Recyclable Epoxy Composites Built with a Biobased Hardener

Fiber reinforced polymer composites (FRPs) are valuable engineering materials, but they pose a host of environmental and economic challenges. Conventional FRPs utilize epoxy matrices that are neither degradable nor reprocessable, and carbon fiber (CF) reinforcements are incredibly energy intensive and expensive to produce, increasing embodied carbon in decommissioned FRPs. To improve their environmental credentials, degradable epoxy matrix materials must be developed, to enable the recovery and reuse of fiber reinforcements. To maintain the value of the fibers, their length and architecture should be maintained post-recycling. In this work, degradable epoxy resins are synthesized utilizing conventional epoxy monomers with a novel biobased hardener, bis(1,3-dioxolan-4-one), bisDOX. These resins are used as matrix materials in FRPs offering outstanding thermomechanical properties. In GFRPs, values for tensile strength and Young’s Modulus reach 289 and 18 MPa, respectively, while in CFRPs the values reach 119 MPa and 28 GPa, making them competitive with conventional FRPs. Epoxy-bisDOX composites can be recycled under mild conditions by using an organocatalyst to break cross-links and solubilize resultant oligomers, enabling the fiber reinforcements to be recovered and reused. The recycled materials show a minimal decline in mechanical performance, creating a circular system as a sustainable alternative to conventional FRPs.