Low-carbon cork agglomerated materials via chitosan/blocked isocyanate adhesive: Cross-linking mechanism, high performance, and life cycle assessment.

Incorporating natural biological macromolecules to reduce reliance on petroleum-derived adhesives and valorize bio-wastes is a key path for achieving low-carbon manufacturing. However, the inherent hydrophobic barrier of cork restricts the interfacial wetting and penetration of traditional highly polar bio-based adhesives, severely limiting their mechanical performance. To overcome this bottleneck, this study used Chitosan (CS) as the raw material, Blocked Isocyanate (BI) as the efficient crosslinking agent to develop a low-carbon emission composite adhesive and prepared high-performance cork agglomerated materials. The average tensile strength of the materials prepared by this adhesive reached up to 2.21 MPa, which was much higher than the 1.4 MPa stipulated by the international standards ISO 7322:2014. The average initial compression ratio was 6.5%, the average residual compression ratio was 1.42%, the thermal conductivity ranged from 0.076 to 0.094 W/m·K, satisfying the standards of commercial cork flooring and insulation materials. The analysis results revealed that the amino and urethane groups of chitosan reacted with the isocyanate groups to form urea bonds and urethane bonds, achieving strong and durable bonding. The results from the "cradle-to-gate" life cycle assessment (LCA) confirmed that compared with commercial isocyanate adhesives, the CS/BI composite system maintained excellent bonding performance while reducing key environmental loads such as global warming potential (GWP), abiotic depletion potential (ADP), and acidification potential (AP) by 45.3%, 52.6%, and 81.6%, respectively. This study not only revealed the interface bonding mechanism of multi-component composite systems but also provided a promising application prospect for cork agglomerated materials.