Synergistic action of fluorine-containing additives in bromine antimony fire retardant ABS

Small amounts of poly(tetrafluoroethylene) (PTFE), added to several polymer s fire retarded with Sb/Br synergistic systems can significantly improve th eir fire retardance. The chemical interaction between PTFE and Sb2O3 leads to evolution of volatile Sb-containing species which however are nor respon sible for the whole mechanism of fire retardance because the improvement re quires the contemporary presence of the polymer, the Sb/Br system and PTFE. The combustion behaviour of fire retarded (FR) Acrylonitrile-Styrene-Butad iene (ABS) formulation containing SbF3 is investigated, which is likely to be formed in high temperature reaction between PTFE and Sb2O3 Thr parallel combustion behaviour of PTFE and SbF3-containing ABS FR formulations confir ms that SbF3 might be one of the truly active fire retardant agents in the system. In its presence combustion is slowed down but the extinguishment of the flame is delayed. However, as soon as combustion develops, the additio nal effect of the fluorine containing compound is no longer significant and the fire retardance is restricted to that of the synergic Br/Sb system. It is proposed that SbF3 plays some role in increasing the molecular weight o f the ABS chains, for example, catalysing the polymerisation of polybutadie ne double bonds with increase of thermal resistance of the: material and re duced flame feeding rate. (C) 1999 Elsevier Science Ltd. All rights reserve d.