Design of degradable, intrinsically flame-retardant and high-performance tung-oil-based epoxy vitrimers†

The performance of carbon fiber-reinforced composites (CFRCs) is mainly influenced by the resin matrix. In this study, eleostearic acid was utilized as the raw material, with DOPO serving as the flame-retardant functional group, and dynamic ester bonds were introduced to construct tung oil-based flame-retardant epoxy vitrimers (DGEBA-MSPDGE), which were subsequently applied in the preparation of CFRCs. This approach was aimed to address two major challenges of CFRCs: flammability and recyclability. With DGEBA-MNA cured with commercial methyl nadic anhydride (MNA) as a control, DGEBA-MSPDGE-1 exhibited excellent mechanical properties, and achieved a tensile strength of 81.4 MPa and an elongation at break of 3.83%, which were both superior to those of DGEBA-MNA (76.1 MPa and 2.86%, respectively). DGEBA-MSPDGE attained a limiting oxygen index of 36.4% and a UL-94 V-0 rating in a vertical burning test, and demonstrated blow-off effects during evaluation. The peak heat release rate and total heat release for DGEBA-MSPDGE-1 compared to those of DGEBA-MNA were reduced by 40% and 46%, respectively, which indicate excellent flame retardancy properties. It displayed excellent chemical degradability by completely degrading within five hours under mild conditions. Notably, the recovered carbon fibers (CFs) retained their original chemical structure, mechanical properties, and surface morphology, which facilitated non-destructive recycling of CFs. Therefore, this research provides a viable strategy for fabricating high-performance, fire-safe and recyclable CFRCs.