Chemical Engineering Journal 111 (2005) 39–43 Thermal degradation kinetics of poly(ethylene terephthalate) from waste soft drinks bottles B. Saha, A.K. Ghoshal ∗ Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati 39, Assam, India Received 11 February 2005; received in revised form 30 March 2005; accepted 1 April 2005 Abstract 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. © 2005 Elsevier B.V. All rights reserved. Keywords: Pyrolysis; TGA; PET; Thermal degradation; Heating rate 1. Introduction Packaging presents a major growth area where there has been an increasing demand for plastics and 52% of the plas- tics produced in India are utilized for packaging. Among the commodity plastics, polyethylene (PE) and polyethylene terephthalate (PET) are predominantly used in packaging. Low-density polyethylene (LDPE) is used in the manufac- ture of carry bags and PET is used in packaging beverages like soft drink and mineral water. PET in particular presents a major growth area in the years to come. Indian PET con- sumption has grown at an annual rate of 30% and the current PET consumption is estimated to be around 45,000 tonnes per annum [1]. India will probably see a rise in waste gen- eration from less than 40,000 metric tonnes per year to over 125,000 metric tonnes by the year 2030 [2]. ∗ Corresponding author. Tel.: +91 0361 2582252; fax: +91 0361 2690762. E-mail address: aloke@iitg.ernet.in (A.K. Ghoshal). The most common ways to treatment of the solid waste are land filling, incineration and materials recycling. A life cycle assessment (LCA) tool is used to compare different alterna- tive waste treatment strategies. The simulation model Orware (organic waste research) used for the material and energy flows in waste management based on life cycle assessment (LCA) was used in the quantification of emissions, energy use and financial costs. The results suggest the environmental preference of recycling over incineration over land filling [3]. The quality of recycled product remains questionable if poor state-of-the-art technologies are employed for recycling [1]. To overcome certain demerits of recycling and inciner- ation, researchers across the world have focused on devel- opment of value added products from waste plastics such as activated carbon, liquid fuel and gaseous product and monomer recovery [4–8]. Again, extensive research is going on to look for alternative energy sources. The application of novel alternative process, pyrolysis or catalytic degradation as a means of reusing scrap tyres and waste plastic, have recently been the subject of renewed interest. In this process 1385-8947/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2005.04.018