The universality of Friedman's isoconversional analysis results in a model-less prediction of thermodegradation profiles

Through isoconversional analysis of thermogravimetric data using the differential Friedman approach, it was discovered that thermogravimetric profiles predicted by various reaction models, using kinetic parameters determined by isoconversional analysis, practically overlap over the entire conversion range. The reason for this behaviour lies in the fact that the kinetic model's contribution during the model integration is cancelled out by the pre-exponential factor value since the same concentration term appears in the numerators of the expression from which the pre-exponential factors' values were calculated. The observed phenomenon is hereby demonstrated by the analysis of PE degradation runs carried out at different heating rates. The results show it is possible to predict the degradation of various materials simply by correlation twins, i.e. the two functional relations between activation energy, apparent pre-exponential factor and conversion. (C) 2017 Elsevier B.V. All rights reserved.