New Generation of Recyclable High-Performance Biobased Epoxy Thermosets and Composites

There is a growing demand for epoxy thermosets, characterized by reduced toxicity and carcinogenicity, especially for applications requiring high-performance materials. Starting from natural, renewable, and biobased resources, the epoxidized linseed oil was chosen as a monomer to formulate a range of sustainable thermosets by cross-linking it with a specific tailored mixture of potential biobased anhydrides. The designed resins with a biobased organic carbon content varying from 86 to 96% are recyclable and reprocessable and showed storage moduli (E′) values ranging from 2.1 to 3.7 GPa, glass transition ∼114 to 136 °C, and Young's moduli ∼0.61 to 0.78 GPa. Then, carbon fiber-reinforced composites (CFRCs) were produced and tested proving their suitability with stringent environmental conditions, as proved by the results of outgassing tests. The CFRCs showed high-performance characteristics with exceptional stiffness, E′ ∼ 33 GPa, and high glass transition ∼345 °C. Tensile tests highlighted the robust compressive properties yielding an ultimate stress of ∼290 MPa, alongside superior interfacial properties with ILSS ∼ 42 MPa. Remarkably, the developed CFRC exhibited a high moisture resistance, with zero water absorption observed within 24 h and only 0.32% after 25 days of immersion. Furthermore, the composites demonstrated chemical recyclability, further enhancing their sustainability profile.