Abstract: A new flame retardant, trimethyl silicate-1-thiophospha-2,6,7-trioxabicyclo［2.2.2］ octyl-4-methyl ester (TMSSPE), was synthesized by the reaction of trimethyl chlorosilane(TMCS) with 1-thiophospha-4-hydroxymethyl-2,6,7-trioxabicyclo［2.2.2］ octane (SPEPA). The effects of solvent, reaction temperature, reaction time and molar ratio on the yield were investigated extensively. The structure and flame retardant properties of the obtained product were characterized by means of Fourier-transform infrared spectroscopy, 1H-nuclear magnetic resonance spectroscopy, thermogravimetric analysis and limiting oxygen index. The results indicated that the yield reached 93.2 % when the optimal synthetic conditions were set to a n（SPEPA：TMCS）=1.2, a reaction temperature of 45 ℃ and a reaction period of 9 h as well as using dioxane as a solvent. The reactant flame retardant achieved a good thermal stability and the char yield was 25 % at 700 ℃, the limiting oxygen index of PP was 27 % at a content of 20 wt % when being applied for polypropylene (PP). In addition, when this flame retardant was complexed with melamine pyrophosphate or melamine cyanurate, it can generate a high synergistic flame-retardant efficiency for PP.

Key words: trimethyl chlorosilane, silicone flame retardant, cage flame retardant, charring