Morphological Remodeling and Performance of Cured Tannin-Sucrose Adhesive Layer: Enhancement by Catalyst

Abstract

New adhesives were developed using sustainable bayberry tannin and sucrose as raw materials. Through introducing three catalysts—citric acid, p-toluenesulfonic acid, and phytic acid—a comprehensive analysis of their differential impact mechanisms on catalyzing sucrose conversion, promoting cross-linking reactions, and shaping the microstructure of the adhesive was conducted. The results showed that under the phytic acid catalytic system, the yield of 5-hydroxymethylfurfural (5-HMF) reached 17.5 μg/mL, which was higher than that of p-toluenesulfonic acid (14.1 μg/mL) and citric acid (12.9 μg/mL). The introduction of catalysts led to a stepwise improvement in the mechanical properties of the adhesive. The adhesive catalyzed by phytic acid exhibited excellent bonding strength and water resistance, reflecting its advantage in promoting deep cross-linking between 5-HMF and tannin. Scanning electron microscopy results intuitively demonstrated the reshaping of the adhesive layer morphology by the catalysts, evolving from the loose and porous structure of the blank group to a dense, wrinkled morphology after the action of the catalysts. The results of thermogravimetric analysis further quantified the enhancement effect of the catalysts on the thermal stability of the network structure, with the three-dimensional network structure built by the phytic acid system exhibiting superior thermal protection capabilities.