water solubility of SF in the heat‐cured SF–MgO mixture was much lower than that of the heat‐cured SF. We believe that the low water solubility of SF–MgO and close interactions between MgO and soy proteins instead of soy carbohydrates were responsible for the superior strengths and high water resistance of the soy‐MgO adhesive.

Predicting the sound insulation of plywood panels when treated with decoupled mass loaded barriers

The addition of mass loaded barriers can be used to improve the sound transmission loss properties of lightweight panels. Decoupling of the mass layer from the panel is achieved using a layer of open celled foam. This treatment causes the panel system to exhibit sound transmission loss behaviour that is similar to conventional double leaf walls. The effects of altering the thickness of the decoupling foam layer, the surface density of the barrier, and the attachment between the treatment and the panel were assessed experimentally. Several analytical prediction methods were combined to develop a model for the transmission loss of the treated system. The material properties of the panel and treatment were measured using static and dynamic methods. These measured values were used in the prediction methods. The prediction methods yielded a range of agreements with the experimental results. The quality of agreement was found to depend on the thickness of the foam decoupling layer, the surface density of the barrier layer and most significantly the attachment method.

Behaviour of a birch plywood under various experimental conditions

Liquid Natural Gaz -LNG- carriers must provide cryogenic reliability and safety for at least 40 years. Most of the insulation systems belong to the so-called membrane type, in which the “insulation complex” is composed of a metal membrane as a barrier, a plywood panel, insulation foam and a plywood panel glued to the inner hull. During construction and exploitation at cryogenic temperature, an impact of the membrane may occur and could lead to a LNG leakage. In order to evaluate this risk, and the role of the plywood in the perforation process of the membrane, a series of original impact tests are carried out at room and cryogenic temperatures on metal-plywood samples thanks to a specially designed catapult. In order to obtain a reliable numerical simulation of the impact, a series of impact and out of plane compression tests at room and cryogenic temperatures are carried out. Thanks to a design experiment, we identified the influence of the moisture content, from 2% up to 30%, and of the temperature, from − 173 ∘ C up to +20 ∘ C, on the strain rate sensitivity of the plywood.

The effect of grain direction on lateral nail strength and thermal conductivity of structural plywood panels

The aim of study was to determine the effects of grain direction on the lateral nail strength and thermal conductivity of structural plywood panels. Experiment were made with plywood manufactured from Scots pine, maritime pine and black pine. A rotary peeler with a maximum horizontal holding capacity of 80 cm was used for veneer manufacturing. The highest values of max load (2,17 kN), stiffness (2,52 kN/ mm) and displacement at ultimate load (36,8 mm) were obtained from C1PR group panels manufactured from black pine. Also, it was determined the mechanical properties in perpendicular to grain were higher than those in parallel to grain. The black pine panels gave highest average thermal conductivity value (0,168 W/mK), while that of Scots pine was lowest (0,145 W/mK). Thermal conductivity of panels in perpendicular to the grain of main axis of plywood was always found to be higher than the values obtained from measurements parallel to the grain.

Reinforcement of Lignin-Based Phenol-Formaldehyde Adhesive with Nano-Crystalline Cellulose (NCC): Curing Behavior and Bonding Property of Plywood

The curing behavior of lignin-based phenol-formaldehyde (LPF) resin with different contents of nano-crystalline cellulose (NCC) was studied by differential scanning calorimetry (DSC) at different heating rates (5, 10 and 20&degC/min) and the bonding property was evaluated by the wet shear strength and wood failure of two-ply plywood panels after soaking in water (48 hours at room temperature and followed by 1-hour boiling). The test results indicated that the NCC content had little influence on the peak temperature, activation energy and the total heat of reaction of LPF resin at 5 and 10&degC/min. But at 20&degC/min, LPF0.00% (LPF resin without NCC) showed the highest total heat of reaction, while LPF0.25% (LPF resin containing 0.25% NCC content) and LPF0.50% (LPF resin containing 0.50% NCC content) gave the lowest value. The wet shear strength was affected by the NCC content to a certain extent. With regard to the results of one-way analysis of variance, the bonding quality could be improved by NCC and the optimum NCC content ranged from 0.25% to 0.50%. The wood failure was also affected by the NCC content, but the trend with respect to NCC content was not clear.

