The most important flame retardants, which are also used as fillers, are aluminum trihydrate (ATH) and magnesium hydroxide (MDH). In addition, antimony trioxide (ATO) is used in large quantities as a synergist with halogenated flame retardants and PVC. Aluminum oxide hydrate (AlOOH or Boehmite) also acts as a synergist in conjunction with metal phosphinates.

Aluminum hydroxide or aluminum trihydrate (ATH) already decomposes at around 200 °C.

Therefore, it only can be used with plastics processed at lower temperatures such as PVC, polyethylene, ethylene/vinyl acetate-copolymers and thermosets.

Aluminum oxide hydrate (AlooH) or Boehmite decomposes at 320 °C. It can therefore be used in engineering thermoplastics and is synergistic with metal phosphinates. It iss also used in printed circuit boards.


Magnesium hydroxide (MDH) decomposes at around 300 °C.

Its main applications are polypropylene, polyamides and wire & cable.

Zinc borate may partly substitute antimony trioxide in thermoplastics, inhibits afterglow and acts as a smoke suppressant. 4ZnO . B2O3 .H2O, which decomposes at 415 °C, is suitable for engineering plastics.

Zinc hydroxystannate is used as a smoke suppressant for PVC, unsaturated polyesters and elastomers.