Eco-friendly and novel tannin-based wood adhesive enhanced with cellulose nanofibrils grafted by hyperbranched polyamides

Abstract

Tannin-based adhesives, as a natural biobased adhesive, have the potential to expand their application in wood industry as substitutes for traditional adhesives. In this study, cellulose nanofibrils and hyperbranched polyamides (HBPA) were studied to address the challenges associated with the low crosslinking degree and poor water resistance characteristics of condensed tannin-based wood adhesives. The modification strategy focuses on grafting oxidized cellulose nanofibrils with hyperbranched polyamides through the Schiff base reaction. Comprehensive analyses, including FTIR, XPS, XRD, and TG, confirm the successful binding of oxidized cellulose nanofibrils with hyperbranched polyamides, demonstrating their potential to enhance the properties of tannin adhesives. Furthermore, the investigation about bonding strength, and water resistance of tannin adhesives reveal significant improvements in the mechanical and water resistance properties through this modification strategy. In particular, the maximum wet shear strength is 0.7 MPa, meeting the requirements for Class II plywood. This study provides valuable insights into improving the performance of tannin adhesives, offering promising implications for broader applications and contributing to eco-friendly practices in the wood industry.