Properties Of Plywood Research Articles

Properties of Plywood Panels Composed of Thermally Densified and Non-Densified Alder and Birch Veneers

Ukrainian companies mainly use birch in the manufacture of plywood, but species, such as black alder, are not yet widely used in the manufacture of plywood due to their poorer properties. It is well known that thermal compression is often used to improve the properties of solid wood. Good lay-up schemes of veneer can maximize the advantages and minimize the disadvantages of these wood species, and generally improve the utility value of the plywood. This research aimed to develop plywood panels with two wood species and two types of veneer treatments in order to evaluate the influences of different lay-up schemes on the properties of the plywood. Five-layer plywood panels were formed with 16 different lay-up schemes using birch (Betula verrucosa Ehrh.) (B) and black alder (Alnus glutinosa L.) (A) veneers, which were non-densified (N) and thermally densified (D). The different lay-up schemes were used to identify opportunities to improve the mechanical and physical properties of the plywood by replacing the birch veneer in the plywood structure with an alternative alder veneer. The veneer sheets were thermally densified in a laboratory hot press at a temperature of 180 °C and pressure of 2 MPa for 3 min. The conducted study showed that the bending strength, modulus of elasticity and shear strength of mixed-species plywood (BD–AN–AN–AN–BD) increased by up to 31.5%, 34.4% and 16.8%, respectively, in comparison to those properties of alder plywood from non-densified veneer (AN–AN–AN–AN–AN), by positioning alder non-densified veneers in the core layers and birch densified veneers in the outer layers. Moreover, the surface roughness of plywood panels with outer layers of birch veneer was lower than that of panels with outer layers of alder veneer. It was shown that non-treated alder veneer, despite exhibiting somewhat lower strength properties than birch veneer, could be successfully used with proper lay-up schemes in the veneer-based products industry.

COMPARATIVE STUDY ON PHYSICAL-MECHANICAL PROPERTIES OF PLYWOOD PRODUCED FROM EUCALYPTUS GRANDIS AND POPULUS DELTOIDS VENEERS. SHORT NOTES

Nine-ply plywood panels were produced from Eucalyptus grandisand Populus deltoidsusing urea-formaldehyde (UF) and phenol-formaldehyde (PF) adhesives. The physical and mechanical properties,such as moisture content, density, modulus of rupture (MOR) and modulus of elasticity (MOE) of the eucalyptus and poplar boards, were compared in this study. Samples were tested on both,along and across the grain. Higher values of MOR and MOEwere observed foreucalyptus as compare to poplar. Density of ply board was observed as 500-560kg.m-3in plywood from poplar and 700-720 kg.m-3in plywood from eucalyptus species. These differences were attributed to the variation in properties of veneer wood species. The effect of veneer wood species on some physical and mechanical properties of plywood was found statistically different.

The effect of urea-formaldehyde adhesive modification with propylamine on the properties of manufactured plywood

ABSTRACT The aim of the study was to investigate the effect of propylamine addition to urea-formaldehyde resin on the properties of resultant plywood. The research consisted in investigating the properties of both liquid and cured resins, as well as the produced plywood. Studies have shown that the incorporation of propylamine adversely affected reactivity of the adhesive mixtures by increasing their pH. The evaluation of adhesive chemical structure with FTIR spectroscopy showed some slight changes indicating the reaction of formaldehyde with introduced modifier. The addition of propylamine contributed to the considerable reduction of free formaldehyde contained in the cured adhesive. Furthermore, the propylamine was also found to work effectively as a formaldehyde scavenger by significantly reducing the hazardous emission from plywood. However, based on the results of bonding quality, delamination, bending strength and modulus of elasticity it was found that application of propylamine resulted in a noticeable deterioration of plywood properties. Therefore, the amount of introduced modifier should not exceed 1% of solid UF resin.

