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

abstract

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.

authors

Vasco Valente, Ana C.Q. Silva, Allison Vercasson, Ana C. Barros, Cátia Vieira, Adelaide Almeida, Armando J.D. Silvestre, Carla Vilela, Carmen S.R. Freire

Groups

G4 - Renewable Materials and Circular Economy

Projects

CICECO-Aveiro Institute of Materials R&D Unit Pluriannual Funding (CICECO-Aveiro Institute of Materials)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

PRR CICECO - Instituto de Materiais de Aveiro (Equipar+ CICECO)

Rede Nacional de Ressonância Magnética Nuclear (PTNMR)

acknowledgements

This study was funded by the PRR – Plano de Recuperação e Resiliência and by the NextGenerationEU funds at Universidade de Aveiro, through the scope of the Agenda for Business Innovation “Pacto da Bioeconomia Azul” (Project no. 16 with the application no. C644915664-00000026) and the project CICECO – Aveiro Institute of Materials, UID/50011/2025 (DOI 10.54499/UID/50011/2025) & LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020) & UID/PRR/50011/2025 (DOI 10.54499/UID/PRR/50011/2025), and project Centre for Environmental and Marine Studies (CESAM), UID/50006 + LA/P/0094/2020 (doi.org/10.54499/LA/P/0094/2020), financed by national funds through the FCT/MCTES (PIDDAC). The NMR spectrometers are part of the National NMR Network (PTNMR) and are partially supported by Infrastructure Project N° 022161 (co-financed by FEDER through COMPETE 2020, POCI, and PORL and FCT through PIDDAC). The authors acknowledge the support of Amorim Cork Solutions, which provided the cork and resin materials and assisted throughout the experimental testing, thereby contributing to the development of this research.