Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE Inspired by mussel adhesive proteins, this study utilized the coordination effect of metal ions to coat ammonium polyphosphate (APP) with dopamine (DA), thereby preparing a series of microencapsulated flame retardants (denoted as M-DA@APP), which were then incorporated into epoxy resin (EP). Among them, the Fe-DA@APP/EP composite exhibited excellent flame retardancy. M-DA@APP significantly reduced the heat release rate, total heat release, and smoke production of the material. This outcome is mainly attributed to the formation of a dense and highly graphitized char layer catalyzed by the metal ions, which effectively insulates heat and oxygen transfer.


ABSTRACT
In this study, inspired by the adhesive proteins of mussels, a series of microencapsulated flame retardants M-DA@APP were prepared by coating ammonium polyphosphate (APP) with dopamine (DA) via coordination with metal ions, and then incorporated into epoxy resin (EP). The effects of these modifiers on the flame retardancy and mechanical properties of EP composites were systematically investigated. The results show that APP modified with Fe3+ or Ni2+ coordination exhibited excellent flame-retardant performance in EP. Specifically, the Fe-DA@APP/EP composite achieved a limiting oxygen index (LOI) of 30.1% and passed the UL-94V-0 rating. Cone calorimetry tests revealed that M-DA@APP significantly reduced the heat release rate, total heat release, and smoke production. The flame-retardant mechanism is mainly attributed to the metal-ion-catalyzed formation of a dense, highly graphitized char layer, which effectively insulates heat and oxygen. Moreover, owing to the improved interfacial compatibility between APP and the EP matrix enabled by the M-DA coating, the impact strength, tensile strength, and elongation at break of the composites were notably enhanced, overcoming the negative effect of conventional APP on mechanical performance. This work offers a promising strategy for developing efficient, environmentally friendly epoxy resin composites with superior flame retardancy and mechanical properties.