Synergistic Effects of Iron Alginate on Improving the Fire Safety and Mechanical Properties of Epoxy Resin/Ammonium Polyphosphate Composites

Iron alginate is chosen as an eco-friendly synergist to improve the flame retardancy, smoke suppression, and mechanical properties of epoxy resin/ammonium polyphosphate composites (EP/APP). The suitable additive amount of iron alginate further enhances the char-forming ability in the higher-temperature range and flame retardancy of EP/APP. EP/APP9.0-iron alginate1.0 retains a char residue of 33.3% at 700 °C and obtains a limiting oxygen index value of 28.4% and vertical burning test (UL-94) V-0 rating, while EP/APP10 has no UL-94 rating. The burning behaviors of EP/APP9.0-iron alginate1.0 are also suppressed; and the total smoke production value is much lower than that of EP/APP10. EP/APP9.0-iron alginate1.0 releases less smoke and flammable fragments. The suitable additive amount of iron alginate boosts the mechanical properties of EP/APP, while APP destroys the mechanical properties of EP. Therefore, the addition of suitable amount of iron alginates can further reduce the fire hazard, and improve the mechanical properties of EP/APP composites.