Mechanical and Physical Properties of Thermally Modified Plywood and Oriented Strand Board Panels

Abstract Thermal modification can increase resistance to biological degradation, reduce equilibrium moisture content, and improve the dimensional stability of solid wood. In this study, oriented strand board (OSB) and two types of plywood were thermally modified as a posttreatment at 140°C, 150°C, 160°C, 170°C, and 180°C. Plywood moduli of rupture (MOR) and elasticity (MOE) decreased up to 54 and 22 percent, respectively, at the 180°C treatment, while OSB MOR and MOE decreased up to 25 and 4.3 percent, respectively. Internal bond strength of plywood decreased with increasing temperature, while OSB experienced minimal change. Screw-holding strength of all panels was more adversely affected by increasing temperatures than nail-holding strength, with OSB experiencing 17 and 27 percent maximum reductions in nail- and screw-holding strengths, respectively. Thickness swell performance of all panels improved with increasing temperature, with plywood exhibiting 41 and 77 percent improvements at the 160°C and 180°C treatments, respectively. Mass increase (when subjected to a water soak) of OSB decreased 12 percent at the 150°C treatment, after which it increased. These results suggest that thermal modification posttreatments can improve the thickness swell and water absorption performance of plywood and OSB panels. However, some mechanical properties decreased significantly at treatment temperatures exceeding 160°C. The results provide a technical baseline that may help advance thermal modification technology from primarily solid-wood-only applications toward new, high-volume engineered wood markets. With further research, it may be possible to optimize the treatment technique(s) to ensure that the panels retain sufficient mechanical strength for the desired end-use applications.

Improving urea formaldehyde resin properties by glyoxalated soda bagasse lignin

The aim of this research was a reduction of formaldehyde emission and the improvement of the water resistance of urea formaldehyde (UF) resins by incorporating glyoxalated soda bagasse lignin. For this purpose, various contents of unmodified and glyoxalated lignins (10, 15 and 20 %) were added at pH = 7 instead of second urea during the UF resin synthesis. The properties of the resins as well as water absorption, shear strength, and formaldehyde emission of plywood panels made with these adhesives were measured. Among all the resins synthesized, the resin yielding the best results (based on formaldehyde emission and gelation time as well as water absorption, mechanical strength, and formaldehyde content of the associated panels) was selected, and its properties were further analyzed by Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectrometry (FTIR), and X-ray Diffractometry (XRD). The lignin based resins yielded good shear strength of the plywood panels, passing comfortably relevant international standard specifications; the panels also showed lower formaldehyde emission and water absorption when compared to commercial UF adhesives. Based on these findings, it was attempted to improve the performance of soda bagasse lignin in UF resins by glyoxalation. The UF resin containing 15 % glyoxalated lignin (GLUF15) still exhibited less water absorption and formaldehyde release without significant differences in shear strength and physicochemical properties compared to the UF resin control. DSC analysis indicated that in comparison to UF resin the curing process of GLUF resin shifted to lower temperatures. According to the FTIR spectra, by addition of lignin the proportion of C–N bond in methylene linkages decreases when urea is partly replaced by lignin or glyoxalated lignin. XRD analysis indicated that the crystallinity of the UF resins decreased with addition of glyoxalated lignin.

Design of regular and shear-reinforced panel web beams for long-span construction

The design of a 84-m-long 6.7-m-wide one-story residence built on an island off the coast of British Columbia, Canada, presented special timber engineering challenges. To use materials that can be easily transported in pieces and built on-site, panel web beams (PWBs) were developed as main structural components. Two types of PWBs were used. One is the regular PWB built with glulam members as the flanges, plywood panels as the web, and dimension lumber members as the stiffeners. The other is the shear-reinforced PWBs used in regions where design shear forces were excessive. The shear reinforcement consisted of metal sheet plates and steel plate stripes concealed inside the regular PWB. The perimeter steel plate stripes were connected to wood members using timber rivets. The use of both types of PWBs showed the possibility of designing and building wood composite members for long-span construction with small-size materials that can be easily transported to the site.

Nano-engineered plywood panels: Performance properties

Nanotechnology has a huge potential to develop novel wood composites with enhanced properties. Engineering plywood panels having improved physical and mechanical characteristics by nanotechnology was the main goal of this work. Melamine urea formaldehyde resin used to produce plywood panels was reinforced with various nanomaterials at different loading levels. Density, moisture content after submersion, thickness swelling, water absorption, modulus of rupture, modulus of elasticity, bonding strength, and screw withdrawal strength of the plywood panels were carried out according to national or international standard methods. The results obtained in this study showed that nanomaterial reinforcement significantly affected the physical and mechanical characteristics of the plywood panels. The findings indicate that it is possible to produce novel wood composites having improved performance properties by using nanotechnology.

