Ceramic sintering-inspired fabrication of P/N/B-based flame retardant toward high-efficiency fire safety and smoke suppression in ethylene-vinyl acetate

The high flammability and severe dripping behavior of ethylene-vinyl acetate (EVA) limit its widespread application. It remains a persistent challenge to enhance the flame retardancy and smoke suppression performance of EVA composites while maintaining their tensile properties. In this study, a microencapsulated P/N/B-based flame retardant, referred to as MBPAPP, was synthesized via a one-pot method. The flame retardant consists of a melamine-boric acid composite (MA-BA, shell) and piperazine pyrophosphate (PAPP, core). At a loading of 20 wt% MBPAPP, EVA/MBPAPP composite achieves a UL-94 V-0 rating without dripping. In the cone calorimetry test, compared with EVA/PAPP, EVA/MBPAPP exhibits reductions in the peak heat release rate (50.5 %), total heat release (16.9 %), total smoke production (17.1 %), and the peak of CO content (52.5 %). This is attributed to the fact that EVA/MBPAPP forms a boron-containing char layer composed of B-O and B-N structures, contributing to the enhancement of compactness and thermal stability. Moreover, compared with PAPP, microencapsulation enhances the compatibility between modified MBPAPP and EVA, mitigating the deterioration of tensile properties in the composite.