RELIABILITY OF CONVERSION-TIME DEPENDENCIES AS PREDICTED FROM THERMAL-ANALYSIS DATA

The isothermal dependencies of the conversion on time can be predicted from data resulting from thermal analysis experiments performed under non-isothermal conditions. The reliability of the predictions depends on an approach used to define the kinetic triplet (the activation ene rgy, the pre-exponential factor and the reaction model). Five differen t approaches were examined and typical errors were pointed out. It was concluded that an approach (1) which uses only one thermal analysis e xperiment to define the kinetic triplet should not be used for predict ions. In the case of a single-step process the approaches suggested by , correspondingly, the ASTM E648 (2), Malek (3) and Vyazovkin (4) are applicable, but (2) leads to crucial errors when the process does not obey a first-order reaction. For a complex process approaches by Kaise rsberger and Opfermann (5) as well as (4) should be used. The predicti ons of (4) are expected to be more reliable because they are free from ambiguity which is peculiar to (5).