Influence of wood extractives on two-component polyurethane adhesive for structural hardwood bonding

Bockel, S.; Mayer, Ingo; Konnerth, J.; Niemz, Peter; Swaboda, C.; Beyer, M.; Harling, S.; Weiland, G.; Bieri, N.; Pichelin, Frédéric (2018). Influence of wood extractives on two-component polyurethane adhesive for structural hardwood bonding The Journal of Adhesion, 94(10), pp. 829-845. Taylor & Francis 10.1080/00218464.2017.1389279

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When bonding wood for structural applications, the wood–adhesive bond is influenced by a variety of factors. Besides the physical and mechanical properties of wood species, their chemical composition, e.g. wood extractives, can play a role in bonding wooden surfaces. A two-component polyurethane system (2C PUR) was chosen to better adapt to the current adhesion problem. The influence of extractives on crosslinking was determined by Attenuated Total Reflection-Fourier Transform Infrared Spectrometer (ATR-FTIR) and on the rheological behavior in terms of gel point and storage modulus. Therefore, 2C PUR was mixed with 10% of eight common wood extractives separately. Furthermore, the mechanical properties of beech wood (Fagus sylvatica L.) bonded with extractive enriched adhesive were tested by means of tensile shear strength tests and evaluation of wood failure. These results of ATR-FTIR clearly show that the majority of crosslinking was terminated after 12 hr. Acetic acid and linoleic acid expedited the isocyanate conversion during the first 2.5 hr. The curing in terms of gel point and storage modulus of 2C PUR was accelerated by starch, gallic acid, linoleic acid, and acetic acid. Heptanal, pentanal, 3-carene, and limonene decelerated the curing. All extractives lowered the storage modulus determined after 12 hr. The bonding of beech wood with extractive–adhesive blends showed a slight decrease of the mechanical properties, with the exception of a marginal increase in the case of linoleic acid and pentanal. In summary, it can be said that 2C PUR is sensitive to the influence of wood extractives and can therefore be partly held responsible for adhesion problems occurring when extractives in surface-wide and higher contents are available.

Item Type:

Journal Article (Original Article)

Division/Institute:

BFH Zentren > BFH Zentrum Holz - Ressource und Werkstoff
Department of Architecture, Wood and Civil Engineering
Department of Architecture, Wood and Civil Engineering > Bereich Forschung & Entwicklung, Dienstleistungen und Weiterbildung
Department of Architecture, Wood and Civil Engineering > Bereich Forschung & Entwicklung, Dienstleistungen und Weiterbildung > Institut für Werkstoffe und Holztechnologie

Name:

Bockel, S.; Mayer, Ingo; Konnerth, J.; Niemz, Peter; Swaboda, C.; Beyer, M.; Harling, S.; Weiland, G.; Bieri, N. and Pichelin, Frédéric

Subjects:

Q Science > Q Science (General)
T Technology > T Technology (General)
T Technology > TA Engineering (General). Civil engineering (General)
T Technology > TH Building construction
T Technology > TP Chemical technology

ISSN:

0021-8464

Publisher:

Taylor & Francis

Language:

English

Submitter:

Christelle Ganne-Chédeville

Date Deposited:

07 Apr 2020 11:42

Last Modified:

07 Apr 2020 11:42

Publisher DOI:

10.1080/00218464.2017.1389279

Uncontrolled Keywords:

adhesives for wood polyurethane infrared spectroscopy rheology

ARBOR DOI:

10.24451/arbor.11252

URI:

https://arbor.bfh.ch/id/eprint/11252

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