Poplar Veneer Research Articles

Surface properties of novel wood-based reinforced composites manufactured from crushed veneers and phenolic resins

This study was performed to determine the surface properties of novel wood-based reinforced composites made from poplar veneers and phenolic resins. The veneers with different thickness (1.8, 4, 6, 8 mm) were finely crushed and then were impregnated with phenolic resins to achieve different resin loading (12, 14, 18%). Finally, they were laminated or random paved to manufacture novel wood-based reinforced composites with different target densities (0.8-1.1 g cm-3). With increased veneer thickness or resin content, the hardness of novel wood-based reinforced composites decreased and their roughness increased. The increase of density contributed to the increased hardness and decreased roughness. The surface wettability of novel wood-based reinforced composites appeared to be closely related to their surface roughness. There was a negative correlation between contact angle and roughness. The novel wood-based reinforced composites prepared by laminated mat formation showed higher hardness, lower roughness than those by random mat formation. Such data of surface properties can be applied to design the novel wood-based reinforced composites products with desired quality and provide basic information for further panel processing.

Design and mechanical tests of basalt fiber cloth with MAH grafted reinforced bamboo and poplar veneer composite

High performance fibers are widely applied to wood-based composites as reinforcement to improve mechanical performance of composites. Design and mechanical performance tests of basalt fiber cloth reinforced bamboo and poplar veneer (BFRBV) composite are presented in this paper. The fiber surface usually needs to be treated to increase the bonding strength of composites. The optimization scheme of maleic anhydride (MAH) treatment parameters was obtained by orthogonal experiment, namely temperature of 50 °C, time of 3 h and concentration of 0.08 mol/L. The mechanical performance of wood composites treated with three methods of fiber surface treatment, namely no treatment, KH550 treatment and KH550 and MAH co-treatment, was tested. The results indicated that the mechanical performance indexes of BFRBV composite were greatly improved with KH550 and MAH co-treatment. In comparison with no treatment, dry shear strength was improved by 113.3%, wet shear strength by 126.2%, peel rate was reduced from 20.15% to 0, and MOR was improved by 35.4%.

The effect of DMDHEU modification on physical and biological properties of parallel strand lumbers

In this study, the effect of dimethylol dihydroxyethyleneurea (DMDHEU) modification with four different concentration levels on several properties of parallel strand lumbers (PSLs) produced from poplar veneer strands with phenol and melamine formaldehyde adhesives was studied: density, moisture content, water absorption, thickness swelling, dimensional stability, wettability and decay resistance against C. puteana and T. versicolor attacks. Accelareted aging test was conducted in order to evaluate any loss in effectiveness in decay resistance and dimensional stability due to possibility of cleavage of adhesive bonds in lumbers in outdoors. The PSLs produced with modified strands presented higher density and dimensional stability related with their weight gain but lower moisture content, thickness swelling and water absorption than the controls. DMDHEU modification of PSLs was found efficacious in suppressing brown and white rot fungi attacks, but the protective effect was low when lumbers were aged. PSLs manufactured from rotary peeled veneer strands modified with 5% weight gain of DMDHEU and phenol formaldehyde adhesive showed the most promising results for the investigated properties.

Enhancing resin efficiency in plywood production via DBD plasma treatment and atomized air spray of UF resin

Abstract To improve resin efficiency in plywood production, the veneer surface was modified by dielectric barrier discharge (DBD) plasma and the resin was applied by air spray atomization. The droplet size and coverage of resin droplets were evaluated by image analysis. This novel approach improved the resin efficiency. The shear strength of the produced plywood was improved along with a higher gluing speed. The surface energy of poplar veneer altered after plasma treatment, resulting in an increased size of resin droplets and increased resin coverage. Plywood produced at a plasma-processing power of 4.5 kW exhibited the highest shear strength and a 6 kW plasma-processing power did not bring about advantages. Under these circumstances, the lowest amount of resin necessary for fabricating quality products can be reduced to 50 g m−2.

Effect of modified UV-curing ink on the light-induced discoloration of printed veneer.

