High glass transition catalyst-free fire-retardant polybenzoxazine vitrimer through solventless one-pot method

A high-temperature polybenzoxazine vitrimer has been synthesised by a solventless one-pot method involving the Mannich condensation of a phenolic disulphide, paraformaldehyde and aniline. The polybenzoxazine has a glass transition temperature of 155°C and exhibits thermosetting behaviour below the glass transition temperature. Dynamic bond exchange enabled by disulphide metathesis associated with a topological freezing temperature of 78°C results in healing over the glass transition temperature. The system is reprocessable at 190°C, has a glassy modulus of 3.6 GPa, and a limiting oxygen index (LOI) of 40.5%. The combination of thermosetting character, ease of synthesis, good processability, fire retardancy and reprocessability of this polybenzoxazine vitrimer system make it an attractive candidate material solution as a matrix for recyclable and self-repairable aerospace thermosetting continuous fibre composites.