Thermal Decomposition of Styrene Methyl Methacrylate and Expanded Polystyrene via Ball-Mill-Assisted Pyrolysis

Virgin styrene methyl methacrylate (SMMA) and expanded polystyrene (EPS) were pyrolyzed in a ball-mill-type reactor developed by modifying a conventional rotary kiln-type system. The pyrolysis experiments were conducted within a temperature range of 500–700 °C and 450–650 °C for virgin SMMA and EPS, respectively. The optimal pyrolysis temperatures for virgin SMMA and EPS were 650 °C and 600 °C, respectively, with corresponding liquid product yields of 87.3% and 88.2%. The gas chromatography–mass spectrometry of the recovered liquid products showed that the major components were styrene and methyl methacrylate for virgin SMMA and styrene for EPS. Comparative pyrolysis experiments of the rotary kiln-type and ball-mill-type reactors showed that the ball-mill-type reactor achieved significantly higher liquid product recovery rates than the conventional rotary kiln-type reactor.