Effects of Lewis acid-type transition metal chloride additives on the thermal degradation of ABS

The thermal degradation of ABS in the presence of Lewis acid-type transition metal chloride additives has been studied by thermogravimetric analysis. The reaction of transition metal chlorides (NiCl2, CoCl2, ZnCl2 and FeCl3) and ABS has been found to occur during the thermal degradation of ABS. In an inert atmosphere, char formation is observed, and some 10-30% of the reaction product is non-volatile at 600 °C. From model studies, it was found that the interaction of transition metal chloride and the acrylonitrile moieties of ABS at elevated temperatures leads to crosslinking of the polymer. The resulting enhancement of char formation in an inert atmosphere has been explained as a catalytic crosslinking effect of transition metal chloride compounds via a macroradical coupling mechanism. Although this crosslinking does not increase the threshold temperature for decomposition of ABS, it decreases the formation of flammable small molecules. On the other hand, transition metal chloride catalysed char formation of ABS in air was unsuccessful due to the oxidative degradation of the char at a higher temperature.