Facile fabrication of intrinsically fire-safety epoxy resin cured with phosphorus-containing transition metal complexes for flame retardation, smoke suppression, and latent curing behavior

Concerning the application of fire-safety epoxy resin (EP) in electrical and electronic devices, a question may inevitably arise: how can fire hazards be reduced without compromising comprehensive properties? Herein, this work presented a solution to fabricate intrinsic fire-safety EPs with attractive properties by introducing phosphorus-containing transition metal complexes as multifunctional curing agents. Cured with 15 wt% DPPSSZn, the EP thermoset exhibited superb fire safety performance, and the testing samples achieved a V-0 rating in the UL-94 vertical burning test and possessed an upgraded LOI value of 36.5%. Additionally, the peak heat release rate (pHRR) and the total smoke production (TSP) showed 71.4% and 74.3% decreases, respectively. Similar results were found in the system by replacing Zn with Co ions. Furthermore, the prepared EP possessed latent curing behaviors within 90 days with rather low complex viscosity. Lower dielectric constant and dielectric loss factors were obtained owing to the uniform dispersion and the relatively low polarized networks enabled by the reactive metal complexes. Hence, this work proposed a feasible and simple strategy for developing intrinsic fire-safety thermosets with desirable comprehensive properties.