Thermal decomposition investigation of ABS containing Lewis-acid type metal salts

The thermal decomposition of acrylonitrile-butadiene-styrene (ABS) copolymer in the presence of different Lewis-acid type metal salts is addressed in this paper. Indeed, the thermal decomposition is directly affecting the behavior of the polymer once exposed to a flame. ABS is a very important impact resistant polymer for applications in automotive and electrical appliances, where flame retardancy is a must. The traditional and still most common flame retardants used in ABS are halogenated organic additives, which are anyway posing health and safety concerns and are therefore being progressively restricted. A possible alternative option to improve flame retardancy is to promote the char formation of ABS during its combustion, which requires additives able to effectively char the polymer during the early stage of its thermal decomposition. Tin- and zinc-based Lewis-acid salts were demonstrated as possible charring additives in this paper, showing different degrees of effectiveness in ABS charring during thermal decomposition. Furthermore, insights in the thermal decomposition mechanisms were obtained by the infrared analysis of evolved gases during decomposition, both on heating and in isothermal conditions.