Flame-retarding polypropylene with tin compounds

Abstract

Studies have been carried out to evaluate the flame-retardant properties of zinc stannate (ZnSnO₃) and zinc hydroxystannate (ZnSn(OH)₆), relative to those of antimony trioxide in polypropylene. It was found that zinc stannate and zinc hydroxystannate exhibited the marked flame retardant synergism with decabromodiphenyl oxide (DBDPO), whereas the effectiveness of tin compounds as flame retardants depended on the incorporation level of DBDPO compound. Furthermore, zinc hydroxystannate showed similar flame retardancy as antimony trioxide, whereas zinc stannate showed the less flame retardancy in brominated polypropylene. In the observation of mechanical properties, tin additives had small effect on mechanical properties of brominated polypropylene. Thermoanalytical and related mechanistic experiments of polypropylene suggested that the flame-retardant actions of the tin additives involves both the condensed and vapor phases. Tin compounds appeared to act in the condensed phase by a char-promotion mechanism, and this leads to significant decrease in the amount of smoke and toxic gases evolved during polymer combustion.