THERMOGRAVIMETRIC ANALYSIS OF POLYSTYRENE - INFLUENCE OF SAMPLE WEIGHT AND HEATING RATE ON THERMAL AND KINETIC-PARAMETERS

This article studies the influence of the heating rate and sample weig ht on the thermal decomposition of polystyrene (first-order kinetics). For this purpose, the kinetic parameters (i.e., frequency factor and activation energy), variables at the maximum decomposition rate (such as conversion, reaction rate, and temperature), as well as some charac teristic temperatures have been determined for a series of experiments where the heating rate varies (0.5-11.5 K/min) and also, the sample w eight (6.0-25.1 mg). Some mathematical equations have been developed t hat allow: (1) evaluation of the activation energy of thermal decompos ition by different ways and comparing the results obtained; (2) relati ng different parameters between themselves, such as the heating rate w ith the temperature at the maximum decomposition rate or the frequency factor with the heating rate and sample weight. Finally, some theoret ical explanations of the variation of thermal and kinetic parameters h ave been proposed. (C) 1996 John Wiley & Sons, Inc.