Partially replacing polyurethane resins with chitosan in cork agglomerates: Toward biobased, lower-impact and antimicrobial thermosets.

The replacement of fossil-derived binders in cork agglomerates is a challenge in the development of more sustainable cork-based materials. In this study, novel cork-based thermosets were developed by partially replacing the traditional polyurethane (PU) resin with chitosan (5-30 wt% relative to the binder). Thermosets with a biobased content up to 86% were successfully produced by blending all components followed by hot-compression molding, displaying consistent thickness (14.9-15.2 mm) and bulk density (182-188 kg m-3), comparable to industry-standards. All thermosets remained thermally stable up to 250 °C, and the mechanical performance and resilience of the cork thermosets were preserved, with low permanent deformation. All agglomerates retained their hydrophobic nature, as confirmed by water contact angles (110°-125°), and remained intact after prolonged water immersion (56 days), with water uptake reaching up to 470% without compromising structural integrity. Additionally, all thermosets met the boiling water resistance requirement, showing minimal mass loss (<5 wt%). Burial in a compost medium confirmed the material's high stability, even after incorporation of chitosan. Finally, antimicrobial tests indicated that the agglomerates incorporating 30 wt% chitosan exhibited antibacterial activity against Staphylococcus aureus, highlighting the potential of these materials for applications where antimicrobial properties may be advantageous.