Influence of brominated flame retardant thermal decomposition products on HALS

Brominated flame retardants may undergo thermal decomposition at temperatures lower than those of polymer combustion. Decabromodiphenyl ether, which was the main subject of this study, exhibits a threshold decomposition temperature that is close to polypropylene processing temperatures. In the presence of hydrocarbon polymer the loss of bromine leads to the formation of lower brominated by-products and hydrobromic acid. The latter attacks stabiliser package components, HALS in particular. The aminium hydrobromide salt thus formed is well known to be inefficient as a stabiliser. Moreover, it has been found in this work that it is less thermally stable than the parent amine. In the case of polypropylene it has been demonstrated that excessive processing temperature of polymer containing polybrominated aromatic flame retardant and HALS results in an irreversible loss of the light stabiliser from the very beginning of material service life.