In the present paper, a novel biomass flame retardant based on alginic acid was synthesized through chemical combination with a reactive P–Si compound. Compared with alginates, the modified alginate showed obviously increased thermal stability and water resisting property, as well as better compatibility with epoxy resin, which can satisfy the requirements of a flame-retardant additive in the polymer. The flame-retardant properties were evaluated by vertical burning tests, limiting oxygen index, and microscale combustion calorimetry. Due to the self-charring capacity of alginate combined with the charring catalyst from P and the charring reinforcer from Si, the modified alginate exhibited much better flame retardancy, taking advantage of the formation of a more continuous, denser, and strengthened char layer than either individual alginate or P–Si flame retardant. The corresponding flame-retardant mechanisms were investigated and discussed.

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© 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017134, 45552.