In the last decades, fibers reinforced polymer composites (FRPC) have experienced a continuously rising demand, since they are widely employed in various applications.. Most commonly used matrices are the epoxy thermosets, since they have excellent thermomechanical properties and they are lightweight. 1 However, those materials cannot be reprocessed or recycled at the end of their lifetime, which causes a rapid consumption of fossil-based feedstocks and environmental concerns. Moreover, the permanent cross-linking of the matrix makes very difficult the recovery of the valuable reinforcements inside the composite. 2-3

To overcome these drawbacks, we propose a new bio-based, vitrimer resin for carbon fiber reinforced composites that can be thermally reprocessed multiple times, keeping unaltered its physicochemical properties thanks to the dynamic boronic ester exchange. The new composite materials can also be easily recycled by vitrimer hydrolysis under mild conditions, making possible the full recovery of the carbon fibers contributing to “circular economy”. The developed material is synthetized by the reaction between the epoxidized linseed oil and a diboronic ester dithiol dynamic cross- linker, through a thiol-epoxy “click” reaction. 4-6 Both the syntheses of the cross-linker and the vitrimer have been developed following green chemistry principles. In particular, the synthesis of the new vitrimer takes advantages of a catalyst and is a solvent free process.

1. https://www.grandviewresearch.com/press-release/global-fiber-reinforced-polymer-frp-composites-market

2. Hongwei S., Lin Z., Yeping W., Lixian S., Ming K., Xiuli Z., Mao C., Rapidly reprocessable, degradable epoxy vitrimer and recyclable carbon fiber reinforced thermoset composites relied on high contents of exchangeable aromatic disulfide crosslinks ,

Comp. Part B 199 (2020) 108278

3. Yu-Yao L., Jia H., Yi-D. L., Xiao-Li Z. , Jian-Bing Z., Biobased epoxy vitrimer from epoxidized soybean oil for reprocessable and

recyclable carbon fiber reinforced composite, Comp. Comm.22 (2020) 100445

4. https://www.vitrimat.eu/

5. Zych A, Tellers J, Bertolacci L, Ceseracciu L, Marini L, Mancini G, Athanassiou A. Biobased, Biodegradable, Self-Healing Boronic

Ester Vitrimers from Epoxidized Soybean Oil Acrylate, ACS Appl. Polym. Mater, 2021, 3, 1135−1144.

https://dx.doi.org/10.1021/acsapm.0c01335

6. Chen, Y.; Tang, Z.; Zhang, X.; Liu, Y.; Wu, S.; Guo, B. Covalently Cross-Linked Elastomers with Self- Healing and Malleable Abilities

Enabled by Boronic Ester Bonds. ACS Appl. Mater. Interfaces 2018, 10, 24224−24231.