Study of adhesive bondlines in modified wood with fluorescence microscopy and X-ray micro-computed tomography

Published Date
International Journal of Adhesion and Adhesives
July 2016, Vol.68:351–358, doi:10.1016/j.ijadhadh.2016.04.006

• Author 

• Alireza Bastani ^a,,
• Stergios Adamopoulos ^b
• Tim Koddenberg ^a
• Holger Militz ^a

• aWood Biology and Wood Products, Burckhardt Institute, Georg-August-University Göttingen, Büsgenweg 4, 37077 Göttingen, Germany
• bDepartment of Forestry and Wood Technology, Linnaeus University, Lückligs plats 1, 351 95 Växjo, Sweden

Accepted 6 April 2016. Available online 13 April 2016. 

Abstract

The quantitative penetration of three coldset wood adhesives [one-component polyurethane (PU), emulsion polymer isocyanate (EPI), poly (vinyl acetate) (PVAc)] under hydraulic pressure into different types of modified wood was studied using fluorescence microscopy and the results were compared to these of a previous study without pressure on adjacent wood samples. The effective penetration (EP) of PU was negatively affected by furfurlylation and NMM modification when pressure was applied. For PVAc, 30% NMM treatment and heat treatment of Scots pine and beech at 210 °C had a negative effect on its EP, but against this the EP of this adhesive increased after heat treatment of beech at 195 °C. In the case of furfurylation, the depth of penetration of all adhesives was less into wood treated with higher concentration of furfuryl alcohol. PU showed a much deeper penetration into NMM-modified and heat-treated wood than the other adhesives with the exception of heat-treated beech at 195 °C. Application of pressure led to rather different results as compared to the EP data when no pressure was applied. The three-dimensional (3D) visualisation of the penetration of PU adhesive into heat-treated Scots pine was also examined by X-ray micro-computed tomography (XµCT). The 3D flow pattern of PU adhesive into heat-treated Scots pine was clearly depicted by XµCT.

Keywords

Modified wood

Adhesive penetration

Bondline

Fluorescence microscopy

X-ray tomography

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