Tannin Adhesive from Stryphnodendron adstringens (Mart.) Coville in Plywood Panels

The aim of this study was to evaluate the technical viability of using tannin adhesives derived from Stryphnodendron adstringens (Mart.) Coville barks in the production of plywood. 0, 25, 50, 75, and 100% tannin-based adhesives (TF) derived from barbatimao barks were combined with commercial phenol-formaldehyde (PF) adhesive. The properties of the adhesives were determined, and plywood was produced. The panels were produced with five crossed layers, an adhesive grammage of 360 g/m² (double line), and an assembly time of 10 min. A pressing cycle at a temperature of 150 °C, specific pressure of 12 kgf/cm², and duration of 10 min was used. With the exception of the parallel modulus of elasticity, panels produced with 25, 50, 75, and 100% barbatimao-derived tannin adhesive met NBR 31:000.05-001/2 standards (ABNT 2001). The tannin barbatimao adhesive proved feasible for use in plywood panels destined for both humid and dry environments.

Performance, Reaction Mechanism, and Characterization of Glyoxal–Monomethylol Urea (G–MMU) Resin

The nonvolatile and nontoxic aldehyde glyoxal (G) was chosen to react with monomethylol urea (MMU) to prepare a glyoxal–monomethylol urea (G–MMU) resin. The basic properties of the resin and bonding strength of bonded plywood panels were tested. The reaction mechanism of the addition of G to MMU was investigated theoretically at the BLYP/DND/COSMO level of quantum chemistry using density functional theory (DFT) method. The results showed that the addition reaction of G with MMU under weakly acidic conditions mainly involves the reactions of MMU with protonated glyoxal (p-G), protonated 2,2-dihydroxyacetaldehyde (p-G1), and protonated bis-hemidiol (p-G2) to form the two important reactive carbocation intermediates C-p-G–MMU and C-p-G1–MMU and the two important hydroxyl compounds N-p-G–MMU and N-p-G1–MMU. The G–MMU resin was characterized by FTIR and 13C NMR spectroscopies, and the results were found to be quite compatible with those obtained by quantum chemical calculations. Based on the theoretical and ex...

Properties of Modified Phenol-Formaldehyde Adhesive for Plywood Panels Manufactured from High Moisture Content Veneer

This paper presents the results of laboratory investigations of bonding high moisture content (15 %) birch veneers (Betula pubescens Ehrh.) with the use of modifi ed phenol-formaldehyde (PF) resin. Wheat starch, rye fl our, resorcinol and phenol-resorcinol-formaldehyde resin were chosen as modifying agents. Dynamic viscosity, hydrogen ions concentration, solid content, curing time, pot life of developed adhesive compositions and shear strength of plywood samples were evaluated. ANOVA analysis has shown that type, mixture and content of modifying agents affect signifi cantly the mechanical performance of plywood panels. The obtained results of shear strength values were above the standard requirements (1 N/mm 2 ), and the properties of samples met the European standard EN 314-2 for gluing quality of class 3 and such plywood panels can be used in exterior conditions.

Effects of veneer drying at high temperature and chemical treatments on equilibrium moisture content of plywood

Moisture content (MC) is one of the most important factors that can affect many physical and mechanical properties of wood and veneers. MC strongly affects the final strength and durability of joints, development of surface checks in the wood and dimensional stability of the bonded assembly. In this study, plywood panels made from Alnus glutinosa (Alder), Fagus orientalis (Beech) and Picea orientalis (Spruce) wood veneers were treated with ammonium acetate, borax and boric acid by using dipping method to test for their equilibrium moisture content (EMC). Borax and boric acid solutions were used for fire-retardancy, and ammonium acetate for reducing formaldehyde emission. Two different veneer drying temperatures (20°C and 180°C) were used to reveal the effects of veneer drying at high temperature on the hygroscopicity of plywood panels. EMC values of alder, beech and spruce panels decreased significantly with veneer drying at high temperature. Picea orientalis (Spruce) plywood panels had the highest EMC values and followed by Alnus glutinosa (Alder) and Fagus orientalis (Beech) panels. EMC values of plywood panels increased significantly for both drying temperatures after ammonium acetate, borax and boric acid treatments.

Some mechanical properties of plywood produced from eucalyptus, beech, and poplar veneer

In this study, we determined the flexural properties and tensile shear strength of five-ply plywood panels produced with eucalyptus (Eucalyptus grandis), beech (Fagus orientalis.), and hybrid poplar (Populus x euramericana) using urea-formaldehyde (UF), melamine-urea-formaldehyde (MUF) and phenol-formaldehyde (PF) adhesives. Flexural properties were tested on both parallel and perpendicular to grain samples. Tensile shear-strength tests were conducted on four glue lines of the plywood panels, and the effects of species of trees, type of adhesives, and direction of load were determined. The results of variance analyses showed that the effects of species of trees, direction of load, and type of adhesive on flexural properties were significant, but it was determined by specific flexural properties that the effect of the type of adhesive was based on the density of the plywood. In addition, as a result of findings, it can be said that specific mechanical properties may be a good predictor for comparative studies.