Some kinetic and thermodynamic aspects of thermal degradation of lightly stabilised elastomers

摘要

The thermal stability of ethylene-propylene elastomers in the presence of light stabilizing antioxidant (Topanol OC) is studied. The oxygen uptake method was performed for determination of thermal oxidation in air atmosphere at constant temperatures (165 degrees C, 175 degrees C and 185 degrees C). The experimental unit used for oxygen uptake measurements is described. The dependence of absorbed oxygen on various oxidation times reveals marked dissimilarity between the two ethylene-propylene elastomers, because the terpolymer contains 3.5% ethylidene-norbornene. Changes in the activation energy of oxidation are evaluated over the whole process time. Free energy vs reaction time curves for all degradation experiments are presented and some remarks on entropy change for the overall process are made in order to explain oxygen-containing product accumulation. Using Arrhenius plots the durability of EPDM/Topanol OC system was calculated. (C) 1998 Elsevier Science Ltd. All rights reserved. [References: 18]