Rien Repriels, Campine, presented work to compare ATO (antimony trioxide) as a synergist for halogenated FRs with alternative synergists. ATO does not pose a cancer risk by inhalation if formulated/delivered in a non-respirable form/system, but on the other hand customers want fine product for optimal dispersion.
This can be addressed by supplying granules, wetting or the use of dust-free bags. Alternative synergists (borates, organic additives, stagnates, silicones) were tested in PVC, polyethylene with brominated FR, polyamides with brominated FR, but did not match the fire performance of Campine’s “MT” ATO product. However, these other synergists could be combined with ATO, to obtain in addition to the excellent flame retardant properties of antimony trioxide, reduced smoke emissions or create intumescent layers.