Engineering amine-modified ammonium polyphosphate for enhancing flame retardancy and smoke suppression of vinyl ester resin

Vinyl ester resin (VER), as a common thermosetting resin, has been widely used in many engineering fields. However, VER suffers from intrinsic flammability, and it can’t meet the increasingly stringent fire safety requirements. Ammonium polyphosphate (APP) is an environmentally friendly flame retardant, but it needs a high loading level when applied in VER. In this study, the trinity flame retardant (DO) was synthesized through cation exchange reactions between APP and ethylenediamine (EDA) and ethanolamine (EOA). The flame-retardant properties/mechanism and thermal stability of DO/VER composites were investigated in detail. Our results demonstrated that the modification of EDA and EOA allowed DO to achieve better carbonization ability and higher flame-retardant efficiency than APP. For instance, when the molar ratio of EDA and EOA was 3:1, the resultant 26 %DO 3–1 /VER composite (DO 3–1 content: 26 wt%) achieved a limiting oxygen index (LOI) of 26.5 % and a vertical burning (UL-94) V-0 rating. Under the same flame retardant content, 26 % APP/VER composite only showed a LOI of 22.5 % and a UL-94 V-2 rating. Additionally, 26 %DO 3–1 /VER exhibited 74.5 %, 61.5 % and 44.2 % decreases in peak heat release rate (PHRR), peak smoke production rate (PSPR) and total heat release (THR) in comparison to VER. Obviously, DO showed superior flame retardancy and smoke suppression due to the reinforcement effects of EDA and EOA on condensed/gas-phase flame retardancy. This work proposes a facile method for the creation of highly effective APP-based flame retardants by cation exchange, which can be applied to flame-retardant and smoke-suppressive VER. • Highly-efficiency, amine-modified, APP-based flame retardant (DO) was synthesized. • 26 wt% DO endowed VER with an LOI of 26.5 % and a UL-94 V-0 rating. • Adding 26 wt% DO reduced the PHRR and PSPR of VER by 74.5 % and 61.5 %.