In order to improve the flame retardant efficiency, ammonium polyphosphate (marked as A), microcrystal cellulose (marked as C) and melamine cyanourate (marked as M) were selected as the basic components to prepare microencapsulated intumescent flame retardants, noted as M(A&C), via combination of ball-milling and in-situ synthesis techniques. M(A&C) was subsequently incorporated into polylactic acid (PLA) via melt blending method to get the PLA/M(A&C) samples. The structure of MA&C, thermal properties, flame retardancyand residual carbon morphology of flame retardantsamples were characterized with the help of thermogravimetric, Fourier transform infrared, X-ray photoelectron spectroscopy and scanning electron microscope. The results show that PLA/M(A&C) demonstrates better flame retardant ability than PLA/(M+A+C), with the same loadings of flame retardant (3%, 5% and 10% mass fraction, respectively). The limit oxygen index of the former samples was 27%, 29%, and 31.5%, respectively, which is obviously higher than those of the latter samples (24%, 25%, anf 28.5%, respectively). The overall flame retardancy of PLA/M(A&C)-10 is found excellent, achieving UL-94 V-0 grade. The peak heat release rate, total heat release and char residue show obvious flame retardancy properties, with the values of 313 kW/m2, 54 MJ/m2, and 16.1%, respectively.
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