The Mechanical Activation of Rubbers (Oxidation under Mechanical Stress)

Abstract

Abstract In the practical application of rubber products, their fatigue characteristics, i.e., the rate of deterioration under repeated mechanical deformation, are frequently of wide importance. Work by several authors has established the fact that the fatigue effect increases significantly under the influence of oxygen, e.g., the fatigue resistance of rubber in an atmosphere of oxygen is many times lower than in an inert medium. It was found also that in the fatigue process, as in the thermal oxidation of rubber, the inhibitor is consumed. The cause of the more rapid deterioration of rubber with fatigue is the subject of discussion of the present work. Until now the effect of mechanical stresses on the oxidation processes has not been accurately determined. The present authors have investigated the effect of repeated deformations on the rate of oxidation of vulcanized butadiene-styrene rubber in different kinetic periods of the reaction (induction period, autocatalysis). In these experiments, particular attention was devoted to the microkinetics (kinetics of inhibited oxidation) of the inhibition method which was employed. The latter was used in the investigations of the kinetics of the consumption of the inhibitor (phenyl-β-naphthylamine) in the oxidation of rubber. Since in thermal oxidation, this process follows a linear law, the kinetic curve with respect to the time axis gives the rate of reaction. The latter approximates the rate of the initial reaction between the oxygen and the rubber, that is, the rate of initiation of oxidation (Wi) if all the original active centers are eliminated by the inhibitor.