A careful comparison on the synergistic flame retardant effect of sodium dodecyl sulfate modified layered double hydroxide(SDS-LDH) and hexadecyl trimethyl ammonium bromide modified montmorillonite(CTAB-MMT) with ammonium polyphosphate(APP) on poly(butyl acrylate-vinyl acetate)(P(BA-VAc)) has been done based on the results of limiting oxygen index(LOI) and vertical burning test(UL-94).P(BA-VAc)/APP/SDS-LDH and P(BA-VAc)/APP/CTAB-MMT owned the highest LOI value at 30.5 and 30.1

respectively

when APP content is 14.5% and layered particle content is 0.5% in flame retardant composites.Thermal degradation behaviors of flame retardant composites were investigated through thermogravimetric analysis(TGA).The amount of char residues of P(BA-VAc)/14.5%APP/0.5%SDS-LDH at 700 ℃ was 2.7 percentage points higher than that of P(BA-VAc)/14.5%APP/0.5%CTAB-MMT.Morphologies and microstructures of residues generated during LOI test were investigated by scanning electron microscopy(SEM).P(BA-VAc)/14.5%APP/0.5%SDS-LDH and P(BA-VAc)/14.5%APP/0.5%CTAB-MMT had more continuous and compact char layer than that of P(BA-VAc)/15%APP.Fourier transform infrared spectroscopy(FTIR)

and X-ray photoelectron spectroscopy(XPS) were used to determine the composition of the residues formed by thermal oxidation at 500 ℃.SDS-LDH and CTAB-MMT could promote more esterification and dehydration during the combustion of flame retardant composites.SDS-LDH had a little better synergistic flame retardant effect with APP on char formation.