To reduce the light-induced discoloration of printed veneer, nano-TiO2 and nano-ZnO were chosen to modify red UV ink and yellow UV ink. Relative ink quality of 0.5%, 1.0%, 1.5% and 2.0% of modifier was added to UV ink by stirring. Then the modified UV ink was printed on the surface of poplar veneer. Using a laser particle sizer, UV-Vis spectrophotometer, and colorimeter, physical properties of the modified ink and color differences printed on poplar veneer were studied. Results showed that the average particle size of the UV inks modified by nano-TiO2 decreased a little while the UV inks modified by nano-ZnO had no change. Absorbance of UV ink in the ultraviolet region was increased with the addition of nano-TiO2 or nano-ZnO. Both of nano-TiO2 and nano-ZnO could prevent light-induced discoloration of printed veneer. But when UV ink modified by nano-ZnO was printed on a veneer surface, the color difference was lower than those modified by nano-TiO2. The optimum amount of nano-ZnO in red UV ink was 1.5%, and the ΔE* of the printed veneer was 0.41. Compared with the veneer printed by unmodified red UV ink, ΔE* decreased 78.1%. The optimum amount in yellow UV ink was 0.5%, and the ΔE* of the printed veneer was 3.12. Compared with veneer printed by unmodified yellow UV ink, ΔE* decreased 66.9%.

Influence of veneer thickness, mat formation and resin content on some properties of novel poplar scrimbers

AbstractThick poplar veneers (4–8 mm) have been finely fluffed to manufacture novel scrimbers by two paving ways, namely by random and laminated mat formations. The following properties of the scrimbers were evaluated: modulus of rupture (MOR) via static bending, modulus of elasticity (MOE), compression strength (CS), shear strength (SS), water absorption rate, thickness swelling rate (TSR) and width swelling rate. The results show that utilization of fluffed thicker veneers reduced the mechanical properties to a certain extent. The TSR of the scrimber was first improved and then weakened by increasing the thickness of the veneers. The scrimber prepared from 6-mm-thick veneers showed the best waterproof performance. The random and laminated mat formations affected the surface texture significantly but the mechanical properties and dimensional stability to a lesser extent. With increasing resin content, the waterproof performance of the scrimbers was improved, which was not otherwise expected. The mechanical properties remained essentially unchanged except for the shear strength.

Novel engineered scrimber with outstanding dimensional stability from finely fluffed poplar veneers

The aim of this study is to prepare a novel wood engineered scrimber with outstanding dimensional stability as well as excellent mechanical properties. A novel technique was exploited for preparation of thick finely fluffed poplar veneers (FFPVs). The physical properties of the veneers before and after fluffing process were compared, and the mechanical properties and dimensional stability of the resultant scrimber were also investigated. The results showed that there was a fivefold increase in water absorption rate (WAR) for FFPVs. Correspondingly, compared with traditional scrimber from the veneers without fluffing, the novel scrimber (Nscrimber) from FFPVs had a slight decline in mechanical strength. However, its dimensional stability was significantly improved, where the thickness swelling rate (TSR) decreased by approximate 74%.

Impact Of Heat Treatment On Weight Loss During Combustion Of Laminated Veneer Lumber (LVL)

This study was performed to determine the effects of heat treatment on weight loss during combustion of the laminated wood materials produced from Oriental beech ( Fagus orientalis L.), scotch pine ( Pinus sylvestris L.), sessile oak ( Quercus petraea L.), and poplar ( Populus nigra L.) veneers bonded with PVAc-D 4 , PUR and MF adhesives. For this aim, the weight loss during combustion of the test samples was determined according to ASTM E 160-50. The results of this study indicated that the weight loss percentage was the highest in poplar wood (89.17%), PVAc-D 4 adhesive (89.79%) and control samples (88.69%). In the interaction of the wood materials and type of adhesive, the highest value was measured in poplar+PUR (90.93%), interaction of the wood materials and heat treatment in poplar + control samples (90.87%), in the interaction of the type of adhesive and heat treatment in PVAc-D 4 + 185 °C (91.10%). In the interaction of the wood material, type of adhesive and heat treatment temperature, the highest value was determined in laminated control poplar samples with PUR adhesive (93%), while the lowest in laminated scotch pine samples with MF and heat-treated at 185 °C (81.83%). The use of laminated and heat-treated wood material in places where in high risk of fire, impregnation of wood material with fire-retardant compounds can be suggested.

