ARE KINETIC-PARAMETERS OF NONISOTHERMAL THERMOGRAVIMETRIC DEGRADATIONOF POLYMERS UNEQUIVOCAL

Due to the complex character of the thermal degradation of polymers as a solid-gas chain reaction, an unequivocal kinetic characterization i s possible only for stationary states of both radical concentration an d reaction mechanism. These conditions are hardly realizable in non-is othermal thermogravimetry. Additional the weight losses are dependent on the volatility of the reaction products. That is not always certain in polymer degradation. As a consequence the deduced 'kinetic paramet ers' are not unequivocal. They are conversion and heating rate depende nt and may be influenced by sample shape and size. Thus the 'kinetic p arameters' are in fact from the point of view of mathematics the fitti ng parameters of a 'rate equation' like relation, specific for the use d reaction conditions only. From the point of view of chemical kinetic s they are neither attributable to a determined reaction mechanism nor can they be used for predictions.