A kinetic study of the thermal decomposition of polyesters by controlled-rate thermogravimetry

A kinetic study of the thermal decomposition of engineering polyesters has been made by means of controlled-rate thermogravimetry (CRTG), a procedure that is a part of controlled-rate thermal analysis (CRTA). Various decomposition rates were used in the constant decomposition rate control (CDRC) experiments, in order to estimate the apparent activation energy without prior knowledge of the actual mechanism. The kinetic equations governing the thermal decomposition of poly(ethylene terphthalate) (PET) and poly(butylene terphthalate) (PBT) were determined. The kinetic parameters of these polyesters were estimated from both, the CDRC curve and evolved-gas components, obtained from the simultaneous TG-MS system, and corresponding to a kinetic-model-supported random scission of the main chain and with L=2. It is concluded that analytic techniques using the thermogravimetric traces obtained from different decomposition rates at CDRC are capable of establishing unique kinetic parameters. CRTG (CRTA) offers significant advantages in this field of study when dealing with thermal decomposition of polymers. (C) 1998 Elsevier Science B.V.