Physical and Mechanical Properties of Plywood Produced with Thermally Treated Pinus taeda Veneers

Plywood is a structural composite mainly applied in construction. For this purpose, some sort of preservative treatment is recommended to increase its durability. One option of the available treatments is heat treatment, which promotes the modification of the wood properties. This treatment is carried out on the final product (plywood), because it can reduce strength if applied to the veneers. However, no study has proven such a reduction. Therefore, the aim of this work was to evaluate three different temperatures (160 °C, 180 °C and 200 °C) of the heat treatment on the veneer surface and on the physical properties (specific gravity, moisture content and swelling in thickness) and mechanical properties (MOE and MOR in static bending) of Pinus taeda plywood. A reduction was observed in the roughness of the veneer’s surfaces and the total extractives content changed, with a minimum value reached in the 160 °C treatment. The plywood specific gravity initially increased with the heat treatment and did not change at higher temperatures, moisture content reduced, and thickness swelling was not affected. There was no change in the mechanical properties of the plywood, evidencing that the veneer heat treatment does not prejudice mechanically the final product.

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.

Specific Aspects of the Study of the Surface Properties of Plywood

Reducing the toxicity of plywood encourages the use of dry powder mixtures of polyester resin, as its dissolution in organic matter reduces environmental safety. The paper presents the results of studies of free surface energy and its components (polar and dispersed) for plywood, which is made on the basis of polyester resin. The sequences of polarity change and their ratio to the main component of wood after the formation of plywood board at high temperature, which are consistent with the structural and functional features of thermally modified wood. The resulting plywood is characterized by a reduced property of water absorption, because the free surface energy is reduced by 2.3 times and the polarity by 2 times, which is due to the thermal modification of the veneer. Thus, when applying a comprehensive approach to the study of wettability, polarity, interfacial tension, you can choose stable technologies for new wood products and expand its scope.

Eco-friendly bio-based adhesive for plywood from natural rubber latex (NRL)-blended isocyanate cross-linked starch.

Synthetic adhesives used in the production of plywood are a matter of concern because of the emission of carcinogenic gas formaldehyde, increased environmental pollution, and the depletion of fossil fuels. In this study, a bioadhesive composed of natural rubber latex (NRL) and rice starch was developed. However, rice starch has low moisture resistance, resulting in low adhesion. Thus, to enhance the effectiveness of NRL-blended rice starch-based bioadhesive, rice starch was cross-linked with polymeric 4,4″-diphenylmethane diisocyanate (pMDI) resin, which is an environment-friendly, formaldehyde free, and moisture resistant that is highly compatible with starch. The chemical interaction, viscosity, solid content, and gel time of the developed NRL-isocyanate cross-linked rice starch-based bioadhesive was investigated. The efficacy of the formulated bioadhesive was demonstrated by the fabrication of plywood. The presence of isocyanate and urethane capabilities in the bioadhesive formulations was confirmed by Fourier transform infrared spectroscopy (FTIR). The bioadhesive type Iso-A was discovered to have the highest viscosity of 8270mPa.s, whereas Iso-B has the shortest gel time of 3.46min and the highest solid content of 44%; the higher solid content accelerates the gel time. In terms of physical and mechanical properties of plywood, Iso-B has the lowest thickness swelling (TS) value of 13%, lowest water absorption (WA) value of 52% and shear strength value of 1.92MPa, which corresponds to the ISO 12466-2-2007 standard requirements. Based on the results, NRL-blended isocyanate starch-based bioadhesive could be a good potential raw material for eco-friendlyplywood industries with adequate accuracy.

Influence of Lignin Content and Pressing Time on Plywood Properties Bonded with Cold-Setting Adhesive Based on Poly (Vinyl Alcohol), Lignin, and Hexamine

