Abstract: In this study， aluminum hypophosphite（AlHP） flame retardant was synthesized with industrial by-products and sodium hypophosphite through one-step reaction. The structure and thermal behavior of the product were characterized by 1H-NMR，31P-NMR，FTIR，XRF，XRD and TGA. As a flame retardant being used in PBT，the limit oxygen index（LOI） of PBT with 20wt% filler loading improved from 16. 6% to 29. 2%，and the vertical burning test reached UL94 V-0 grade. Moreover，not only the heat release rate（HRR） of PBT decreased obviously with the adding of AlHP，but also the formation of a stable carbon layer had been promoted.

Key words: aluminum hypophosphite, flame retardant, synthesis, PBT