Mechanical Properties of PF and MUF Bonded Juvenile Hybrid Eucalyptus Plywoods Produced in Ghana

To obtain the mechanical properties of plywood produced from six yearold hybrid Eucalyptus in Ghana was the objective of this research. The samples for the experiment were prepared and tested according to GS EN 326-1, GS EN 310, GS EN 314-1, and GS EN 314 -2. The data obtained were analysed using the factorial ANOVA analysis. The mean results obtained for the various treatments were MOE (6520 – 7638 N/mm2), MOR (53.29 – 60.56 N/mm2, shear strength (2.47 – 5.51 N/mm2), failure (72 -90%) and density (725 – 748 kg/m3). The orientation of the surface veneer caused variations among treatments whiles the adhesives PF and MUF largely did not cause any variations among treatments. This study has proven that it is possible to produce sufficiently strong and resistant plywood from the juvenile wood of eucalyptus.

Short notes: The tea leaves as a filler for UF resin plywood production

The addition of green tea leaves fractions < 0.315 mm as a filler to urea-formaldehyde resin to reduction of emission of formaldehyde from three-layer birch plywood was investigated. Moreover, other properties such as bonding quality and water resistance of plywood were investigated. It was found that green tea had an ability to absorb formaldehyde. This phenomenon was caused by phenolic compounds contained in green tea leaves. The addition of green tea in the amount of 20% and 25% resulted in a decrease in formaldehyde emission from plywood comparing to the reference sample. The bonding quality test showed that the addition of tea leaves as a filler did not affect the strength properties of the tested bond lines.

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 grandis and Populus deltoids using 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 MOE were observed for eucalyptus as compare to poplar. Density of ply board was observed as 500-560 kg.m-3 in plywood from poplar and 700-720 kg.m-3 in 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 a phenol-formaldehyde adhesive reinforcement with nanocellulose on the pressing parameters of plywood

Research on improving the reactivity of phenol-formaldehyde (PF) resin and the possibility of lowering the pressing parameters of wood-based materials manufactured with its participation are still progressing. Due to a number of favorable properties, nanocellulose (NCC) is gaining more and more popularity as a modifier of wood adhesives. Therefore, the objective of the study was to assess the possible reduction of plywood pressing parameters due to the reinforcement of PF resin with NCC. Based on the bonding quality results it was found that there is a possibility to reduce pressing time by 25% and pressing temperature by 7%. Moreover, the outcomes of mechanical properties (modulus of elasticity and bending strength) of manufactured plywood indicate that theoretically it could be possible to decrease the pressing parameters even more. However, the shear strength of the glue joints was considered to be a limiting factor for further reduction. The results of delamination test show that plywood bonded with phenolic resin have no tendency to delaminate. Thus, it can be concluded that NCC can be used as a modifier for PF resin which can contribute to the reduction of pressing time and pressing temperature during the plywood manufacturing process.

Properties of the water-resistant plywood glued with pf resin with the addition of tannin filler and nanoclay

The conducted study was aimed at finding the phenol-formaldehyde adhesive formulation containing both the nanoclay and the tannin filler which allows to manufacture water-resistant plywood characterized by the improved properties. The research assumed the application of six experimental variants having a different proportions of the mentioned components which were compared with the mixture prepared according to the industrial recipe. Properties of liquid mixtures such as their gelation time and viscosity were investigated. Moreover, the differential scanning calorimetry (DSC) was performed. The manufactured plywood panels were tested in terms of bonding quality, bending strength and modulus of elasticity. Studies have shown that after the adjustment in components proportions it is possible to achieve the proper viscosity level of adhesive mixtures. The results also indicated that the suitable amount of nanoclay can contribute to the acceleration of resin gel time, however, the DSC analysis showed no effect on its reactivity. The nanoclay concentrations ranging from 2 to 4 pbw (parts by weight) per 100 g of adhesive positively influenced the bonding quality of plywood. Furthermore, there was no clear tendency in case of the effect of applied formulation on the modulus of elasticity and bending strength of plywood. The mixture containing 3 pbw of nanoclay and 5.3 pbw of tannin filler was distinguished as the most beneficial taking into account the improvement in the properties of manufactured plywood.

Effect of open-holes on mechanical properties of wood composite materials

A few variations of open-holes in wood-based pieces, particle board and plywood were modeled in this article. The modulus of elasticity and the coefficient of damping for these pieces were determined using static and dynamic methods and the effect of holes of different quantity and size on mechanical properties were evaluated. As regards to wood particle boards, it was found that the modulus of elasticity decreased to10% after drilling holes, and the coefficient of damping increased to 13%. With regard to plywood pieces these changes were up to 14.5% and up to 21.5%, respectively.

Investigation the fire hazard of plywoods using a cone calorimeter

A high-efficiency fire retardant composition was prepared with dicyandiamide, phosphoric acid, boric acid, borax, urea and magnesium sulfate and it was used to process veneers which were then to prepare the plywood. Meanwhile, heat release and smoke release from combustion of plywood were tested by a cone calorimeter, including heat release rate, mass loss rate, CO yield, CO2 yield and oxygen consumption. Results showed that the plywood with this fire retardant treatment had the better flame-retardant performance and smoke suppression effect as well as the stronger char-forming capability compared to plywood without fire retardant treatment. The average heat release rate, total heat release, average effective heat of combustion, total smoke release, CO yield and oxygen consumption of the plywood with fire retardant treatment were decreased by 63.72%, 91.94%, 53.70%, 76.81%, 84.99% and 91.86%, respectively. Moreover, the fire growth index of plywood treated by fire retardant was relatively low (3.454 kW·m-2·s-1) and it took longer time to reach the peak heat release rate, accompanied with slow fire spreading. The fire performance index was relatively high (0.136 s·m2·kW-1) and it took longer time to be ignited, thus leaving a long time for escaping at fire accidents. The fire hazard of plywood with fire retardant treatment was low, and its safety level was high.

