Pyrolysis Kinetics of Expanded Polystyrene and Polystyrene Wastes

The increasing production of non-degradable polymer wastes such as polystyrene (PS) and expandable polystyrene (EPS) is known as one of the most important environmental issues. Pyrolysis is one of the strategic and suitable methods for recycling of non-degradable polymeric wastes to fuels and useful chemicals. Therefore, investigation of pyrolysis kinetic of polystyrene waste, especially for available materials in Iran, is an essential issue for their use in industries. Obtaining the polystyrene pyrolysis kinetic can be used in designing industrial reactors and where it has economic credibility, styrene monomers can be produced in an industrial scale from polystyrene wastes.

Polystyrene (PS) and expandable polystyrene (EPS) samples that are available in Iran were collected, and their TGA analysis was performed in a nitrogen atmosphere in the temperature range of 25 to 600oC, at heating rates of 5, 10, 15, and 20 C/min, and sample mass changes were measured. The activation energy of pyrolysis was estimated by the Coats Redfern (CR), Ozawa Flynn Wall (OFW), Kissinger Akahira Sunose (KAS), Augis Bennetis (AB) and Vyazovkin methods.

The Vyazovkin model can predict the experimental data better than the other models, and therefore this model was used to estimate the activation energy. The activation energies of PS and EPS were calculated in the range of 158-201 kJ/mole and 182-195 kJ/mole, respectively. Furthermore, the pre-exponential factors of PS and EPS were estimated by Vyazovkin approach as 3.08×1012 and 1.05×1015, respectively. The results of kinetic analysis of polystyrene (PS) and expandable polystyrene (EPS) pyrolysis of samples in Iran can help simulate waste recycling processes and consequently reduce the environmental problems.