Abstract

Antimony, boron, aluminum, tin, zinc, and molybdenum are inorganic flame retardants or flame-retardant synergists used to improve the flame retardancy obtained from incorporating halogens in plastics. Combinations of the synergists and the halogens are used at lower concentrations than the halogens alone, resulting in more flame-resistant plastics that have better physical properties. Antimony oxide is the most effective flame-retarder synergist; alumina trihydrate is the most widely used. Synergists used in combination often enhance one another. The mechanisms of inorganic synergist-halogen flame-retarder systems are discussed for both the condensed and flame phases. A series of typical formulations for various polymer materials is given.