Gursel Colakoglu

A comparative study on some physical and mechanical properties of Laminated Veneer Lumber (LVL) produced from Beech ( Fagus orientalis Lipsky) and Eucalyptus ( Eucalyptus camaldulensis Dehn.) veneers

Laminated Veneer Lumber (LVL) panels made from eucalyptus (Eucalyptus camaldulensis Dehn.) and beech (Fagus orientalis Lipsky.) veneers were tested for physical and mechanical strength properties in this study. Urea formaldehyde (UF) and Polyvinyl acetate (PVA) adhesives were used for eucalyptus LVL panels and UF adhesive for beech LVL panels. The effect of veneer wood species on some physical and mechanical properties was found statistically significant. Also, different glue species caused the differences in strength properties of LVL panels.ZusammenfassungIn diesem Beitrag werden einige physikalische und mechanische Eigenschaften von Schichtholzplatten, hergestellt aus Buchen- (Fagus orientalis Lipsky.) und Eukalyptusfurnieren (Eucalyptus camaldulensis Dehn.) untersucht. Für die Herstellung von Schichtholzplatten wurden die Buchenfurniere mit UF und die Eukalyptusfurniere mit UF und PVA verleimt. Die Ergebnisse zeigen, dass sowohl die Art des Bindemittels als auch die Holzart der Furniere die Eigenschaften der Schichtholzplatten signifikant beeinflussen.

Formaldehyde Emission, Surface Roughness, and Some Properties of Plywood as Function of Veneer Drying Temperature

ABSTRACT The drying of veneer is an essential part of the veneer-producing process to aid the gluing during the manufacture of the plywood and LVL. Determining the optimum veneer drying temperature without loss of bonding strength is also very important from an industrial viewpoint. Increased temperatures are being used in veneer drying to reduce the overall drying time and increase capacity. In this study, 2-mm-thick rotary-cut veneers obtained from alder (Alnus glutinosa barbata) logs were used as materials. After rotary cutting, veneer sheets were classified into four groups and dried at 20, 110, 150, and 180°C. Three-ply and 6-mm-thick plywood panels were manufactured with urea formaldehyde (UF) adhesive. Surface roughness and color variations of veneer sheets and shear strength, bending strength, equilibrium moisture content, and formaldehyde emission of plywood panels were determined based on veneer drying temperatures. According to the results, the smoothest surfaces were obtained for 20°C drying temperature while the highest values of surface roughness were obtained for 180°C. Total color change value (ΔE*) increased linearly with increasing drying temperature. Shear strength values of plywood panels decreased clearly with increasing veneer drying temperature. While the least bending strength mean value was obtained for 20°C drying temperature, no clear difference was found for bending strength of plywood panels manufactured from veneers dried at 110, 150, and 180°C. Equilibrium moisture content (EMC) of plywood panels decreased with increasing veneer drying temperature and as the veneer drying temperature was increased, formaldehyde emission values of plywood panels increased.

Characteristics of plywood panels produced with urea formaldehyde resin (UF) containing borax

The effects of boron treatments on mechanical, biological, and dimensional properties of wood and wood based materials have been widely investigated. The measurement conducted with desicator method (Colak and Colakoglu 2004) showed that formaldehyde emission of plywood panels impregnated with borax decreased. Shear strength, formaldehyde emission, and bending characteristic of plywood panels produced with an adhesive mixture containing borax were examined in this study.

Variations in Bending Strength and Modulus of Elasticity of Spruce and Alder Plywood after Steaming and High Temperature Drying

Veneer logs are generally heated in hot water or steam prior to the cutting process in veneering and plywood manufacturing. For economical reasons, the veneers should be dried quickly and without damage. High temperatures shorten drying times. Besides the benefits of log steaming and quick drying of veneers at high temperatures, these processes can be effective on some mechanical, physical and chemical properties of wood. In this study, the effects of the steaming process on logs and veneer drying temperatures on bending strength and modulus of elasticity (MOE) of plywood panels manufactured from spruce and alder veneers were investigated. For this aim, some parts of both wood species logs were steamed for 12 hours before veneer manufacturing while some parts were used unsteamed. Unsteamed and steamed groups of spruce and alder veneers were dried at 20°C, 110°C and 180°C temperatures. The effect of the steaming process on bending strength and MOE was different depending on the wood species. Bending strength and the MOE values of spruce plywood panels increased while both strength values of alder plywood panels decreased after the steaming process. The highest bending strength and MOE values were obtained at 110°C for alder and at 180°C for spruce plywood panels.

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.

Formaldehyde emission from particleboards manufactured with waste materials from plywood industry

ZusammenfassungPeeling cores, dried veneer residues and plywood edge pieces containing adhesive are used for particleboard production. So, in this study, the effect of waste materials from plywood industry used for particleboard manufacturing on the formaldehyde emission of panels was investigated.

Effects of wood species and adhesive types on the amount of volatile acetic acid of plywood by using desiccator-method

ZusammenfassungThe effects of wood species and adhesive types on the amount of volatile acetic acid and pH values of plywood panels were investigated using high performance liquid chromatography (HPLC). The plywood panels bonded with PF resin emitted more volatile acetic acid than those bonded with UF resins. According to the pH measurement carried out in the absorption solutions for volatile acetic acid emissions, the pH values of beech plywood panels were found to be higher than those of alder plywood panels.

Effects of hardener on some technological properties of particleboard produced from MUF adhesive with low melamine content

Subject Earlier studies indicated that increasing the melamine/urea (M/U) mole ratio from 45:55 to 50:50 improves the water durability of particle. The thickness swelling of the particleboard produced with this resin is considerably reduced. However, the high melamine content in MUF would increase the price of resin. In this study, particleboards were produced at industrial conditions by using MUF resin with M/U ratio 23:77 and with two different hardener types according to the EN 312-5 standards. Tensile strength perpendicular to the surface, thickness swelling, formaldehyde emission (according to the EN 120 and JIS A 5908 Desiccator Method), and volatile acid content of this panels were determined.

The effects of waiting time of alder (Alnus glutinosa subsp. barbata) veneers before drying on shear and bending strength of plywood

(Alnus glutinosa subsp. barbata) veneers before drying, on some properties of plywood, were investigated. Veneers produced at laboratory conditions were divided into four groups considering their waiting time before the drying process. pH and 1% NaOH solubility of these four groups of veneers were determined. No significant differences were found in solubility and pH values obtained from test groups. In addition bending strength, shear strength and formaldehyde emission values of plywood, produced from these veneers, were investigated. While bending strength and formaldehyde emission values of the plywood showed no differences, the shear strength of the plywood produced from veneers immediately dried after production was significantly higher than the one of other groups.

Effect of Manufacturing Factors on Technological Properties of Plywood from Northern Turkey and Suitability of Panels for Use in Shear Walls

AbstractShear walls provide the lateral resistance needed for light-frame wood structures to withstand earthquake and wind loads. When sheathed with wooden structural panels, shear walls can be strong, stiff, and ductile. This is a study on the effect of wood species and drying temperature of veneer on the suitability of plywood for use in shear walls resisting earthquake loads. The highest lateral nail strength values were obtained from plywood panels manufactured from black pine veneers dried at 160°C. Group C (black pine) showed the highest maximum load values and the greatest displacement at ultimate load, whereas Group A (Scots pine) showed the lowest maximum load values and the least displacement at ultimate load. The stiffness values (2.38, 2.52, and 2.28 for Groups C1, C2, and C3, respectively) in Group C were higher than those of the other groups. The results exceeded the values for standards described in National Design Specification for Wood Construction and ISO 16670 and also met the values in...