A Strong and Tough Thermosetting Epoxy Resin for Recyclable High-Performance Composites

Epoxy-based carbon fiber-reinforced composites (EP-CFRCs) are appealing for engineering applications due to their exceptional specific strength and modulus. Nevertheless, the intrinsic brittleness and limited recyclability of highly cross-linked epoxy matrices pose significant challenges to their sustainable development. Herein, we present an approach combining dynamic ester bonds with semi-interpenetrating polymer networks (SIPNs) to overcome these challenges. This strategy leverages the crosslinked epoxy network to resist deformation, while hydrogen bonds and entangled SIPNs to facilitate energy dissipation, enhancing both strength and toughness. The resultant epoxy matrix exhibits superior tensile strength of 123 MPa and record-breaking impact strength of 52.3 kJ m^-2, effectively overcoming the long-standing trade-off between strength and toughness in thermosets. This balanced performance renders it a promising matrix for high-performance EP-CFRCs, which display a tensile strength of 718 MPa and a bending deflection of 0.59 mm. Moreover, the embedded tertiary amines accelerate transesterification reactions, enabling closed-loop recycling of EP-CFRCs in water. The recycled carbon fibers and the degraded matrix can be reused in new composites and adhesives. This work presents a simple yet effective strategy for designing epoxy resin-based composites that overcome the limitations of traditional matrices and support the development of recyclable advanced materials for diverse industrial applications.