Tannin-based wood adhesive with good water resistance crosslinked by hexanediamine

As a biomass material, tannins are used in the preparation of wood adhesives, but their poor strength and water resistance has greatly limited their application. Therefore, it is necessary to prepare tannin-based wood adhesives with good water resistance. In the present study, tannin and hexanediamine were simply mixed at room tem-perature to prepare tannin-hexanediamine (TH) adhesive and then used to prepare plywood. Effects of mass ratio of hexanediamine to tannin and pH value of TH adhesive are studied. The results indicating the effects of mass ratio and pH value are apparent on shear strength. When the mass ratio is above 25 % and the pH value is above 9, the plywood shows good water resistance. Fourier transform-infrared (FTIR), X-ray photoelectron spectros-copy (XPS), liquid chromatography-mass spectrometry (LCMS) and X-ray diffraction (XRD) are used to determine the structures of TH adhesive, confirmed the reaction between tannin and hexanediamine to form macromole-cules. Simultaneous thermal analyzer (TG-DSC) and Dynamic mechanical analysis (DMA) are used to analyze the thermal properties, indicate TH resin contains a good storage module and heat resistance. Therefore, with its good shear strength and water resistance, this newly developed tannin-based adhesive has the potential to application in wood-based panel industry, as an alternative of formaldehyde-based adhesive.

Automated summary

In this study, tannin-hexanediamine (TH) adhesive was prepared by simply mixing tannin and hexanediamine and used to make plywood. The effects of the mass ratio of hexanediamine to tannin and the pH value of the TH adhesive on shear strength were investigated. The results showed that the plywood exhibited good water resistance when the mass ratio was above 25% and the pH value was above 9.