Improving Bonding Strength of Oven-dried Poplar Veneers Using Atmospheric Cold Plasma Treatment

Poplar veneers are typically oven-dried at high temperatures to shorten the dying period, and thus reduce energy consumption, which also leads to poor bonding strength. In this study, an atmospheric cold plasma system was self-designed to quickly modify the surface of oven-dried poplar veneers (dried at 120 °C, 200 °C, and 240 °C) to yield high bonding strength samples. The physical and chemical properties of treated samples were investigated with an optical contact angle measuring apparatus, fluorescence microscope (FM), and X-ray photoelectron spectroscopy (XPS). The results showed that surface wettability and adhesive permeability of poplar wood veneer were improved after the atmospheric cold plasma treatment. Moreover, the plasma treatment resulted in the incorporation of oxygen-containing groups onto the surface of the oven-dried poplar veneer. For example, the O-C=O group saw its relative content dramatically increase from 1.37% to 13.57%. These effects synergistically resulted in a high increase (76.2%) in bonding strength when using urea-formaldehyde (UF) resin as the adhesive. The plasma modification system used in this study can be utilized at atmospheric pressure, which is easier to realize industrially as compared to using a radio frequency plasma treatment, which is the currently preferred technique.

Effects of Press Parameters on Some Technological Properties of Polystren Composite Plywood

Aim of study: Formaldehyde content of most of resins used in wood based composite production, wood composite materials have been seen a threat on human health and environment. Therefore, numerous studies have been made to develop an effective method to decrease formaldehyde emission from the wood based panels and various methods have been tried. The aim of the study was to investigate those effects of press parameters on some technological properties of polystren composite plywood. Area of study: This study was conducted at the Pilot Facility of Department of Forest Industry Engineering, Karadeniz Technical University in Trabzon, Turkey. Material and Methods: Poplar ( Populus deltoides ) veneers were used to produce polystren composite plywood. Urea-formaldehyde adhesive was used as bonding material for traditional plywood panels. Three different press temperature (130, 140, 150 o C) and pressing time (6, 8, 10 minutes) were chosen as press parameters in the manufacturing of polystren composite plywood. Bonding strength, bending strength, modulus of elasticity, density and equilibrium moisture content of panels were determined according to TS EN 314-1, TS EN 310, TS EN 323 and TS EN 322, respectively. Main results: The experimental results showed that mechanical properties and density of panels generally increased with increasing press temperature and pressing time whereas the equilibrium moisture content of panels decreased. Research highlights: This study showed that polystyrene wastes can be used in plywood manufacturing as an alternative bonding material for interior uses.

Properties of plywood boards composed of thermally modified and non-modified poplar veneer

Possibilities for use of thermally modified poplar veneer were evaluated for the production of plywood boards in industrial conditions. Formats of poplar veneer were treated at temperatures of 190 °C, 200 °C, 210 °C, and 215 °C for 1 h. By combining the treated and non-treated formats of veneer, thirteen different types of board were made. Analyses showed that the examined physical and mechanical properties were influenced by both the type of construction and the applied thermal treatment. Boards composed only of thermally modified veneer achieved the best results regarding moisture absorption and dimensional stability, and boards composed of the combined veneers had better mechanical properties. Treatments at 200 °C and 210 °C proved to be optimal, while the treatment at 215 °C was too harsh and should not be used for the thermal modification of poplar veneer.

Fire performance of poplar and bamboo curtain veneers treated with fire retardants

Bamboo curtain and poplar veneers, which are used as decorative building materials, were impregnated using two types of fire retardants (A and B) at atmospheric pressure in order to investigate fire retardancy using a cone calorimeter. When the impregnation time was longer, the fire retardancy was enhanced in the decorative material samples. When poplar veneer was treated by fire retardant A with impregnation times of 8 h, 16 h, and 24 h, the peak of heat rate release (pk-HRR) decreased by 41%, 51%, and 50%; the total heat release (THR) values decreased by 61%, 69%, and 75%; the total suspended particulates (TSP) values decreased by 90%, 82%, and 72%; and mass residues increased by 39%, 41%, and 43%, respectively. Treated bamboo curtain veneer had a lower fire retardancy when compared to poplar veneer. When bamboo curtain impregnation times were 8 h, 16 h, and 24 h, their pk-HRR values decreased by 37%, 45%, and 51%; the THR values decreased by 32%, 39%, and 44%; the TSP values decreased by 69%, 57%, and 78%; and the mass residues increased by 26%, 28%, and 29%, respectively. The results from this research should help to develop bamboo curtain veneer as an indoor decorative material.

