Abstract: Using sodium stannate and lanthanum nitrate as raw materials and sodium hydroxide solution as pH regulator, spherical like lanthanum stannate (La2Sn2O7) particles were prepared by hydrothermal synthesis method at pH values of 9, 10 and 11. The flame retardancy and tensile strength of poly (vinyl chloride) (PVC) treated with the asprepared three kinds of La2Sn2O7 were studied, and the char residues of neat PVC and flame retardant PVC with the best integrate properties were compared. The result indicated that PVC sample treated with La2Sn2O7 prepared at pH=9 gave the best flame retardant and tensile properties; when the loading level of La2Sn2O7was 5 g/100 g PVC, the limited oxygen index was 30.8 %, and its tensile property was slightly higher than that of neat PVC, which formed a compact char layer with a closed porosity.

Key words: lanthanum stannate, poly（vinyl chloride）, flame retardant, char residue