Resource-saving technologies in the production of glued laminated lumber with a glue line of increased strength

One of the main problems of forestry is increased number of fellings and deforestation. Development of promising technologies in woodworking industry is one of the solutions to this problem. These technologies make it possible to reduce the production cost through the use of cheap and non-scarce materials and improve the quality of the resulting products to the level of premium products by improving the quality of the adhesive bond. The aim of the study is to obtain high-quality glued timber from non-grade oak wood (Quercus Robur L.) based on urea formaldehyde (resin, subsequently treated with ultrasound and constant magnetic field. The studies have shown that strength values of the adhesive bond based on the resin, subjected to shear testing along the wood grain, are significantly higher than that of the control specimens obtained using standard technology. Also, additional studies of internal stresses in the glue line and analysis of the microstructure were carried out. They enable obtain an explanation of the strengthening effect of adhesive joint.

Application of Myrcia splendens tannins in the composition of urea-formaldehyde adhesive for sustainable wood bonding

Tannins from Myrcia splendens from the Amazon rainforest were used for the first time in the formulation of a urea-tannin-formaldehyde (UTF) resin. The objective was to evaluate the effect of different tannin proportions on the glue line performance in Pinus sp. woods, glued with UTF adhesive. The tannins were extracted in a water bath, using 1500 mL of water and 100g of dry bark (liquor/bark 15:1), with addition of 3% Na2SO3, at a temperature of 70 °C for three hours. The adhesives formulations were based on the gradual replacement of mass of the urea-formaldehyde (UF) adhesive by tannin powder, totalizing four compositions and one control treatment. UTF adhesives were evaluated for their physicochemical properties, shear bond strength (wet and dry) and wood failure. The addition of M. splendens tannins to the urea formaldehyde adhesive promoted an increase in glue line strength. The proportion of 5.0% of tannins proved to be ideal in the formulation of the UTF adhesive, considering all the parameters evaluated. Thus, this study proves the potential use of Amazonian tannins from Myrcia splendens in the partial composition of more sustainable UTF adhesives.

Parallel Glueline of Withdrawal Capacity for Mengkulang Glulam

The failure modes and load-carrying capacity of timber connection can be predicted using European Yield Model (EYM). In the load-carrying capacity formula, an unknown parameter for Mengkulang Glulam with the bolt as a fastener, is the withdrawal capacity, Fax,Rk (kN). In this research, the withdrawal capacity tests were conducted with respect to the difference in bolt diameter and glue line existences. The results showed the larger diameter 18 mm parallel with the glue line giving the highest withdrawal capacity and resistance when compared to the same diameter without glue line and 14 mm diameter with and without the glue line. Keywords: Engineered Wood Product (EWP); Structural Material; Withdrawal Capacity; European Yield Model (EYM) eISSN: 2398-4287© 2021. The Authors. Published for AMER ABRA cE-Bs by e-International Publishing House, Ltd., UK. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians/Africans/Arabians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning & Surveying, Universiti Teknologi MARA, Malaysia. DOI: https://doi.org/10.21834/ebpj.v6iSI4.3030

BENDING CHARACTERISTICS OF LAMINATED WOOD COMPOSITES CONSTRUCTED WITH BLACK PINE WOOD AND ARAMID FIBER REINFORCED FABRIC

The aim of this study was to determine the 4-point bending strength and modulus of elasticity in bending of Black pine wood laminated materials reinforced with aramid fiber was bonded using epoxy or polyurethane glues separately. The samples were prepared in accordance with the TS 5497 EN 408 (2006). The results of the study determined that the highest value for static bending strength was found in the laminated wood samples (83.94 N.mm-2) that were prepared using inter-layer aramid fiber reinforced polymer (AFRP) and epoxy glue. The highest value of modulus of elasticity in bending was found in the samples prepared with inter-layer epoxy and AFRP (10311.62 N.mm-2). It was observed that the samples parallel to the glue line of the laminated material showed higher performance compared to those perpendicular to the glue line. The data obtained as a result of this study demonstrated that aramid fiber reinforced Black pine wood laminated materials can be used in the building industry as building materials.

Bending Characteristics of Laminated Wood Composites Made of Poplar Wood and GFRP

In this study, 4 layers of 5 mm thick slats obtained by sawing method from poplar wood were used. Plain woven GRFP with low density and grammage of 100 g/m2 (Type 1) and plain woven GRFP with high density and grammage of 200 g/m2 (Type 2) were placed and glued between each layer. Polyvinyl acetate (PVAc-D4), Polyurethane (PU) and dual-component Epoxy (L285-resin and H285-hardener) adhesives were used for gluing the layers. Strength values (bending and modulus of elasticity) between the obtained layers were investigated. As a result of the study, it was determined that epoxy glue has higher strength than polyurethane and polyvinyl acetate glues; Type 2 plain woven fabric has higher strength than Type 1 plain woven fabric; and parallel load to the glue line results in higher performance than perpendicular load to the glue line.

