Phytic acid doped polyaniline-coupled g-C3N4 nanosheets for synergizing with APP promoting fire safety and waterproof performance of epoxy composites

In this study, polyaniline-coupled graphitic carbon nitride (g-C3N4) doped with phytic acid (CP@PA ) hybrids are prepared by an in-situ chemical oxidative method. The CP@PA and APP (Ammonium Polyphosphate) are added into epoxy resin (EP) for EP composites. The characteristic test results show that CP@PA can react with epoxy resin (EP) to promote the curing of EP. And CP@PA disperses in EP uniformly. The cone calorimetry test (CCT) results show that the pHRR, THR, and TSP of EP-8A4CP@PA (the EP sample with 8.0 wt% APP and 4.0 wt% CP@PA ) reduce 85%, 76.8%, and 78.9%, respectively than EP-0 (pure EP), which are lower than any other samples. The results of the back temperature test show that EP-8A4CP@PA has better thermal insulation and flame-retardant properties than EP-12APP (the EP sample with 12.0 wt% APP). Moreover, CP@PA promotes the waterproof properties of EP with APP composites by synergizing with APP to form a labyrinth effect. After a comprehensive analysis, the fire protection mechanisms of EP-8A4CP@PA are proposed as follows. CP@PA promote EP charring and make more aromatic structure remain in the char. And CP@PA has a synergistic effect with APP to promote EP to form porous intumescent char layer with a higher graphitic degree, which protects the composites from the flame. As a result, the combination of CP@PA and APP in EP achieved a lower addition of flame retardant and better waterproof and fire safety performance, which provides a specific experimental and theoretical basis for the further application of CP@PA in epoxy resin. (C) 2022 Published by Elsevier Ltd.