Thermal degradation kinetics of poly(ethylene terephthalate) from waste soft drinks bottles

To overcome certain demerits of recycling and incineration, researchers across the world have focused on development of value added products from waste plastics such as liquid and gaseous fuel, activated carbon and monomer recovery. Thermogravimetic analysis (TGA) is one of the widely used techniques to study the pyrolysis reaction kinetics. A kinetic model is necessary to predict the reactor behaviour as well as product range distribution. This paper investigates the thermal pyrolysis kinetics of poly(ethylene terephthalate) (PET) from different sources of soft drink bottles such as M/s Coca Cola and M/s Pepsi. Thermal degradation is carried out in dynamic condition at three different heating rates of 10, 15 and 25 K min(-1) under nitrogen atmosphere. A simple nth order kinetic model is proposed to study the thermal degradation of waste plastics. Kinetic parameters are obtained from three dynamic TGA curves at three different heating rates using ASTM E698 and from one TGA curve at the heating rate of 10 K min(-1) using nth order model techniques. PET pyrolysis exhibits 70-80% weight loss in the temperature range of 653-788 K. The nth order model technique better predicts the experimental data than ASTM E698 technique. Values of activation energy obtained by nth order model technique are 322.3 and 338.98 kJ/mole for Coca Cola and Pepsi samples, respectively. (c) 2005 Elsevier B.V All rights reserved.