Strong, Recyclable, Bio-Based Vitrimers by Tailored Rigid-Flexible Structures for Advanced Carbon Fiber-Reinforced Polymers

Carbon fiber-reinforced polymers (CFRPs) are typically composed of carbon fibers (CFs) and epoxy (EP) resins, which have been widely utilized in diverse industries. However, the irreversible cross-linked network of conventional EP resins and their dependence on petroleum-based resources present serious challenges to the sustainable development of CFRPs. Herein,a bio-based, high-performance and recyclable EP (F9T1) is reported by integrating rigid and flexible networks using two fully bio-based epoxy monomers: i) DGEFA, featuring a rigid conjugated structure, and ii) DGETA, containing a flexible fatty acid backbone with dynamic disulfide groups. Owing to the presence of abundant aromatic structures and disulfide groups, F9T1 features exceptional char-forming ability, flame retardancy and smoke suppression. Compared with commercial epoxy system (DGEBA), F9T1 shows superior mechanical performance due to its rigid-flexible network, with enhancements of 56.1%, 19.2% and 28.9% in tensile strength, elongation at break and flexural strength, respectively. The intrinsic degradability of F9T1 enables the fabrication of recyclable CFRPs with improved flame-retardant and mechanical properties, in which the CFs can be completely reclaimed. Thus, this work establishes a promising design strategy for the creation of next-generation sustainable thermosetting resins and CFRPs by constructing bio-based rigid-flexible dynamic covalent networks.