Abstract: A novel flame retardant composed of hexachlorocyclotriphosphazene (HCCP) modified by silicon and boron moieties (HCCP-Si-B) was used as flame retardant for PET. The chemical structure of HCCP-Si-B was characterized by FTIR and NMR. The flame retardancy of PET was investigated by limited oxygen index and vertical burning test. SEM was used to investigate the morphology of the char residue. It showed that HCCP-Si-B had excellent flame retardant property,the sample achieved UL 94 V-0 rating and the limited oxygen index value more than 30% while the content of HCCP-Si-B was only 1%. The coat-like char formed in the outer char surface of composites and many micro porous cells in inner surface. Such a structure provided a barrier for the PET material during burning.

Key words: hexaphenoxycyclotriphosphaze, modification, poly (ethylene terephthalate), flame retardancy