Synergistic effect of ferric chloride and silicon mixtures on the thermal stabilization enhancement of ABS

A previous study from this laboratory has shown that Lewis acid-type transition metal chlorides (NiCl2, CoCl2, ZnCl2, and FeCl3) are effective char forming catalysts for ABS terpolymer in an inert atmosphere [Jang J, Kim JH, Bae JY. Polym Degrad Stab 2005;88(2):324.]. However, transition metal chloride catalysed char formation (and flame-retardance enhancement) of ABS in air was unsuccessful due to the oxidative degradation of the char at a higher temperature. In order to overcome these undesirable phenomena, we incorporated silicon with transition metal chlorides as co-catalyst and a series of ABS/transition metal chloride/silicon compounds were made from them and their flame retardancy was evaluated by measuring the limiting oxygen index (LOI) values. Our results showed that among various transition metal chloride/silicon catalyst systems the incorporated mixture of ferric chloride and silicon is very effective in enhancing the thermal stabilization of ABS and LOI value as high as 33 is obtained. The reason for this synergistic effect by ferric chloride and silicon was postulated to come from the interaction between ferric chloride and silicon at elevated temperatures, probably generating silicon tetrachloride and hydrogen chloride.