The sustainability, performance, and cost of production in the plywood industry depend on wood adhesives and the hot-pressing process. In this study, a cold-setting plywood adhesive was developed based on polyvinyl alcohol (PVOH), high-purity lignin, and hexamine. The influence of lignin content (10%, 15%, and 20%) and cold-pressing time (3, 6, 12, and 24 h) on cohesion, adhesion, and formaldehyde emission of plywood were investigated through physical, chemical, thermal, and mechanical analyses. The increased lignin addition level lowered the solids content, which resulted in reduced average viscosity of the adhesive. As a result, the cohesion strength of the adhesive formulation with 10% lignin addition was greater than those of 15% and 20% lignin content. Markedly, the adhesive formulation containing a 15% lignin addition level exhibited superior thermo-mechanical properties than the blends with 10% and 20% lignin content. This study showed that 10% and 15% lignin content in the adhesive resulted in better cohesion strength than that with 20% lignin content. However, statistical analysis revealed that the addition of 20% lignin in the adhesive and using a cold-pressing time of 24 h could produce plywood that was comparable to the control polyurethane resins, i.e., dry tensile shear strength (TSS) value of 0.95 MPa, modulus of rupture (MOR) ranging from 35.8 MPa, modulus of elasticity (MOE) values varying from 3980 MPa, and close-to-zero formaldehyde emission (FE) of 0.1 mg/L, which meets the strictest emission standards. This study demonstrated the feasibility of fabricating eco-friendly plywood bonded with PVOH–lignin–hexamine-based adhesive using cold pressing as an alternative to conventional plywood.

Use of Carbon and Basalt Fibers with Adhesives to Improve Physical and Mechanical Properties of Plywood

Currently, wood is presented as an alternative to traditional building materials and to mitigate climate change. Chile is one of the eight largest wood producers in the world; therefore, wood-based products are an easily accessible resource. The aim of this research is to reinforce at laboratory scale plywood panels with basalt and carbon engineer fibers using epoxy resin and polyvinyl acetate as an adhesive system to improve their physical and mechanical properties. Three-point static bending and Janka hardness tests were carried out. The results showed a better performance in the reinforced boards, which showed an increase in Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) properties in the parallel direction of about 48.2% and 52.8%, respectively. Additionally, for the perpendicular direction, there was an increase of 52.0% and 102.9%, respectively. On the other hand, the Fiber Reinforced Polymer (FRP) plywood panels showed an increase of at least 37% on the Janka hardness property, obtaining higher results with the polyvinyl acetate (PVA) adhesive. Finally, FRP–plywood, PVA–BF and PVA–CF may be a new option for composite wood materials, with their ductile behavior and superior mechanical properties, especially in the perpendicular direction, where the increases were greater than those shown in unreinforced plywood.

Characteristic of plywood using wood mahagony bark powder as veneer bonding agent at several storage life

Several barks from certain species, such as mahogany, have a relatively high tannin compound content. These tannin compounds have several hydroxyl groups that can be oxidized to produce radical groups. These radical groups can bind to wood chemical components through bonding mechanisms, such as esterification and phenoxy radicals coupling. The use of oxidized bark as a bonding agent has shown good characteristics of plywood. However, this method will have a problem, in terms of storage life, when being applied at industrial scale. The purpose of this study was to investigate the possible application of oxidized mahagony bark powder as a bonding agent for producing plywood and evaluate the relationship between storage life and the quality of bonding agent stock in the form of oxidized bark powder. The bark powder was oxidized using hydrogen peroxide and a catalyst. The oxidized powder was stored for 0 days, 1 day, 1 week (7 days), and 1 month (30 days) in a tightly closed container before being applied for the plywood manufacture. The tests carried out were physical and mechanical properties of plywood. The results showed that the physical properties of plywood using oxidized mahagony bark powder as a bonding agent with various storage periods have met SNI 5008.2:2016. However, the mechanical properties of the produced plywood were still below the standard. The results indicated that technology for producing plywood using oxidized bark powder is potential for further development

Surface free energy, wettability and bonding of plywood after fire-retardant treatment with various chemicals

Plywood usage has been increasing recently in the building and furniture industry due to its outstanding surface and resistance properties. Although it has many advantages, the flammability of plywood needs to be improved with fire-retardant chemicals. However, these chemicals which improve panels against burning can be differently influenced many properties of panels. This study aimed to investigate the surface roughness, wettability, and surface free energy of the veneers treated with some fire-retardant chemicals and to determine the changes in the mechanical properties of plywood. The beech, poplar, alder, and pine veneers were used as wood species whilst zinc borate, borax, monoammonium phosphate, and ammonium sulfate were used as fire-retardant chemicals in this study. The surface roughness and contact angle measurements were performed to determine the surface properties of veneers, and then the surface free energy values were calculated. The bonding and bending strength of the plywood panels produced from these veneers were determined according to the relevant standards. As a result of the study, the surface free energy values of veneers with lower contact angles and smoother surfaces were found to be higher. It was also determined that the bonding strength values of plywood panels produced from veneers with high surface energies were also high. Generally, the untreated veneers had higher surface free energy values than the treated veneers. Among the fire-retardant chemicals, zinc borate caused the highest surface free energy values in the beech and alder veneers while borax exhibited the highest values in the poplar and pine veneers.

