THERMAL AND THERMOOXIDATIVE DEGRADATION OF POLYSTYRENE IN THE PRESENCE OF AMMONIUM-SULFATE

Ammonium sulfate was compounded into polystyrene (PS) to modify therma l degradation of PS. At elevated temperatures, ammonium sulfate decomp oses into ammonia, sulfuric acid and further into sulfur trioxide and water. The aim of the study was to investigate how these acidic and ox idizing compounds affect the thermal and thermo-oxidative degradation behaviour of polystyrene. Thermal degradation was studied by thermochr omatography (ThGC). In addition, isothermal pyrolysis at 340 degrees C was carried out and the dissolved parts of the residues were analyzed by size exclusion chromatography (SEC). The random chain scission ind ex S-r (based on the components of evolving gases), the chain scission number S-x (based on the number-average molar mass), the oxygen effec t K, and the synergistic effect Z were used to describe thermal and th ermo-oxidative degradation processes. The increases of S-r and S-x wit h the increase of ammonium sulfate imply that thermal degradation of P S is modified. The synergistic effect Z indicated that, at low additio n levels, ammonium sulfate synergistically promotes thermo-oxidative d egradation with oxygen. At high addition levels, it promotes thermo-ox idative degradation with oxygen.