Facile synthesis of phytic acid and aluminum hydroxide chelate-mediated hybrid complex toward fire safety of ethylene-vinyl acetate copolymer

Abstract A bio-based intumescent flame retardant (denoted as PIMEPA@ATH) was synthesized via metal chelation using water as the media. The PIMEPA@ATH complex aggregations was used to improve the flame retardancy of ethylene-vinyl acetate copolymer (EVA) by synergistic combination of piperazine-melamine phytate complex (denoted as PIMEPA) and aluminum hydroxide (ATH). During combustion, the in-situ growth of crystalline aluminum metaphosphate arising from PIMEPA@ATH helped to cast more compact protective barriers containing metal ions and aromatic rings. The results showed that the EVA sample containing 30 wt% PIMEPA@ATH achieved the UL-94 V0 rating without dripping in the vertical burning test and a reduction of 79% in peak heat release rate and 58% reduced peak smoke production rate in the cone calorimeter test. Moreover, the tensile properties of EVA/PIMEPA@ATH were improved compared with the EVA/PIMEPA control. Better char formation and improved interfacial adhesion were primarily responsible for the enhancements in flame retardancy and mechanical performance. This work demonstrated the flame-retardant mechanism of PIMEPA@ATH, and explored a facile and green “chelate-mediated” strategy for synthesis of bio-based and ATH chelate-mediated intumescent flame retardant.