Recyclable Flame-Retardant Thermosets and Their Fiber-Reinforced Composites

Thermosetting composites such as carbon fiber-reinforced epoxy resins are vital for various industries but face sustainability challenges due to their permanent cross-linking nature. Recent advances in dynamic covalent chemistry offer promise for reprocessing, welding, and repairing under mild conditions, yet closed-loop recycling remains elusive. Achieving high flame retardancy introduces further complexities, as traditional treatments hinder recyclability and raise environmental concerns. From this perspective, innovative thermosets incorporating dynamic chemical bonds show potential for reconciling flame retardancy with recyclability. Through clever molecular design, a variety of functional groups have been introduced into dynamic covalent thermosets in different ways. These diverse functional groups not only impart flame retardancy to the target resins and their composites, but also participate directly or indirectly in dynamic covalent exchange reactions. However, challenges persist in balancing dynamic exchange reactions with cured material properties. Despite these challenges, research on recyclable-yet-flame-retardant composites continues to evolve, aiming for comprehensive performances comparable to those of traditional ones. Addressing these challenges requires a multidisciplinary approach that considers material design, performance optimization, and regulatory compliance. Nevertheless, these efforts hold promise in advancing the field toward more environmentally friendly and safer composite materials.