Preparation and Performance Evaluation of Valonia Tannin-sucrose Wood Adhesive Based on Sucrose Proportion Regulation

Abstract

Valonia tannin, a typical hydrolysable tannin, was used as the raw material and sucrose as the cross-linking agent to investigate the influence of sucrose proportion on the structure and performance of the adhesive. The aim was to evaluate the feasibility of utilizing hydrolysable tannins for wood adhesives. Fourier transform infrared spectroscopy confirmed that valonia tannin belongs to a typical hydrolysable gallotannin, with ester bond linkages and ortho-trisubstituted benzene ring structures present in the molecule. The bonding performance results showed that as the sucrose proportion increased from 66.7% to 100%, the dry strength increased from 1.04 to 1.43 MPa, and the warm-water strength increased from 0.46 to 0.84 MPa, meeting the requirements for Class II plywood specified in the GB/T 17657 (2022) standard. Increasing the sucrose proportion promoted the dehydration of sucrose toward 5-hydroxymethylfurfural, which is proposed to subsequently form a dense three-dimensional cross-linked network with valonia tannin based on our group’s prior condensed-tannin studies, effectively compensating for the deficiencies of hydrolysable tannins in terms of low reactivity and unstable ester bonds. This study provides a theoretical basis and experimental support for the high-value utilization of hydrolysable tannins in the field of wood adhesives.