Tannin-Sucrose Adhesive Properties: A Comparison of Bayberry and Acacia Tannins

Abstract

Bayberry tannin and acacia tannin were selected as raw materials to prepare tannin-sucrose adhesives, and their properties were investigated. Fourier transform infrared spectroscopy (FT-IR) analysis results indicated that both bayberry tannin and acacia tannin were condensed tannins, composed of polymerized flavonoid monomer units, with their repeating units often closely connected to the A and B rings of carbohydrates, with bayberry tannin containing relatively more trisubstituted benzene structural units. Hot-pressing temperature was found to have a significant impact on the adhesive performance. When the hot-pressing temperature was set at 215 °C, the bayberry tannin-sucrose adhesive exhibited excellent bonding performance, meeting the strength requirements of Class II plywood in GB/T 17657 (2022) (≥0.70 MPa). Thermogravimetric (TG) test results revealed that the cured product of the bayberry tannin-sucrose adhesive had superior thermal stability. Scanning electron microscopy (SEM) observations showed that the cured product of the acacia tannin-sucrose adhesive had cracking and porosity on the cross-section, while the cured product of the bayberry tannin-sucrose adhesive presented a unique complex wrinkled structure on the cross-section, which endowed it with higher toughness and better environmental resistance.