Today, flame retardants are mostly used as systems consisting of several components. The benefits of synergistic effects are particularly taken into account. Synergism means that the overall flame retardancy effect is higher than the sum of the single components effects.
A classical example is the synergy of antimony trioxide (ATO) with brominated or chlorinated compounds. ATO alone has no flame retardancy effect; with Br/Cl compounds, however, it is higher than the sum of the single effects.
Many synergistic systems based on phosphorous and nitrogen, metal hydroxides and salts have been developed in recent years. Examples are the synergy between metal phosphinates and melamine polyphosphate, as well as aluminum oxide hydrate (boehmite) or melamine polymetal phosphates.
