1C-PUR-bonded hardwoods for engineered wood products: influence of selected processing parameters

Luedtke, Jan; Amen, Carlos; Ofen, Albrecht van; Lehringer, Christian

doi:10.1007/s00107-014-0875-8

Cited by 49 publications

(40 citation statements)

References 20 publications

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“…For ash, they found best performance using PRF, whereby a long closed assembly time improved the performance. Using the same primer and a comparable adhesive type, Luedtke et al (2015) found significantly lower delamination for ash (3-5 %), and comparable delamination values for the other wood species using the same primer as used in the present study; however, they applied one instead of three impregnation-drying cycles only.…”

Section: Comparison Of Resultssupporting

confidence: 77%

“…Bernasconi 2004;Ohnesorge et al 2009;Hübner 2009;Schmidt et al 2010;Knorz et al 2014;Ammann et al 2016;Luedtke et al 2015), over the past decades research focus on bonding wood for structural purposes was put almost exclusively on spruce wood. This situation may be influenced by the fact that this wood species represents by far the most important one in the European building sector as indicated by the amount of hardwood consumption in the production of glued laminated timber in Germany, Switzerland and Austria which was less than 1 % in the year 2005 (Ohnesorge et al 2009).…”

Section: Introductionmentioning

confidence: 99%

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Survey of selected adhesive bonding properties of nine European softwood and hardwood species

et al. 2016

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Due to the increasing interest in applying a wider range of wood species for structural purposes, nine European softwood and hardwood species (ash, beech, birch, hornbeam, larch, oak, poplar, black locust and spruce) were assessed for their ability to be bonded with three different commercial adhesive systems (melamineurea-formaldehyde, one-component polyurethane and phenol-resorcinol-formaldehyde). Tensile shear strength and delamination tests were conducted according to European standards, for all tests including the corresponding wood species as adhesive joints and as a solid wood reference. When tested in dry condition, the threshold of solid wood tensile shear strength was reached by all species-adhesive combinations. By contrast, testing in wet condition revealed distinct performance reductions for certain combinations. This trend was confirmed by delamination testing. Overall, the results indicate that extrapolation of test results achieved with a specific wood species (as recommended in the current standard for lapjoint tests) towards other species is highly problematic and has to be done with caution.

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Section: Comparison Of Resultssupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Survey of selected adhesive bonding properties of nine European softwood and hardwood species

et al. 2016

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“…Despite improving strength, the application of the primer did not lead to an improvement in wood failure percentage. Contrary, another study (Lüdtke et al 2015) showed that WFP can be increased by using a primer. This difference may be explained by possible differences in the primer application, or by the small processing window of the primer (Clerc et al 2018).…”

Section: Overall Discussionmentioning

confidence: 91%

Characterization of wood-adhesive bonds in wet conditions by means of nanoindentation and tensile shear strength

Bockel

Harling²,

Grönquist

et al. 2020

Eur. J. Wood Prod.

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The performance of adhesive-hardwood bonds can often be sensitive to humidity and temperature variation. Therefore, it is frequently challenging to achieve standard requirements for structural applications. To gain a better understanding of the wood-adhesive bond, the properties of the individual constituents as well as the local interface of European beech (Fagus sylvatica L.) wood cell walls in contact with structural adhesives were analyzed by means of nanoindentation. These results are compared to classical lap-shear strength. As adhesives two different one-component polyurethane adhesives (1C PUR) and a phenol resorcinol formaldehyde adhesive (PRF) were used. In one case, the beech wood was additionally pre-treated with an adhesion-promoting agent (primer) prior to bonding with 1C PUR. Beech wood joints were analyzed subsequent to several treatments, namely standard climate, after wet storage and in re-dried conditions. In addition, the influence of the primer on the hydroxyl accessibility of beech wood was investigated with dynamic vapor sorption (DVS). The lap-shear strength revealed good performance in dry and re-dried conditions for all adhesives on beech. Both polyurethane adhesives obtained deficits when tested in wet conditions. The use of a primer significantly improved the PUR performance in wet condition. DVS experiment demonstrated a decrease in hydroxyl group accessibility when using a high primer concentration. As novelty, nanoindentation was used for the first time to characterize the local wood-adhesive-interface properties in wet conditions. Nanoindentation showed that all tested 1C PUR perform quite similar in room climate, while PRF achieves considerable higher values for reduced E-modulus and hardness. Wet storage led to a considerable reduction in mechanical properties for all adhesives, while the highest relative change was observed for PRF. After re-drying, the adhesives regained a large part of their original mechanical properties in room climate. No distinct effect of the primer on the local micromechanical properties could be detected with nanoindentation in terms of specific work of indentation.

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“…Recent studies showed that the spread rate of primer application and its concentration are very critical in hardwood bonding and small variations can reduce the primer's effectiveness [4]. Furthermore, the choice of surface preparation can significantly change the bonding performance [5] as well as the primer's efficiency [6]. The 2C PUR system comes with both components separately and is blended only shortly prior to application.…”

Section: Introductionmentioning

confidence: 99%

Modifying elastic modulus of two-component polyurethane adhesive for structural hardwood bonding

Bockel

Harling²,

Konnerth

et al. 2020

J Wood Sci

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Subject to this study is the modification of an experimental two-component polyurethane (2C PUR) as an alternative adhesive for structural hardwood bonding. The 2C PUR has been adapted by calcium carbonate as filler to increase its modulus of elasticity with the aim of increasing the modulus analogue to the ones typically observed for classic amino- and phenol based adhesives. The 2C PUR system was compared with a commercial one-component polyurethane (1C PUR) and a phenol resorcinol formaldehyde (PRF) adhesive. The wetting properties of the adhesives were tested in terms of surface tension, polar and dispersive part and contact angle on European beech wood (Fagus sylvatica L.). In addition, adhesive polymer films of 2C PUR were tested for tensile strength and modulus of elasticity (E-Modulus) following ISO 527-1. The adhesives bond performance on beech wood was determined by lap-joints according to EN 302-1 in various climate conditions. The results show that 2C PUR has proper wettability properties on beech wood. Adding 60% wt filler to the polyol component increased the E-Modulus from 2.3 GPa (0%) to 4.4 GPa. The tensile strength of the modified 2C PUR polymer films was comparable with the industrial 1C PUR. Tensile shear strength and wood failure percentage of 2C PUR lap-joints were increased by adding filler and met requirements in dry and re-dried conditions according to EN 302-1. However, the addition of filler didn’t result in an improvement in wet conditions. The present study shows sufficient performance for bonding hardwood with 2C PUR in dry conditions, while the system still needs to be improvement regarding its performance in humid conditions.

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1C-PUR-bonded hardwoods for engineered wood products: influence of selected processing parameters

Cited by 49 publications

References 20 publications

Survey of selected adhesive bonding properties of nine European softwood and hardwood species

Survey of selected adhesive bonding properties of nine European softwood and hardwood species

Characterization of wood-adhesive bonds in wet conditions by means of nanoindentation and tensile shear strength

Modifying elastic modulus of two-component polyurethane adhesive for structural hardwood bonding

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