scholarly journals Adhesive-related warping of thin wooden bi-layers

2019 ◽  
Vol 53 (5) ◽  
pp. 1015-1033
Author(s):  
Axel Rindler ◽  
Oliver Vay ◽  
Christian Hansmann ◽  
Johannes Konnerth
Keyword(s):  
Mechanical Properties ◽  
Urea Formaldehyde ◽  
Wood Adhesive ◽  
Wood Products ◽  
Adhesive Systems ◽  
Emulsion Polymer ◽  
Curing Characteristics ◽  
Engineered Wood Products ◽  
Hydrophilic Material ◽  
Identical Material

Abstract Warping of layered wood-based panels is still a challenging problem in the development of thin engineered wood products. Wood as an anisotropic and hydrophilic material tends to change its volume and mechanical properties with changing moisture content. Besides the wood components, also the mechanical properties of certain adhesives are sensitive to moisture changes. A moisture load onto the adhered wood is resulting in different stress and strain states between the adherends. It is expected that adhesives with different moisture-related properties participate differently to this interaction. To observe an adhesive-related warping, thin spruce/HDF (Picea abies and high-density fibreboard) bi-layers with identical material geometries were manufactured under laboratory conditions, using different wood adhesive systems, which are currently used in furniture and flooring industry [polyurethane (PUR), emulsion polymer isocyanate (EPI), polyvinyl acetate (PVAc), urea formaldehyde (UF) and ultra-low emitting formaldehyde amino adhesive (ULEF)]. The bi-layers were exposed to certain relative humidity conditions, and the resulting deformation was measured with a high-precision laser distance detector. Moisture-dependent warping of the bi-layers was obtained in relation to the used adhesive systems. As a result of the study, it can be shown that initial warping after panel manufacturing strongly depends on the adhesive curing characteristics and, especially, on the amount of water that is released into the wood adherend. For the post-setting panel warping, a differentiation into two adhesive groups became visible: rigid and flexible adhesives. Rigid adhesives (UF and ULEF) showed a higher degree of warping compared to the group of flexible adhesives (PUR, EPI and PVAc).

Influence of extender on Thermo-mechanical Properties of melamine-urea-formaldehyde [MUF] for wood adhesive applications

2020 ◽  
Vol 24 ◽  
pp. 2274-2282
Author(s):  
M. Nagamadhu ◽  
S. Ravi Kumar ◽  
R. Suraj ◽  
K.B. Manjunath Iyer ◽  
G.C. Mohan Kumar
Keyword(s):  
Mechanical Properties ◽  
Urea Formaldehyde ◽  
Wood Adhesive

Assessment, Reinforcement and Monitoring of Timber Structures – COST FP1101

2013 ◽  
Vol 778 ◽  
pp. 1037-1040 ◽  
Author(s):  
Bo Kasal
Keyword(s):  
Mechanical Properties ◽  
Wood Products ◽  
European Countries ◽  
Timber Structures ◽  
Cost Action ◽  
Work Plan ◽  
Engineered Wood Products ◽  
Engineered Wood ◽  
The Cost

This paper describes the goals, work plan, organization and results of the COST Action FP 1001 Assessment, Reinforcement and Monitoring of Timber Structures. 21 European countries with over 100 experts participate in the COST Action that started in 2012. The work of the COST FP 1101 is coordinated with the COST FP1004 "Enhance Mechanical properties of Timber, Engineered Wood Products and Timber Structures." This conference is one of the results of the COST action.

scholarly journals Influence of Air Plasma Pretreatments on Mechanical Properties in Metal-Reinforced Laminated Wood

2022 ◽  
Vol 8 ◽  
Author(s):  
Sebastian Dahle ◽  
Kavyashree Srinivasa ◽  
Jure Žigon ◽  
Arnaud Maxime Cheumani Yona ◽  
Georg Avramidis ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Mechanical Performance ◽  
Mechanical Load ◽  
Urea Formaldehyde ◽  
Air Plasma ◽  
Adhesive Systems ◽  
Plasma Treatments ◽  
Structural Applications ◽  
The Impact

