Mechanical properties of adhesives for bonding wood—

Published Date
September 2013, Vol.45:32–41, doi:10.1016/j.ijadhadh.2013.03.013

Author 

Frank Stoeckel ^a,c

Johannes Konnerth ^b,,

Wolfgang Gindl-Altmutter ^a,b

• aKompetenzzentrum Holz GmbH—Wood K plus, Altenberger Strasse 69, A-4040 Linz, Austria
• bInstitute of Wood Technology and Renewable Materials, Department of Material Science and Process Engineering, BOKU-University of Natural Resources and Life Sciences, Konrad Lorenz Strasse 24, A-3430 Tulln, Austria
• cInstitute for Building Materials, Concrete Construction, Fire Protection and Organic and Wood-based Construction Materials, TU-Braunschweig, Hopfengarten 20, D-38102 Braunschweig, Germany

Accepted 11 March 2013. Available online 10 April 2013. 

Abstract

In this review the current state of the art on mechanical properties of pure wood adhesives is summarised and discussed. Conventionally, mechanical adhesive properties were characterised by means of macroscopic tensile or bending tests of ex-situ cured adhesive films. More recently, nanoindentation was also used to characterise such ex-situ specimens, but more importantly, this method allows the mechanical characterisation of adhesive bond lines in-situ. Mechanical tests reveal high variability between, but notably also within specific groups of adhesives. For example, the modulus of elasticity covers a wide range of more than two magnitudes ranging from 0.1 GPa up to 15 GPa. Significant differences in adhesive stiffness were observed for adhesives intended to be used for solid wood products compared to wood based composite adhesives, the latter showing higher modulus values. In addition to mechanical adhesive properties as such, factors possibly influencing adhesive performance such as temperature, humidity or ageing of the bonds are taken into consideration.

Abbreviations

DMA, Dynamic mechanical analysis

EP, Epoxy adhesives

EPI, Emulsion polymer isocyanates

Er, Reduced elastic modulus

F, Formaldehyde

H, Hardness

MDF, Medium-density fibreboard

MF, Melamine formaldehyde

MOE, Modulus of elasticity

MUF, Melamine urea formaldehyde (higher melamine content)

NI, Nanoindentation

PF, Phenol formaldehyde

pMDI, Polymeric diphenylmethane diisocyanate

PRF, Phenol resorcinol formaldehyde

PUR, Polyurethane

PVAc, Polyvinyl acetate

RF, Resorcinol formaldehyde

UF, Urea formaldehyde

UMF, Urea melamine formaldehyde (lower melamine content)

Keywords

Wood adhesives

Mechanical properties

Nanoindentation

Moisture

Temperature

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