Solvent exchange strategy for the construction of novel smoke-suppressing, mechanically robust flame-retardant epoxy resins

Achieving a balance between flame retardancy, smoke suppression and mechanical properties of epoxy resin (EP) remains challenging in industry and academia. Herein, a novel polyphosphazene microsphere (PZS) was synthesised by precipitation polymerization. Further, BPF@PZS with core–shell structure was prepared by solvent exchange strategy for flame retardant EP. The precipitation polymerization confers PZS enriched with modifiable amino groups and natural P and N synergistic flame retardation. The solvent exchange provides BPF@PZS with good dispersion properties and char formation. The addition of only 5 wt% of BPF@PZS reduces the total heat release (THR) and total smoke production (TSP) during combustion by 40.6 % and 56.5 %, respectively, and results in a high LOI of 28.9%. Meanwhile, EP-BPF@PZS exhibits excellent mechanical properties due to the homogeneous spreading of BPF@PZS. This work broadens the application scenarios for the development of multifunctional and high-performance epoxy resins.