Unraveling a path for multi-cycle recycling of tailored fiber-reinforced vitrimer composites

Manufacturing transformation toward a net-zero carbon society demands polymeric composite materials to be reprocessable in circularity in an energy-efficient and stable manner. Recent advancements in vitrimers have bestowed crosslinked polymers like epoxies with reprocessability, opening a path for the circular manufacturing of thermosets. However, (re)processing of mechanically robust vitrimers such as epoxy vitrimers typically requires high temperatures and long processing times, which cause degradation and compromise efficient recyclability. Here, we report a simple design of dynamic polyurea/epoxy (DPE) vitrimers and their carbon-fiber-reinforced polymers (CFRPs) with exchangeable disulfide crosslinks, which overcome such intrinsic limitations. Compared with conventional epoxy vitrimers, the DPE vitrimer exhibits 6 times faster bond rearrangement and ∼40°C lower reprocessing temperature, which enables full recovery of the mechanical strength throughout 6 reprocessing cycles, while the conventional vitrimer lost ∼63% of strength. Moreover, the CFRPs prepared with the DPE vitrimers exhibit facile multi-cycle processability and repairability by thermoformation.