Screw and Nail-Holding Capacities of Combi Plywood Produced From Eucalyptus, Beech and Poplar Veneer

Combi plywood (combination plywood) consists of plywood made of two or more veneer sheets peeled from different species of wood. Combi plywood has some advantages such as its low weight, low cost, satisfactory performance, and the availability of abundant raw materials. In this study, five-ply combi plywood panels were produced from eucalyptus, beech, and poplar using urea formaldehyde adhesive to combine rotary-peeled veneer sheets. Three plywood groups were produced with different combinations, and we investigated the screw withdrawal and nail holding capacity of the combi plywood. In addition, we determined the air-dried density and equilibrium moisture content of the plywood panels that were produced. The test results were analyzed using the SPSS software program. We used the data that were obtained to determine the combi plywood that provided the greatest screw and nail holding capacities. In addition, we investigated the relationship between density and fastener holding capacity.

The Effect of pH on Electroless Ni-Fe-P Alloy Plating on Poplar Veneer

Ni-Fe-P alloy coating was fabricated on poplar veneer substrates by an electroless plating method. The influence of pH on coating structure, elementary composition, thickness, crystal structure, surface resistivity, and magnetism were evaluated. The results indicated that when the plating solution pH was 9.5, the Ni-Fe-P coating had a crystal structure. The coating consisted of lamellar metal particles, and the thickness increased to 111 μm. This plated veneer showed soft magnetic properties. In contrast, when the plating solution pH was 4.5, the Ni-Fe-P coating had mainly an amorphous structure. The coating consisted of spherical metal particles, and the thickness was 67 μm. After 600 °C heat treatment, this plated veneer shifted to a crystalline structure and exhibited soft magnetic properties. In two kinds of plated veneers, the lateral direction resistivity was two times greater than the longitudinal direction resistivity.

SCREW AND NAIL HOLDING PROPERTIES OF PLYWOOD PANELS REINFORCED WITH GLASS FIBER FABRIC

ABSTRACT In this study, plywood and reinforced plywood with glass fiber fabric were produced with rotary peeled poplar veneers using phenol formaldehyde adhesive. Screw and nail holding tests were conducted to obtain the characteristics of the plywood and reinforced plywood boards. One control group and three different test groups were used. The effects of glass fiber fabric on the screw direct withdrawal, screw-head pull-through, and lateral nail resistance were determined. The results of the tests indicated that the reinforced plywood’s resistances to direct withdrawal of the screw, screw-head pull-through, and lateral nail resistance were significantly higher than those of the unreinforced plywood. In addition, reinforcement of the plywood boards provided longer displacement at maximum load.

Physical and Mechanical Properties of Modified Poplar Veneers

To improve the performance and expand applications of poplar plantation wood, modified poplar veneers based on 1-butyl-3-methylchloride ([Bmim]Cl) were studied. Two groups of poplar veneers were impregnated in ionic liquid [Bmim]Cl (group C) and pure water (group B), separately. Techniques such as hot pressing-coagulation and bath-annealing were applied to these two groups to prepare modified samples. The physical and mechanical properties of each group were tested and characterized, using untreated group (A) as the control. The ductility and thickness variation rate of samples in group C were higher than those in group B. The width variation rate of samples in group C was 64% greater than those in group A and 50.4% greater than those in group B. Scanning electron microscopic (SEM) results also showed the plasticity and the improvement in the transverse connection of samples in group C; these results were more obvious than that for samples in group B. The tensile strength and elastic modulus of samples in group C were higher than those of group B. Compared with the control group, the crystallinity index (CrI) of samples in groups B and C was increased and that of group C was the maximum, but the crystal form remained unchanged.

