Kinetics of the thermal degradation of polyethylene terephthalate

Abstract

A study of the kinetics of the thermal degradation of polyethylene terephthalate (PET) employing differential kinetic models and rapid computer analysis of thermogravimetric weight-loss data is presented. The influence of heating rate in non-isothermal degradation kinetics is investigated. The kinetic parameters for the pyrolysis of PET in inert atmosphere are presented. It is shown that the rate of degradation, activation energy, and pre-exponential factor depend strongly on heating rate whereas the order of reaction, found to be one, remains unchanged. Estimates of low temperature ( <300°C) isothermal kinetics, and hence isothermal stability of PET films, from non-isothermal kinetics are shown to be similarly dependent on the heating rates employed in dynamic thermogravimetry. The observed variation of kinetic parameters with heating rate is attributed to the coupling of physical transport processes with chemical processes.