High‐Performance Phenolic Resin Reinforced by Tannic Acid‐Polyethyleneimine Functionalized Multi‐Walled Carbon Nanotubes for Wood‐Based Panels

Phenolic resins play a vital role in wood-based panels for construction materials, but their slow curing rate and limited toughness severely restrict processing efficiency and broader application. Herein, tannic acid (TA), a bioactive macromolecule with a polyphenolic structure, was employed to functionalize multi-walled carbon nanotubes (MWCNTs) through co-deposition with polyethyleneimine (PEI). The tannic acid-polyethyleneimine functionalized multi-walled carbon nanotubes (TA-PEI@MWCNTs) were incorporated as reinforcing fillers into a phenolic resin (PF) matrix to enhance its mechanical properties and curing performance for wood-based panel applications. The resulting TA-PEI@MWCNTs/PF composite exhibited a wet shear strength of 1.5 MPa, reflecting a 24% increase compared to pure PF. This enhancement is attributed to improved interfacial interactions and an increased cross-linking density. Furthermore, the gel time decreased from 360 to 320 s, representing an 11.1% reduction, while the viscosity significantly increased, indicating an accelerated curing process. These improvements stem from chemical interactions among amino groups of PEI, the phenolic hydroxyl groups of TA, and the hydroxymethyl groups of PF, which promote condensation reactions. Micromorphology analysis revealed a tougher fracture surface in the cured TA-PEI@MWCNTs/PF resin, suggesting enhanced energy dissipation. Furthermore, the modified resin demonstrated excellent thermal stability. This study presents an effective approach for developing high-performance tannin-phenolic resin adhesives with strong potential for building composites.