The influence of tannin on the improvement of adhesive properties of urea-formaldehyde resin

Abstract

The aim of this study was to examine the properties of urea-formaldehyde (UF) adhesive with the addition of tannin, in order to determine whether it is possible to obtain so-called, bio-adhesives for wood with better mechanical properties compared to commercial UF. Tannin-based UF resins, with four different concentrations of tannin (5, 10, 15, and 20%), were prepared, and adhesive properties were tested and compared with properties of pure UF. Testing of tensile shear strength showed that the addition of tannin in UF adhesive formulation significantly increases its performance compared to pure UF adhesive. It was found that tensile shear strength increased with increasing concentration of tannin, while UF-tannin adhesives with tannin concentrations of 15% and 20% showed higher tensile shear strength than the corresponding pure UF adhesive. Therefore, it can be concluded that tannin-based UF adhesive can be a good candidate for application as an environmentally-friendly wood adhesive due to improvement in terms of adhesive and mechanical properties.