Variation of Density and Dynamic Modulus of Elasticity of Poplar Veneer and Its Impact on Grade Yield

To maximize the value of poplar wood in manufacturing of laminated veneer lumber (LVL), its radial (from pith to bark) and longitudinal (from bottom to top) variations were examined in terms of the density and dynamic modulus of elasticity (ED) of veneer. The veneer sheets were rotary-peeled from seven representative poplar butt bolts (the bottom part of a stem) and seven representative poplar second bolts (the middle part of a stem). A grading strategy for selecting veneer was proposed based on the requirements of LVL products. In this study, the ED value of each poplar veneer sheet was non-destructively measured by the ultrasonic method. The results showed that there was a weak correlation between veneer density and ultrasonic wave velocity. The bolt class (butt or second bolt) did not significantly influence the variation of veneer density and ED. However, the among-bolt variation played a significant role in the variability. A large difference in diameter between two ends of a bolt (i.e. the within-bolt variation) resulted in a low veneer ED. According to the sorting criteria of Chinese Standard “Laminated Veneer Lumber”, the estimated grade yields of the poplar veneer studied were 45.2% for G1, 39.3% for G2, 13.1% for G3, and 2.4% for G4.

Some properties of LVL composed of poplar and beech veneer and possibilities of their application for window frames

The subject of this paper was a research of physical and mechanical properties of LVL composed of peeled poplar veneers in core layers and only outer layers of beech peeled veneers, so as the examination of window frame glue joint strength produced of this material. LVL boards have been hot pressed in industrial conditions, using appropriate phenol formaldehyde (PP) adhesive. Samples for corner window frame glue joint strength testing were glued with PVAc D4 class adhesive. Statistical analysis showed that there were significant differences both in moisture content and density of LVL boards regarding their thickness, while in the case of hardness this difference did not exist. Examinations of LVL glue line shear strength showed that both phenol formaldehyde (PP) and PVAc D4 class adhesives fulfilled standard requirements. The results of corner window frame double tenon glue joint strength produced from combined poplar-beech veneer LVL indicated that such material could be used to produce window frame corner joint, strong enough to withstand the additional load, without an increase of the cross section.

KAYIN VE KAVAK KAPLAMALARIN MELAMİN FORMALDEHİT TUTKALI KULLANILARAK LAMİNE KAPLAMA KERESTE ÜRETİMİNE UYGUNLUĞU

Laminated Veneer Lumber (LVL) has been proven their usefulness and efficiency as framing members (girders, beams, joist, headers, panels, etc.)in construction. Their application and manufacture is limited in Turkey. In this study, four different types of 7-layers LVLs were successfully manufactured using sawed beech (B) and poplar (P) veneers, and melamine formaldehyde (MF) adhesive. In this work, LVLs were formed with two veneers for each surface and three veneers for core layer. Produced four different types of LVL were coded based on the type and location of the veneers. BBBBBBB, BBPPPBB, PPPPPPP and PPBBBPP were called as Group I, Group II, Group III and Group IV, respectively. As physical properties, oven dry specific gravity (SG) and moisture content (MC) were determined according to TS 2472 (1976a) and TS 2471 (1976b) standards. Mechanical properties like glueline shear strength, modulus of rupture (MOR), modulus of elasticity (MOE) and compression strength (CS)(parallel to grain) were also determined according to EN 314-1 (2004),EN310 (1993) and TS 2595 (Anonymous 1977)standards, respectively. Based on this study, the highest strength and SG values were obtained with all beech used veneers (Group I). On the other hand lowest values were recorded with all poplar veneers (Group III). It should be noted that contribution rate of beech veneers in LVL had an increase on both strength and SG values.

Thermo-Vacuum Modification of Poplar Veneers and its Quality Control

Poplar wood is commonly used for many purposes due to its easy machinability, low density, uniform light colour, and relatively low cost. Here, vacuum thermal treatment is proposed for upgrading veneers in the manufacturing of plywood panels with resulting reduced hygroscopicity, improved durability, and dimensional stability. Thirty-eight batch processes with different treatment conditions (temperature ranging from 150 to 240 °C, time from 0.5 to 22.5 h and pressure from 100 to 1000 mbar) were performed to characterize the influence of process parameters on the product properties. Samples were characterized considering their appearance (colour) and their physical (mass loss and equilibrium moisture content), mechanical (bending strength), and chemical (investigated with near infrared spectroscopy (NIR)) properties. The darkening of poplar veneers and the reduction of mechanical strength were observed with increased treatment time and intensity. Mass loss closely correlated with colour change, resulting from chemical changes in wood components. Principal component analysis (PCA) and partial least squares (PLS) were used for evaluation of near infrared spectral data. Both were correlated with several technical properties, and thus NIR allowed the simultaneous prediction of several of these properties. Both colour change and NIR could be used to optimize the thermal treatment of poplar veneers at the industrial scale and for real-time statistical process control.