Abstract: Aluminum hypophosphite (AHP) and Zinc hydroxystannat (ZHS) were synthesized through homogeneous precipitation method. And then ZHS was calcined in a muffle furnace at 300 ℃ for 3 h forming amorphous zinc stannate (ZS). AHP and ZS were used as a flame retardant for poly (1,4butylene terephthalate) (PBT). When the content of ZS was 1.4 %, limiting oxygen index increased from 21.8 % for neat PBT to 24.1 %，and UL 94 rating reached V-0. In addition, the heat release rate was decreased to 538.57 W/g from 561.40 W/g for neat PBT.

Key words: aluminum hypophosphite;zinc stannate;flame retardant;poly (1;4-butylene terephthalate), synergistic