The soy flour as an extender for uf and muf adhesives in birch plywood production

Formaldehyde emission still remains a major disadvantage of widely applied formaldehyde-containing amino resins such as UF (urea-formaldehyde) resin and MUF (melamine-urea-formaldehyde) resin. The compositions of adhesives for plywood manufacturing have to contain a proper extenders in order to adjust their viscosity. Thus, the aim of the study was to investigate the effect of protein-rich soy flour (SF) as the extender for adhesives. The composition of flours and their ability to absorb the formaldehyde were determined. Properties of liquid resins such as gel time, viscosity, pH and solid content were investigated. The possible chemical interaction between the extenders and resins were assessed with the use of FTIR spectroscopy. Plywood panels manufactured using UF and MUF adhesives with the soy flour introduced as the extender in various concentrations were tested in terms of shear strength and formaldehyde release. Studies have shown that soy flour has a favorable composition and formaldehyde-scavenging ability. The addition of SF affected resins properties such as viscosity and gel time but showed no influence on their pH and solid content. FTIR analysis has not explained the chemical interaction between resin and extender. The application of soy flour in the concentration of 15% for UF resin and 10% for MUF resin allowed to produce plywood characterized by improved bonding quality and decreased formaldehyde emission.

Thermoplastic plywood and it’s drawback when moderately heated

GradaTM is new plywood which contains the thermoplastic adhesive. There are so far two material versions 1000 and 2000 which have wide potential in production of wooden products with new perspective of manufacturing. This paper investigates possibilities of including GradaTM material and its versions in skateboard production. Bending strengths at the moderate heat up of this material are presented, specifically at 30, 40°C for both material versions. All increased temperatures are compared to the room temperature (20°C). Mechanical properties that were obtained from the test are modulus of elasticity, modulus of rapture, and stroke strain. The results show the undesirable level of changes present in both versions however version 1000 acts significantly better than 2000.

Longitudinal glued joints of timber beams and the inf luence of quality manufacturing onto their carrying capacity

The content of this article is to analyse destructive testing results of longitudinal solid wood joints of structural size beams with internal and external glued wood-based panels (plywood) stressed in bending, which was mostly focused on simulating the effect of the glued line thickness (1 and 3 mm) and the influence of contact surfaces of longitudinally connected elements when bending loads. The aim of this article is to compare the carrying capacity and the joint real behaviour under load with values obtained using numerical modelling and calculation according to valid standards.

Development of framed poplar plywood for acoustic improvement

Acoustic is a fundamental topic in large environments often characterized by poor sound quality such as dining rooms or open space offices. The paper reports the development and testing of sound absorbing poplar plywood for the acoustic improvement of such spaces; prototypes were designed aiming at acoustic performance and lightness, as an alternative to other acoustic woodbased panels currently on the market. The experimentation ranged from the testing of small specimens to the validation of prototypes in end-use dimensions. Developed panels achieved high sound absorption peaks in the low frequency range (sound absorption coefficient α = 0.80 at frequency of 315 Hz). Prototypes installed on the walls of a dining room reduced significantly its reverberation time (RT60); room users, investigated by a questionnaire, perceived a high acoustic improvement. On the whole the designed products resulted effective sound absorbers; their industrialization can represent a valuable niche for poplar plywood producers.

Characterization of ceiba plywood delamination in mode i using an energetic criterion

To characterize the delamination process of Ceiba plywood, an energy approach was used. This approach considers that crack propagation is a phenomenon of energy dissipation. The fundamental parameter of this approach is the energy release rate (G). To determine this parameter in pure mode I (GI), a Double Cantilever Beam test (DCB) was deployed. The critical energy release rate in pure mode I (GIC) is determined using four approaches, namely Beam Theory, Berry compliance law, Modified Beam Theory and the Compliance Calibration method. Then, a resistance curve of Ceiba plywood was determined according to each approach. Finally, a fracture surfaces analysis was discussed to understand the nature and types of fracture.

Water resistant plywood of increased elasticity produced from European wood species

The paper investigates the possibility of producing the water-resistant plywood of increased elasticity with use of veneers attained from European wood species, such as alder, birch, beech, pine as well as linden, poplar, willow and spruce. Plywood was produced in two variants. Variant I of plywood was made from various wood species, yet the veneers were of the same thickness. In variant II the centre layer in each case was made from 1 mm thick pine veneer and the face layers were made from 1.4 mm thick veneers of various wood species. The produced plywood was subjected to tests on modulus of rupture, modulus of elasticity and tensile strength, bond quality and compression ratio. Specific values of modulus of rupture and modulus of elasticity were also determined taking into consideration the differences in the thickness of applied veneers. Based on these investigations, the authors concluded that, regardless of the manufacturing method, the highest values of modulus of rupture as well as modulus of elasticity and bond quality are achieved for plywood made from linden, poplar, willow and spruce. The change in the plywood structure (variant II) resulted in a considerable decrease in the values of modulus of rupture and modulus of elasticity (and their specific values) both parallel and across the grain. The lowest values of these parameters were obtained for poplar, linden and willow plywood. What is more, as a result of the applied procedure the bond quality of the produced plywood increased and the compression ratio was reduced. Taking the above into account, we can assume that linden, poplar and willow wood is an optimum choice for the face veneers of plywood with increased elasticity. The centre layer of this kind of plywood can be made from pine veneer of lesser thickness.