The use of wood-based materials in building and construction is constantly increasing as environmental aspects and sustainability gain importance. For structural applications, however, there are many examples where hybrid material systems are needed to fulfil the specific mechanical requirements of the individual application. In particular, metal reinforcements are a common solution to enhance the mechanical properties of a wooden structural element. Metal-reinforced wood components further help to reduce cross-sectional sizes of load-bearing structures, improve the attachment of masonry or other materials, enhance the seismic safety and tremor dissipation capacity, as well as the durability of the structural elements in highly humid environments and under high permanent mechanical load. A critical factor to achieve these benefits, however, is the mechanical joint between the different material classes, namely the wood and metal parts. Currently, this joint is formed using epoxy or polyurethane (PU) adhesives, the former yielding highest mechanical strengths, whereas the latter presents a compromise between mechanical and economical constraints. Regarding sustainability and economic viability, the utilization of different adhesive systems would be preferable, whereas mechanical stabilities yielded for metal-wood joints do not permit for the use of other common adhesive systems in such structural applications. This study extends previous research on the use of non-thermal air plasma pretreatments for the formation of wood-metal joints. The plasma treatments of Norway spruce [Picea abies (L.) Karst.] wood and anodized (E6/EV1) aluminum AlMgSi0.5 (6060) F22 were optimized, using water contact angle measurements to determine the effect and homogeneity of plasma treatments. The adhesive bond strengths of plasma-pretreated and untreated specimens were tested with commercial 2-component epoxy, PU, melamine-urea formaldehyde (MUF), polyvinyl acetate (PVAc), and construction adhesive glue systems. The influence of plasma treatments on the mechanical performance of the compounds was evaluated for one selected glue system via bending strength tests. The impact of the hybrid interface between metal and wood was isolated for the tests by using five-layer laminates from three wood lamellae enclosing two aluminum plates, thereby excluding the influence of congeneric wood-wood bonds. The effect of the plasma treatments is discussed based on the chemical and physical modifications of the substrates and the respective interaction mechanisms with the glue systems.

scholarly journals Tuning the Adhesive Properties of Soy Protein Wood Adhesives with Different Coadjutant Polymers, Nanocellulose and Lignin

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1972
Author(s):  
Milan Podlena ◽  
Martin Böhm ◽  
Daniel Saloni ◽  
Guillermo Velarde ◽  
Carlos Salas
Keyword(s):  
Shear Strength ◽  
Soy Protein ◽  
Urea Formaldehyde ◽  
Hydroxypropyl Methylcellulose ◽  
Cellulose Nanofibrils ◽  
Soy Protein Isolate ◽  
Wood Adhesive ◽  
Wood Products ◽  
Adhesive Properties ◽  
Wood Adhesives

Commercial wood adhesives are based on products that contain formaldehyde; however, environmental and health concerns about formaldehyde emissions from wood products have influenced research and development efforts in order to find alternative, formaldehyde-free products for wood adhesives. In this work, different soy protein-based wood adhesives are proposed, and their performance is compared to commercial urea formaldehyde (UF) adhesive. Soy protein-based wood adhesives were prepared using either soy protein isolate (SPI) or soy protein flour (SF) with different coadjutant polymers: polyethylene oxide (PEO), hydroxypropyl methylcellulose (HPMC), cellulose nanofibrils (CNF) or polyvinyl alcohol (PVA) with and without addition of kraft lignin. The effects of the type of soy protein, solids content, coadjutant polymer and lignin addition were investigated. The wood adhesive formulations were tested on the bonding of hardwood (white maple) and softwood (southern yellow pine) and the dry shear strength of test specimens was measured according to method ASTM D905-08. The adhesive formulations with SPI achieved significantly higher values than those with SF. The dry shear strength of the adhesives varies depending on the coadjutant polymer, the wood species and the addition of lignin.

scholarly journals Low viscosity melamine urea formaldehyde resin as a bulking agent in reducing formaldehyde emission of treated wood

BioResources ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. 2195-2211
Author(s):  
Rabiatol Adawiah Mohd Ali ◽  
Zaidon Ashaari ◽  
Seng Hua Lee ◽  
Mohd Khairun Anwar Uyup ◽  
Edi Suhaimi Bakar ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Dimensional Stability ◽  
Urea Formaldehyde ◽  
Treated Wood ◽  
Physical And Mechanical Properties ◽  
Formaldehyde Emission ◽  
Wood Products ◽  
Formaldehyde Resin ◽  
Low Viscosity ◽  
Resin Impregnation

Melamine urea formaldehyde (MUF) resin impregnation followed by heat compression is a prominent method in improving mechanical properties and dimensional stability of wood. In addition, melamine is reactive to formaldehyde, and therefore able to reduce the free formaldehyde of the treated wood. This study aimed to produce compressed sesenduk (Endospermum diadenum) wood with low formaldehyde emission using low viscosity MUF resin. The effects of treatment efficiency on the physical and mechanical properties of the wood products were evaluated. The experimental design included impregnation of sesenduk strips with 20% and 30% MUF at five different formulations. Then, it was pre-cured at a temperature of 70 °C for 90 min, followed by hot compression at 140 °C with the compression ratio of 80%. The optimum treatment combination was determined through treatability, mechanical strength, dimensional stability, and formaldehyde emission. It was also compared to other treatments, including impregnation without further compression using formulated MUF and commercial MUF. The results revealed that F4 MUF, which consisted of 30% melamine, 50% formaldehyde, and 20% urea, was the optimal MUF formulation that resulted in low formaldehyde emission and acceptable physical and mechanical properties.