The Impact of Climatic Aging on the Performance Properties of Plywood

The Impact of Climatic Aging on the Performance Properties of Plywood

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.

Properties of Plywood Made from Perforated Veneers

The paper is focused on the bending properties of beech plywood made from veneers with perforations. The modification of the plywood was done by the targeted perforations in veneers used. The perforations were rectangular in shape 5 × 30 mm. There was a gap of 10 mm between the perforations (in each direction) and the perforations in the individual rows were shifted by 10 mm relative to each other. Two structures of lightweight plywood were investigated: sheathed (lightweight type 1) with perforated inner layers sheathed with solid veneer and perforated (lightweight type 2) with perforations in each layer. Bending properties were evaluated by three-point bend testing. The results showed decreased bending strength (MOR) as well as decreased modulus of elasticity in bending (MOE) with reduction of weight. Bending strength (MOR) was reduced by 33 to 57% and modulus of elasticity (MOE) by 13 to 43% compared to standard (non-lightweight) plywood. Bendability of lightweight plywood expressed by the minimum bending radius (Rmin) and the coefficient of bendability (koh) point to a slight decrease in bendability by 1 to 35% compared to standard (non-lightweight) plywood. The benefit of the proposed plywood lightweight constructions is weight reduction by 16.5 to 24.4%.

Influence of Veneer Density on Plywood Thickness and Some Mechanical Properties

Abstract It has been common knowledge that as the density of wood increases, the mechanical properties also improve. In turn, the density of wood depends on many factors, including the wood moisture content, location and cross-section in the trunk, the type of treatment and the parameters of technological processes. There is a great deal of research reported in the scientific literature on the effect of solid wood density on mechanical properties for different wood species as well as for structural timber. However, no research data can be found related investigation of the influence of veneer density on the properties of the birch plywood. In the present study, researching the properties of 7-ply birch plywood (thickness 9 mm), it was concluded that as the density of veneers increases, the bending properties of plywood in the direction of wood fibers (covered veneers) increases. When determining the plywood gluing quality, similar tendencies have been observed. For plywood with a lower density in all veneer plies the gluing quality (tensile-shear test) for perpendicular wood fiber veneers increases in the direction from the symmetry axis or middle veneer to the plywood outer plies, which can be explained by the fact that the outer plies become denser at the time of the hot pressing process. The results of the study will allow birch plywood manufacturers in direct production, sort veneers by density, to produce plywood with very predictable gluing quality, plywood thickness and mechanical properties in bending.

Plywood Made from Plasma-Treated Veneers: Investigation of Performance Differences between Plasma-Pretreated and Untreated Beech Veneers at Comparable Melamine Resin Load

In this study, the dimensional stability and mechanical properties of plywood made from untreated and plasma-pretreated beech veneers were compared. The wood veneers used (native and thermally modified) were impregnated with melamine resin in a simple dipping process prior to plywood production. The duration of the impregnation process was adjusted to give the same melamine resin loading for the different veneer types, with the plasma-pretreated veneers requiring only a fraction of the impregnation time compared with non-plasma-pretreated veneers. With comparable melamine loading, testing of the mechanical properties of the plywood for the different specimen collectives showed significant differences in some cases with respect to compressive strength, bending strength and tensile strength (with the associated moduli of elasticity). For example, it was shown that plywood made from plasma-pretreated native beech veneers shows an increase in bending strength of about 8%, and from plasma-pretreated and thermally modified beech veneers, there is an increase of about 10% compared to the reference.

