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

Konnerth, Johannes; Kluge, Marcel; Schweizer, Georg; Miljković, Milica; Gindl‐Altmutter, Wolfgang

doi:10.1007/s00107-016-1087-1

Cited by 68 publications

(49 citation statements)

References 23 publications

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“…Lap-shear joints of beech wood demonstrated once again (Konnerth et al 2016;Clerc et al 2018) that the used PRF adhesive is capable of meeting standard requirements for all conditions. However, a formaldehyde free and colorless alternative for safely bonding hardwood is frequently desired.…”

Section: Overall Discussionmentioning

confidence: 92%

“…Adhesive bonding can be one way to enable the use of hardwood for structural applications, thus using hardwood in a more profitable, competitive and sustainable way. However, some hardwood species still show difficulties in meeting requirements for structural standard testing methods, such as delamination resistance according to EN 302-2 (Konnerth et al 2016). While higher strength of hardwood balances positive in wood-engineered products, the response to humidity reduces the competitiveness and potential of some hardwood species (e.g., beech wood).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Overall Discussionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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 lower strength of LPF to PF at high amount of substitution is similar to findings reported in other studies tested in dry and wet conditions . As a matter of course, the absolute performances of the joints are strongly dependent on the wood strength corresponding to treatment . Derived from this, both resins have a low proportion of wood failure (PF: 30%, LPF: 20%) after treatment A2, therefore it can be assumed that the glued joint failed, which causes a stronger drop in strength of LPF.…”

Section: Resultsmentioning

confidence: 99%

Thermoplastic and moisture‐dependent behavior of lignin phenol formaldehyde resins

Solt

Herwijnen

Konnerth

2019

J of Applied Polymer Sci

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Bonding kinetics of thermosetting adhesives is influenced by a variety of factors such as temperature, humidity, and resin properties. A comparison of lignin‐based phenol formaldehyde (LPF) and phenol formaldehyde (PF) adhesive in terms of reactivity and mechanical properties referring to testing conditions (temperature, moisture of specimen) were investigated. For this purpose, two resins were manufactured aiming for similar technological resin properties. The reactivity was evaluated by B‐time measurements at different temperatures and the development of bonding strength at three different conditions, testing immediately after hot pressing, after applying a cooling phase after hot pressing, or sample conditioning at standard climate. In addition, the moisture stability of the two fully cured resins was examined. The calculated reactivity index demonstrated that LPF requires more energy for curing than PF. Further results indicate that lignin as substituent for phenol in PF resin has a negative impact on its moisture resistance. Additionally, the known thermoplastic behavior of lignin could also be detected in the behavior of the cured resin. This behavior is relevant for the adhesive in use and necessitates a cooling phase before testing the bonding strength development of lignin‐based adhesive systems. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48011.

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“…Beech is suggested for the tensile strength test because it has a high average strength of 670 to 770 kg/m 3 and is known to give an average shear strength of 10 MPa to the bond layers as a result (Konnerth et al 2016). Spruce has an average density of 470 kg/m 3 with a lower bond line shear strength (7.5 MPa) than that of beech (Konnerth et al 2006(Konnerth et al , 2016. Prefabricated wood was conditioned in a climate chamber at 20 °C and with a relative humidity of 65% for two weeks before making the specimen.…”

Section: Wood Materialsmentioning

confidence: 99%

Effect of Cellulose Nanofibrils on the Bond Strength of Polyvinyl Acetate and Starch Adhesives for Wood

et al. 2018

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Nanocellulose is a competitive reinforcement material for use in biocomposite structures and fibrous products. In this study, adhesive mixtures of dicarboxylic acid cellulose nanofibrils (CNF) were dispersed into commercial polyvinyl acetate (PVAc) and starch adhesives, which were applied to Norway spruce (Picea abies) to assess their performance in wood joining. Single-lap joints were prepared and tested with PVAc mixtures with 0 to 0.64 wt% CNF and starch glue mixtures containing 0 to 1.07 wt% CNF. CNF suspensions having three concentrations (0.64, 0.96, and 1.28%) were compared. The results showed that the optimum amount of CNF, 0.48% suspensions, added to PVAc increased the average lap joint strength (EN 205:2003) by 74.5% when compared to control specimens with pure PVAc. Correspondingly, 0.96% CNF suspensions also enhanced the strength of starch adhesive by 34.5%. Lower and higher CNF concentrations showed clearly inferior performance.

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

Cited by 68 publications

References 23 publications

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

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

Thermoplastic and moisture‐dependent behavior of lignin phenol formaldehyde resins

Effect of Cellulose Nanofibrils on the Bond Strength of Polyvinyl Acetate and Starch Adhesives for Wood

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