Synergists such as Zinc borate are supplied for the non-halogenated Fire Retardant systems that are now replacing brominated systems.
Zinc borate is primarily used as a flame retardant and smoke suppressant in plastics, paints, fibres, rubbers and textiles. It can be used in both halogen-based and halogen-free systems. Zinc borate degrades endothermically and releases its water of hydration at temperatures above 290 °C, this cools the flames and reduces the energy to the fire. It promotes the formation of a protective layer, reducing the formation of toxic smoke. Zinc borate acts as a synergist in conjunction with halogenated compounds, thus lower amounts of halogenated flame retardant are required. It has a synergistic effect with antimony trioxide, this effect is enhanced when in the presence of alumina trihydrate. Zinc borate is an afterglow suppressant and improves electrical degradation resistance. Bisley supplies a variety of zinc borates depending on the specifications required.