Lignin-melting driven self-bonding: A thermo-chemical strategy for high-performance binderless bamboo composites

Synthetic resin-bonded wood-based panels suffer from formaldehyde emission and dependency on petrochemical adhesives. Herein, we reported a binderless bamboo composite fabricated via thermomechanical-induced self-bonding, wherein the indigenous lignin was activated to serve as an in-situ adhesive phase. Systematically varying hot-pressing temperature, pressure, and holding time revealed that thermally activated lignin flow and in-situ redistribution played important roles in fiber-to-fiber bonding. This interpretation was supported by complementary FTIR, XRD, TG, and SEM analyses, which collectively revealed temperature-dependent chemical transformations, structural changes, thermal stability, and progressive interfacial densification. While appropriate temperature also promoted hydrogen bonding and ether linkage formation without severe hemicellulose degradation. Response surface methodology identified temperature as the most significant factor governing self-bonding quality. Under optimized conditions (157 °C, 52 MPa, 30 min), the binderless composite exhibited flexural strength of 51.8 MPa, 24 h water absorption of 7.8%, and Vickers hardness of 29.1 kgf/mm 2 , outperforming commercial particleboard and MDF standards. Micro-CT confirmed homogeneous density distribution with minimized porosity. This study elucidated the lignin-driven self-bonding mechanism in bamboo and provided a thermochemical consolidation route for fabricating high-performance, formaldehyde-free bio-composites from lignocellulosic residues.