A novel polyphenol-metal chelation-based structure enabling epoxy with outstanding flame retardancy, toughening effect, smoke suppression performance and recyclability

As a typical thermosetting polymer, epoxy resin (EP) is severely limited in expanding its applications in high-end fields due to its inherent brittleness and flammability. In this study, a novel flame retardant, namely PPCD-Fe, was designed and synthesized to simultaneously enhance the flame-retardant efficiency and mechanical properties of EP. The results demonstrated that with the incorporation of merely 2 wt% PPCD-Fe, the composite passed the UL-94  V -0 rating, and its limiting oxygen index (LOI) was significantly increased to 33.1%. Furthermore, compared with pure EP, the peak heat release rate (PHRR), smoke production rate (SPR), and carbon monoxide yield (COP) of the composite were reduced by 52.9%, 38.7%, and 56.7% respectively, indicating a substantial improvement in flame retardance and smoke suppression performance. Meanwhile, the impact strength, tensile strength, and flexural strength of the composite increased by 256.3%, 98.6%, and 44.5% respectively comparing to that of EP. Moreover, the degradation products of flame-retardant epoxy resin (FREP) could be compounded with polyvinyl alcohol (PVA) to prepare thermally insulating and flame-retarding aerogels without complex separation and purification processes. When the addition amount of degradation products was 5 wt%, the PHRR of the aerogel was reduced by 35.9% compared with pure PVA aerogel, demonstrating excellent secondary application value.