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:	School of Architecture, Wood and Civil Engineering School of Architecture, Wood and Civil Engineering > Institute for Materials and Wood Technology BFH Centres and strategic thematic fields > BFH Centre for Wood - Resource and Material School of Architecture, Wood and Civil Engineering > Institut for Building Materials and Biobased Products IBBM
Name:	Bockel, S.; Mayer, Ingo; Konnerth, J.; Niemz, Peter; Swaboda, C.; Beyer, M.; Harling, S.; Weiland, G.; Bieri, N. and Pichelin, Frédéric0000-0003-3856-6707
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:	18 Dec 2020 13:29
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