Thermal degradation study of waste polyethylene terephthalate (PET) under inert and oxidative environments

Thermogravimetric analysis (TGA) of polyethylene terephthalate obtained from waste soft drink bottles (PET-SDB) was carried out under inert (nitrogen) as well as reactive (synthetic air) environments to evaluate the degradation behaviour and degradation kinetics. Non-isothermal TGA experiments at heating rates of 5, 10, 20, 40 and 50 degrees C/min were performed and the kinetic parameters such as activation energy (E-alpha) and pre-exponential factor (A(alpha)) were determined at various extent of conversions using advance isoconversional (AIC) method. Criados' master plot technique established F1 (first order) as possible reaction model (f(alpha)) for both inert and oxygenated non-isothermal TGA data. Under inert (N-2) environment a residue accumulation of around 20% was observed whereas complete conversion of PET-SDB occurred in oxygenated environment. The activation energy values were found in the range of 203-355 kJ/mol and 145-218 kJ/mol for inert and oxygenated environment respectively. Isothermal TGA data at various temperatures were analysed for the estimation of kinetic parameters. In the considered range of conversions, the range of activation energy obtained for multiple isothermal TGA data was found in the range of 196-217 kJ/mol.