Influence of technological cracks of peeled vener on the shear strength of ultralam bars

The aim of the research is to study the shear strength of laminated veneer lumber (LVL) when working on shear in four different planes. To determine the influence of the presence of technological cracks formed in the peeling process, an experiment was carried out for which four types of samples were used. The load was applied parallel and perpendicular to the glue line and the direction of the peeled veneer fibers. As tests have shown, the technological weakening of peeled veneer reduces the strength properties of a multilayer glued veneer bar, especially for shear along the glue lines and perpendicular to the direction of the peeled veneer fibers, where the maximum number of microcracks is located. The analysis of these microcracks is carried out and their widths are determined. The width of the studied cracks was from 152 to 94 μm. There is no adhesive layer in the microcracks of this building material, which may indicate insufficient wetting of the veneer surface with the adhesive material, or the difficulty of penetration of high-molecular phenol-formaldehyde glue into the cavity of microcracks.

Effect of pH and pH-Shifting on Adhesion Performance and Properties of Lignin-Protein Adhesives

HighlightsLignin improved the wet adhesion strength of soy protein adhesives when pH shifted from 8.5 to 4.5.Lignin increased the water resistance of soy protein adhesives from 5% to 40% at pH 12.Lignin improved the thermal resistance of soy protein adhesives.pH and pH-shifting treatments led to property changes of lignin, soy protein, and lignin-soy protein.Abstract. Concerns about public health and the environment have created strong interest in developing alternative green products. The focus of this research was to study the effect of lignin on soy protein (SP) adhesives under different pH and pH-shifting treatments. Additionally, this research was designed to understand the consequence of pH and pH-shifting treatments on the adhesion performance of SP and lignin-SP (LSP) adhesives as well as the characteristics, solubility, glue line patterns, and physiochemical properties. To study the aggregation, soluble, and denatured stages of protein, the protein solutions were adjusted to pH 4.5, 8.5, and 12, respectively. In addition, the study of pH-shifting treatments was performed at pH 8.5 and 12 to unfold and denature the protein, respectively. The protein structure was then refolded by adjusting the pH to 4.5 in adhesive slurries. The adhesives presented good adhesion performance under dry conditions with wood failure in most treatments, while satisfactory wet adhesion performance was obtained at pH 4.5, 8.5 to 4.5, and 12. Shifting the pH from 8.5 to 4.5 increased the lignin-protein interaction and provided the best improvement in adhesion performance. Lignin strengthened the protein structure, increased the water resistance, and improved the thermal stability of SP adhesives. At an extremely high pH, the water resistance of SP increased from 5% to 40% with the addition of lignin. Lignin showed great potential for increasing the wet strength of SP adhesives. The SP and LSP properties and adhesion performance could be adjusted and improved by pH and pH-shifting processes. Lignin-SP interactions, water resistance, and glue line pattern proved to be significant factors contributing to adhesion performance. Keywords: Adhesive, Lignin, Lignin-protein interactions, pH, pH-Shifting, Protein.

Preparation and characterization of tannin-based adhesives reinforced with cellulose nanofibrils for wood bonding

Adhesives based on vegetable tannins are already a reality in the market. However, their use is still limited due to their low mechanical resistance and weak humidity resistance. Cellulose nanofibrils (CNFs) are being used as reinforcing materials in various composites, resulting in an improvement of mechanical proprieties in general. The objective of this work was to evaluate the incorporation of CNFs in adhesives made of tannins obtained from the Angico tree (Anadenanthera peregrine). Concentrations of nanofibrils at 1, 5, and 10% were added to the adhesives on a dry basis. Tests of viscosity, pH, solids content, and gel time were performed to determine the physical proprieties of the adhesives. The Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Raman spectra measurements were also determined to understand the interaction between tannins and CNFs. Thermogravimetric analyses (TGA) were carried out to determine the thermal resistance of the composite. The FTIR and Raman characterization identified some differences in the peaks in the chemical composition of the adhesives with different percentages of CNFs. The adhesives showed no different decomposition in the thermogravimetric analyses. The shear strength in the glue line of the adhesive with 5% of CNFs in Toona ciliata woods was determined. Among all the adhesives analyzed, the one with 5% of CNFs produced an improvement in the mechanical resistance and humidity resistance on the glue line.