Tertiary Resource Recovery from Waste Polymers via Pyrolysis:  Neat and Binary Mixture Reactions of Polypropylene and Polystyrene

Batch pyrolysis of polypropylene, polystyrene, and their binary mixture was carried out at temperatures of 350 and 420 °C. Two different loadings were also studied for neat polypropylene and polystyrene to assess the impact of total pressure, which was also a function of reaction time and temperature. For neat polypropylene pyrolysis, total conversion was an order of magnitude higher at 420 °C than at 350 °C. For neat polystyrene pyrolysis, conversion reached approximately 75% at 350 °C, whereas at 420 °C, the conversion reached a maximum of approximately 90% after 10 min of reaction and decreased to approximately 70% after 180 min. For binary mixture pyrolysis, the overall conversion was higher than the average of the conversions for the two neat cases. The conversion of polystyrene remained the same, but significant enhancement of the polypropylene conversion was observed. These results suggest that the more facile degradation of polystyrene helped to initiate the less reactive polypropylene.