scholarly journals Measurement of moisture-related strain in bonded ash depending on adhesive type and glueline thickness

Holzforschung ◽  
2016 ◽  
Vol 70 (2) ◽  
pp. 145-155 ◽  
Author(s):  
Markus Knorz ◽  
Peter Niemz ◽  
Jan-Willem van de Kuilen
Keyword(s):  
High Strain ◽  
Urea Formaldehyde ◽  
Wood Adhesive ◽  
Image Correlation ◽  
Adhesive Bonds ◽  
Mechanical Loads ◽  
Resorcinol Formaldehyde ◽  
Emulsion Polymer ◽  
Distinct Strain ◽  
Adhesive Type

Abstract Structural wood-adhesive bonds (WAB) have to be durable while subjected to considerable stresses caused by mechanical loads and moisture content changes. To better understand the moisture-related durability of WABs, knowledge is important of how moisture changes generate strain in the bond. In this paper, strain on end-grain surfaces of bonded ash specimens was analyzed by means of digital image correlation. Strains were generated by wood shrinkage, and the evaluation was focused on shear strain (SStr). The bond lines were studied depending on the adhesive type – phenol resorcinol formaldehyde (PRF), melamine urea formaldehyde (MUF), polyurethane (PUR), and emulsion polymer isocyanates (EPI). Moreover, three different glueline (GL) thicknesses of MUF were taken into consideration. Comparing the adhesive types, SStr distributions (SStrD) were strongly influenced by adhesive elasticity. MUF and PRF bonds were quite rigid and were associated with pronounced strain amplitudes in and close to the GL together with strain dissipation reaching deep in the wood. PUR and EPI adhesives were more elastic and therefore allowed for smoother strain transition showing less distinct strain peaks. GL thickness had significant impact on SStrD. A high strain level and direct strain transition between adherends was found for the 0.01 mm GL, whereas a pronounced strain decrease was observed in the 0.1 and 0.2 mm GLs. This indicates different stress levels in the wood-adhesive interface dependent on GL thickness.

scholarly journals Properties of High Density Fiberboard Mixed with Poplar Bark

2020 ◽  
Vol 17 (12) ◽  
pp. 1286-1293
Author(s):  
Zoltán PÁSZTORY ◽  
Katalin HALÁSZ ◽  
Zoltán BÖRCSÖK ◽  
Suthon SRIVARO
Keyword(s):  
Mechanical Properties ◽  
Health Risk ◽  
Indoor Air ◽  
Color Change ◽  
Urea Formaldehyde ◽  
Chemical Compounds ◽  
Dry Weight ◽  
Wood Products ◽  
Raw Material ◽  
Formaldehyde Resin

Formaldehyde in the indoor air is one of the chemicals which can cause health risk; therefore, researchers have strived to reduce formaldehyde emissions from different wood products. There are many chemical compounds in bark, including tannins, which can react with formaldehyde. The aim of this study was to reduce the formaldehyde emissions from HDF by mixing poplar bark powder into the raw material. 2, 4, 6, and 8 % (based on dry weight) Populus×euramericana bark was mixed with fibers, and HDF panels were manufactured with urea-formaldehyde resin. Mechanical properties, color change, and formaldehyde release were measured. Contrary to expectations, the mixed bark did not reduce formaldehyde emissions, but the mechanical properties deteriorated due to the bark powder. Formaldehyde emissions were reduced only in the case of 2 % added bark; in cases of 4, 6, and 8 %, the emissions increased.

Microstructure and Quantitative Micromechanical Analysis of Wood Cell–Emulsion Polymer Isocyanate and Urea–Formaldehyde Interphases

2017 ◽  
Vol 23 (3) ◽  
pp. 687-695 ◽  
Author(s):  
Lizhe Qin ◽  
Lanying Lin ◽  
Feng Fu ◽  
Mizi Fan
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Laser Scanning ◽  
Urea Formaldehyde ◽  
Wood Adhesive ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Micromechanical Analysis ◽  
Emulsion Polymer ◽  
Uf Resin

AbstractEmulsion polymer isocyanate (EPI) and urea-formaldehyde (UF) were selected as typical resin systems to investigate the microstructure of wood–adhesive interphases by fluorescence microscopy (FM) and confocal laser scanning microscopy (CLSM). Further, a quantitative micromechanical analysis of the interphases was conducted using nanoindentation. The FM results showed that the UF resin could penetrate the wood to a greater extent than the EPI resin, and that the average penetration depth for these two resin systems was higher in the case of latewood. CLSM allowed visualization of the resin distribution with contrasting colors, showing that the EPI resin could not penetrate the cell wall, whereas UF resin could enter the cell walls. The micromechanical properties of the cell walls were almost unaffected by EPI penetration but were significantly affected by UF penetration, especially in the first cell wall from the glueline. This further confirmed that only cell walls with resin penetration can improve the mechanical properties of the interphase regions.

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