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

The thermal stability of ethylene-propylene elastomers in the presence of l ight stabilizing antioxidant (Topanol OC) is studied. The oxygen uptake met hod 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 di ssimilarity between the two ethylene-propylene elastomers, because the terp olymer contains 3.5% ethylidene-norbornene. Changes in the activation energ y of oxidation are evaluated over the whole process time. Free energy vs re action time curves for all degradation experiments are presented and some r emarks on entropy change for the overall process are made in order to expla in oxygen-containing product accumulation. Using Arrhenius plots the durabi lity of EPDM/Topanol OC system was calculated. (C) 1998 Elsevier Science Lt d. All rights reserved.