Veneer and plywood properties of yemane (Gmelina arborea Roxb.) from 3-, 5-, and 7-year-old plantation trees

ABSTRACT Young (3-, 5- and 7-year-old) yemane (Gmelina arborea Roxb.) trees from an industrial tree plantation in Mindanao, Philippines, were studied for their suitability into veneer and plywood production. For each tree, a 4.5-meter log was cut into three 1.5-meter billets for peeling into 0.85-, 2.20- and 2.80-mm veneer thicknesses using a spindleless lathe. Veneer quality was evaluated based on thickness, frequency and depth of lathe checks on the samples. Ten replicates of 3-ply 4.5 mm plywood bonded with phenol formaldehyde were made per age level to determine conformance to standard. Results showed that veneer thickness was higher than the target by 3–22%. Mean frequency of lathe checks ranged from 1 to 10 per 25 mm veneer length, while mean depth ranged from 15 to 60%. The bond strength quality test showed that despite young age, yemane plywood passed the requirement of the PNS ISO 12466-2:2016.

Research of physical and mechanical properties of plywood based on thermally modified veneer

The article presents the results of a study of the physical and mechanical properties of plywood based on thermally modified birch veneer. The implementation of a full-factor experiment in the temperature range from 160 to 200 °C with a duration of 120 to 240 min made it possible to establish the nature of the dependence of the change in strength in static bending and strength in shearing along the adhesive layer on the veneer heat treatment mode. The parameters of veneer heat treatment are determined, which do not lead to a decrease in the strength of plywood, but allow to reduce the indicators of water absorption and swelling by an amount from 20.4 to 33.5%. Plywood based on thermally modified veneer acquires higher strength and water resistance, which significantly expands the scope of application of glued wood based on urea-formaldehyde resins.

Evaluation on mechanical properties of plywood from two fast growing species: Neolamarckia cadamba and Paraserianthes falcataria

Neolamarckia cadamba (Laran@Kelampayan) and Paraserianthes falcataria (Batai) are both fast growing species known to be planted in Malaysia for their high growth rate, therefore made as reforestation species. This study had been done in evaluating the mechanical properties of these species as a new wood material for plywood production as an alternative and discovering used for the depleting supply of big diameter log from virgin forest. The tree samples were harvested from trial plot in UiTM Pahang, Bandar Tun Razak Jengka, Pahang, Malaysia and sent to plywood mills nearby for plywood production. Plywood was composed in five layers and seven layers with 12 mm thickness and used melamine urea formaldehyde (MUF) as their binder based on commercial industry production. Panels were cut and tested according to Japanese Agriculture Standard for plywood (JAS 2014) at Forest Research Institute Malaysia (FRIM), Kepong, Selangor, Malaysia. Based on minimum standard requirement, results show that both species were suitable to be used in plywood production for general use and structural (decorative) purpose. In addition, increased veneer layers were improved the panel strength. This study shows those species had potential to be an alternative wood material for plywood industry in Malaysia thus can reduce independency of wood species from virgin forest.

Impact of High-pressure Impregnation and Fire Protective Coatings on the Reaction to Fire Performance of Birch Plywood

Abstract Birch plywood has a wide range of applications for interior and exterior use. The demand for plywood with improved fire protection properties and good visual appearance is increasing year by year. The impregnation at high pressure of the whole plywood panels is one of the options to achieve it. The aim of this study was to develop good visual looking birch plywood product for interior design purposes as well evaluate different influencing factors to reaction to fire properties of fire-retardant treated birch plywood. This study consists of three parts. At the first stage, high pressure industrially impregnated plywood properties were studied by two influencing factors – distribution of fire retardant in plywood panel plane and sanding process influence on reaction to fire performance of product. At the second stage, seven different industrial finishing systems were selected for covering high-pressure impregnated birch plywood and their effect on fire reaction performance was studied. In addition, two surface coating systems were studied on standard birch plywood substrate. At the third stage, intumescent coating consumption effect on reaction to fire performance was studied. The reaction to fire performance of birch plywood was evaluated by performing a flammability test using the Single Burning Item test according to EN 13823:2010. It was found that high pressure impregnation of plywood cannot ensure even saturation of fire retardant throughout the sheet, which significantly affects the fire performance of product. The impact of different finishing materials to reaction to fire performance has been described by the results of this research.