Fire-resistant and high-performance epoxy vitrimers for fully recyclable carbon fiber-reinforced composites

For recyclable carbon fiber-reinforced composites (CFRC), epoxy vitrimers are frequently utilized as matrix. However, there are a number of limitations on these vitrimer matrices, including a relatively low glass transition temperature (T-g), insufficient strength, and flammability. Creating epoxy vitrimers with improved strength, high T-g, and fire-safe properties are the aim of this work. For usage in recyclable and fire-safe CFRC, the vitrimer was created specifically. By curing bisphenol-A diglycidyl ether with a vanillin-derived imine hardener, and incorporating 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-HQ) for reactive flame-retardant, we achieved high-performance epoxy vitrimers with impressive tensile strength (>80 MPa), T-g (>= 135 degrees C), and flame retardancy as well as excellent reprocessability. The vitrimer, EVHQ2.0 (22 wt% DOPO-HQ), showed excellent flame retardancy (LOI: 32.5%, V-0 rating in UL-94). Using EVHQ2.0 as the matrix, we obtained CFRC, with remarkable mechanical performance (flexural strength: 480.4 MPa, flexural modulus: 31.7 GPa). Moreover, the CFRC demonstrated a high level of fire safety, achieving a V-0 rating and possessing a LOI value of 35.5%. Additionally, we also realized non-destructive recovery for valuable carbon cloth through chemically decomposing the vitrimer network using additional diamines. What's particularly noteworthy is that by reassembling the deteriorated vitrimer with reclaimed carbon fiber, the composite can be completely recycled. A carbon fiber reinforced composite with mechanical characteristics similar to the primary composite is created by this method. This research breakthrough holds significant implications for the development of recyclable composites with fire-resistant properties and improved mechanical performance.