A DOPO-anchored benzothiadiazole derivative toward efficiently P/N/S synergistic flame retarding of epoxy thermoset

Flame-retarded epoxy thermosets are highly desirable for electronics-related basic materials in the new-generation information applications. Herein, a DOPO-anchored benzothiadiazole flame retardant, namely DOPO-BTD , is designed and synthesized for P/N/S synergistic flame-retarded epoxy thermosets. DOPO-BTD possesses good thermal stability and excellent compatibility with the epoxy matrix. As reflected by UL 94 test, the DOPO-BTD coated EP passes the V0 rating and achieves a higher LOI value of 34.6% at ultralow P content of 0.39 wt%. The investigation of the DOPO-BTD -triggered P/N/S synergistic flame-retarded effect by thermal images further validated the flame retarded efficacy and dramatic inhibition of the flame. Meanwhile, the incorporation of 4.8 wt% DOPO-BTD into the epoxy matrix, the PHRR, THR, SPR, TSP, and COP are significantly decreased by 37.97%, 27.44%, 25.49%, 19.83%, and 31.70%, respectively. Additionally, the fire growth index (FGI) is sharply dropped 26.06%. Moreover, the TGIR and TGMS results convince the flame-retarded mechanism of DOPO-BTD through the combination of the gas-phase and condensed-phase pathways. The P/N/S synergistic DOPO-BTD can serve as a promising flame retardant for efficiently fabricating the flame-retarded epoxy thermosets, and this study sheds light on the development of multiple elements synergistic flame-retardants for functional polymers with great application potential.